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HVAC System - Compressor Clutch Controls: Other Chevrolet Malibu V facelift

A/c Compressor 39 illustrations ~54874 words

A/C COMPRESSOR CLUTCH CONTROLS (CARS)

To provide improved idle quality, improved Wide Open Throttle (WOT) performance and A/C system protection, the compressor clutch is controlled by PCM/ECM.

For proper control of cooling fans, compressor clutch, and Idle Air Control (IAC) valve, a refrigerant pressure sensor is used. The PCM/ECM uses signals provided by sensor to monitor high and low side refrigerant pressures. If PCM/ECM detects a fault in refrigerant pressure circuit, compressor clutch will be disabled.

The A/C clutch relay is controlled by PCM/ECM. This allows PCM/ECM to raise idle speed before engaging compressor clutch, or disable compressor clutch during WOT, high engine RPM, high power steering loads, and hot engine restarts. The PCM/ECM also disables compressor clutch if coolant temperature becomes excessive.

Note. This article ONLY contains those testing procedures required to test A/C compressor clutch control circuit. Other diagnostic information may be referenced while performing A/C compressor clutch control diagnosis. For additional information, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

ApplicationLocation
C BodyRight Front Of Engine Compartment, In Fuse/Relay Block
K BodyIn Underhood Fuse/Relay Block, On Right Side Of Engine Compartment
E BodyIn Underhood Fuse/Relay Block, On Left Side Of Engine Compartment
F BodyIn Underhood Electrical Center, In Left Front Of Engine Compartment
G BodyIn Underhood Relay Center, On Right Side Of Engine Compartment
H BodyIn Underhood Fuse Block, At Right Front Of Engine Compartment
J BodyIn Underhood Fuse/Relay Block, At Left Front Of Engine Compartment
N BodyIn Underhood Fuse/Relay Block, At Left Side Of Engine Compartment
V BodyLeft Front of Engine Compartment, In ECM Housing
W BodyIn Underhood Electrical Center, On Right Side Of Engine Compartment
Y BodyIn Underhood Electrical Center, In Front Of Battery

A/C CLUTCH RELAY LOCATION (CARS)

FWD Vans

To provide improved idle quality, maintain Wide Open Throttle (WOT) performance and provide A/C system protection, compressor clutch is controlled by PCM.

The A/C clutch relay is controlled by PCM according to information received from A/C pressure sensor and various other sensors. This allows the PCM to raise idle speed before engaging compressor clutch. PCM will disable compressor clutch during WOT, when refrigerant pressure is incorrect or if coolant temperature exceeds a predetermined value. The PCM inhibits compressor clutch operation when engine speed is greater than 4500 RPM for 5 seconds, or when throttle angle exceeds 90 percent.

RWD Trucks & Vans

The A/C clutch relay is controlled by PCM/VCM. The PCM/VCM improves idle quality by delaying compressor clutch engagement until idle speed is increased, or disengages compressor clutch when idle speed is too low. Compressor clutch is cycled by PCM/VCM. The PCM/VCM smooths cycling of compressor clutch by adding fuel the instant compressor clutch is applied.

ApplicationLocation
A & B SeriesIn Underhood Fuse/Relay Block, On Right Side Above Battery
C & K SeriesIn Underhood Fuse/Relay Center, On Left Side Of Engine Compartment
S & T SeriesIn Underhood Fuse Block, On Left Side Of Engine Compartment
G SeriesIn Underhood Fuse/Relay Center, Left Front Of Engine Compartment
L & M SeriesIn Underhood Fuse/Relay Center, Left Side Of Engine Compartment
U BodyIn Underhood Accessory Wiring Junction Block

A/C CLUTCH RELAY LOCATION (LIGHT TRUCKS & VANS)

2.2L & 2.4L: CAVALIER & SUNFIRE (2000)

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

2.2L & 2.4L: CAVALIER & SUNFIRE (2001)

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

Compressor Clutch Does Not Engage

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S23725843532001041200000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Turn A/C request switch to ON position. Turn air temperature switch to coldest position. Cycle mode switch through each position except off. If A/C compressor operates in each mode position, problem is intermittent. If A/C compressor does not operate in each mode position, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side STATIC pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C high side pressure sensor parameter in powertrain data list. Compare A/C high side pressure on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ), go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ), go to step 18 .
  5. If HVAC control assembly is inoperative, go to step 9 . If HVAC control assembly is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe A/C request parameter in powertrain data list 2. Turn blower motor switch to maximum position. Turn mode switch to recirculation position. If scan tool indicates A/C request parameter is YES, go to next step. If scan tool indicates A/C request parameter is not YES, go to step 11 .
  7. Using scan tool, observe A/C relay commanded parameter in powertrain data list 2. If scan tool indicates A/C relay commanded parameter is ON, go to next step. If scan tool does not indicates A/C relay commanded parameter is ON, go to step 28 .
  8. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 12 . If A/C compressor clutch relay does not turn on and off with each command, go to step 14 .
  9. Test ignition voltage circuit (Brown wire) to HVAC control assembly for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to next step.
  10. Check ground circuit (Black wire) to HVAC control assembly for open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 26 .
  11. Start engine. Turn mode switch to MAX A/C position. Using test light connected to ground, probe A/C request signal circuit (Light Green/Black wire) at Body Control Module (BCM). If test light is on, go to step 27 . If test light is off, go to step 16 .
  12. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using a test light connected to ground, probe switch side voltage supply circuit (Orange wire) of A/C compressor clutch relay connector. If test light is on, go to next step. If test light is off, go to step 21 .
  13. Connect fused jumper (10 amp) between switch side voltage circuit (Orange wire) of A/C compressor clutch relay connector and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch relay connector. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 24 . If A/C compressor clutch does not engage, go to step 17 .
  14. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using a test light connected to ground, probe coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay connector. If test light is on, go to next step. If test light is off, go to step 20 .
  15. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay connector and coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay connector. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 24 . If test light does not turn on and off with each command, go to step 22 .
  16. Check A/C request signal circuit (Light Green/Black wire) for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 26 .
  17. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 19 .
  18. Check ground circuit (Black wire) of A/C pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 23 .
  19. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 25 .
  20. Repair coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. After repairs, go to step 35 .
  21. Repair switch side voltage supply circuit (Orange wire) of A/C compressor clutch relay. After repairs, go to step 35 .
  22. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open, or short to ground. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 28 .
  23. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 29 .
  24. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 30 .
  25. Check A/C compressor clutch coil connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 31 .
  26. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 32 .
  27. Check BCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 33 .
  28. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 34 .
  29. Replace A/C high pressure switch. After repairs, go to step 35 .
  30. Replace A/C compressor clutch relay. After repairs, go to step 35 .
  31. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 35 .
  32. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 35 .
  33. Replace BCM. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. After repairs, go to step 35 .
  34. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  35. Operate system to verify repair.

Compressor Clutch Does Not Disengage

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S23725843532001041200000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Turn mode switch to OFF position. Place A/C request switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Using scan tool, observe A/C REQUEST parameter in POWERTRAIN DATA LIST 2. If scan tool indicates A/C REQUEST parameter is NO, go to next step. If scan tool does not indicate A/C REQUEST parameter is NO, go to step 6 .
  4. Using scan tool, observe A/C RELAY COMMANDED parameter in POWERTRAIN DATA LIST 2. If scan tool indicates A/C RELAY COMMANDED parameter is OFF, go to next step. If scan tool does not indicate A/C RELAY COMMAND parameter is OFF, go to step 14 .
  5. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. after repairs, go to step 20 . If problem was not found, go to step 7 .
  6. Turn ignition switch to ON position. Turn mode switch to OFF position. Using test light connected to ground, probe A/C request signal circuit (Light Green/Black wire) at BCM. If test light is on, go to step 9 . If test light is off, go to step 13 .
  7. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to step 10 . If A/C compressor clutch does not turn off, go to next step.
  8. Check A/C compressor clutch voltage supply circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 11 .
  9. Check A/C request signal circuit (Light Green/Black wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 12 .
  10. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 15 .
  11. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 16 .
  12. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 17 .
  13. Check BCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 18 .
  14. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 19 .
  15. Replace A/C compressor clutch relay. After repairs, go to step 20 .
  16. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 20 .
  17. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 20 .
  18. Replace BCM. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. After repairs, go to step 20 .
  19. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  20. Operate system to verify repair.

2.4L, 3.1L & 3.4L: ALERO, GRAND AM & MALIBU

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S09592288732001041300000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Turn A/C request switch to ON position. Turn air temperature switch to coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C high side pressure sensor parameter in powertrain data list. Compare A/C high side pressure on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ), go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ), go to step 18 .
  5. If HVAC control assembly is inoperative, go to step 9 . If HVAC control assembly is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe A/C request parameter in BCM data list 2. Turn blower motor switch to maximum position. Turn mode switch to VENT position. Place A/C request switch in ON position. If scan tool indicates A/C request parameter is YES, go to next step. If scan tool indicates A/C request parameter is not YES, go to step 11 .
  7. Using scan tool, observe A/C relay commanded parameter in powertrain data list 2. If scan tool indicates A/C relay commanded parameter is ON, go to next step. If scan tool does not indicates A/C relay commanded parameter is ON, go to step 28 .
  8. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 12 . If A/C compressor clutch relay does not turn on and off with each command, go to step 14 .
  9. Test ignition voltage circuit (Brown wire) to HVAC control assembly for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to next step.
  10. Check ground circuit (Black wire) to HVAC control assembly for open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 26 .
  11. Start engine. Place A/C request switch in ON position. Measure voltage between A/C request circuit (Light Green wire) at BCM and ground. If battery voltage is present, go to step 27 . If battery voltage is not present, go to step 16 .
  12. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using a test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay connector. If test light is on, go to next step. If test light is off, go to step 21 .
  13. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay connector and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch relay connector. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 24 . If A/C compressor clutch does not engage, go to step 17 .
  14. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using a test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay connector. If test light is on, go to next step. If test light is off, go to step 20 .
  15. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay connector and coil side voltage supply circuit of A/C compressor clutch relay connector. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 24 . If test light does not turn on and off with each command, go to step 22 .
  16. Check A/C request signal circuit (Light Green wire) for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 26 .
  17. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 19 .
  18. Check ground circuit (Black wire) of A/C pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 23 .
  19. Check ground circuit (Gray wire and Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 25 .
  20. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 35 .
  21. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 35 .
  22. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open, or short to ground. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 28 .
  23. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 29 .
  24. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 30 .
  25. Check A/C compressor clutch coil connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 31 .
  26. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 32 .
  27. Check BCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 33 .
  28. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 34 .
  29. Replace A/C high pressure switch. After repairs, go to step 35 .
  30. Replace A/C compressor clutch relay. After repairs, go to step 35 .
  31. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 35 .
  32. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 35 .
  33. Replace BCM. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. After repairs, go to step 35 .
  34. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  35. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S09592288732001041300000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Turn mode switch to OFF position. Place A/C request switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Using scan tool, observe A/C REQUEST parameter in POWERTRAIN DATA LIST 2. If scan tool indicates A/C REQUEST parameter is OFF, go to next step. If scan tool does not indicate A/C REQUEST parameter is OFF, go to step 6 .
  4. Using scan tool, observe A/C RELAY COMMANDED parameter in BODY CONTROL MODULE DATA LIST 2. If scan tool indicates A/C RELAY COMMANDED parameter is OFF, go to next step. If scan tool does not indicate A/C RELAY COMMAND parameter is OFF, go to step 14
  5. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. after repairs, go to step 20 . If problem was not found, go to step 7 .
  6. Start engine. Place A/C switch in OFF position. Measure voltage between A/C request circuit (Light Green wire) at BCM and ground. If battery voltage is present, go to step 9 . If battery voltage is not present, go to step 13 .
  7. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to step 10 . If A/C compressor clutch does not turn off, go to next step.
  8. Check A/C compressor clutch voltage supply circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 11 .
  9. Check A/C request signal circuit (Light Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 12 .
  10. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 15 .
  11. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 16 .
  12. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 17 .
  13. Check BCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 18 .
  14. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 19 .
  15. Replace A/C compressor clutch relay. After repairs, go to step 20 .
  16. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 20 .
  17. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 20 .
  18. Replace BCM. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. After repairs, go to step 20 .
  19. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  20. Operate system to verify repair.

3.0L: CATERA

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

Note. Catera is equipped with an anti-theft system. ECM must be programmed when replaced. See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT or COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S33664376692001041600000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place A/C switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to next step. If A/C compressor clutch relay does not turn on and off with each command, go to step 6 .
  5. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit (Red wire) of A/C compressor clutch relay. If test light is on, go to step 7 . If test light is off, go to step 17 .
  6. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit (Brown wire) of A/C compressor clutch relay. If test light is on, go to step 9 . If test light is off, go to step 16 .
  7. Connect fused jumper (10 amp) between switch side voltage circuit (Red wire) of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Green wire) of A/C compressor clutch. Turn ignition to ON position, with engine off. If A/C compressor clutch engages, go to step 18 . If A/C compressor clutch does not engage, go to next step.
  8. Check A/C compressor clutch supply voltage circuit (Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 26 . If problem was not found, go to step 13 .
  9. Connect test light between control circuit (Brown/Purple wire) of A/C compressor clutch relay and coil side voltage supply circuit (Brown wire) of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 18 . If test light does not turn on and off with each command, go to next step.
  10. If test light remains on with each command, go to next step. If test light does not remain on with each command, go to step 12 .
  11. Check control circuit (Brown/Purple wire) and A/C cut out input circuit (Yellow/Blue wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 26 . If problem was not found, go to step 19 .
  12. Check control circuit (Brown/Purple wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 26 . If problem was not found, go to step 19 .
  13. Check ground circuit (Brown/Black wire) between A/C compressor clutch and secondary cooling fan temperature switch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 26 . If problem was not found, go to next step.
  14. Check ground circuit (Black wire) of secondary cooling fan temperature switch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 26 . If problem was not found, go to next step.
  15. Ensure engine coolant temperature is less than 248°F (120°C). Measure resistance between switch side, secondary cooling fan temperature switch terminals. If resistance is near zero, go to step 20 . If resistance is not near zero, go to step 21 .
  16. Repair coil side voltage supply circuit (Brown wire) of A/C compressor clutch relay. After repairs, go to step 26 .
  17. Repair switch side voltage supply circuit (Red wire) of A/C compressor clutch relay. After repairs, go to step 26 .
  18. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 26 . If problem was not found, go to step 22 .
  19. Check ECM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 26 . If problem was not found, go to step 25 .
  20. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 26 . If problem was not found, go to step 24 .
  21. Check secondary cooling fan temperature switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 26 . If problem was not found, go to step 23 .
  22. Replace A/C compressor clutch relay. After repairs, go to step 26 .
  23. Replace secondary cooling fan temperature switch. After repairs, go to step 26 .
  24. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 26 .
  25. Replace ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  26. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S33664376692001041600000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Place A/C request switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to next step. If A/C compressor clutch does not turn off, go to step 5 .
  4. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to step 6 . If resistance is not infinite, go to step 7 .
  5. Check A/C compressor clutch supply voltage circuit (Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 12 . If problem was not found, go to step 10 .
  6. Check A/C clutch relay control circuit (Brown/Purple wire) to ECM and A/C cut out input circuit (Yellow/Blue wire) to A/C-heater control for short to ground. If problem was found, repair as necessary. After repairs, go to step 12 . If problem was not found, go to step 8 .
  7. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 12 . If problem was not found, go to step 9 .
  8. Check ECM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 12 . If problem was not found, go to step 11 .
  9. Replace A/C compressor clutch relay. After repairs, go to step 12 .
  10. Replace the A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 12 .
  11. Replace ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  12. Operate system to verify repair.

3.1L, 3.5L & 3.8L: CENTURY, INTRIGUE & REGAL

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

Compressor Clutch Does Not Engage (Automatic A/C)

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S30845500222001041700000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place A/C switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C high side pressure on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 15 .
  5. HVAC control module is inoperative when module does not respond to any operator control requests. If HVAC control module is inoperative, go to step 14 . If HVAC control module is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe A/C REQUEST parameter in POWERTRAIN data list. Turn air temperature switch to coldest position. Place A/C REQUEST switch in ON position. If scan tool indicates A/C REQUEST parameter is YES, go to next step. If scan tool does not indicate A/C request is YES, go to step 26 .
  7. Using scan tool, observe A/C RELAY COMMAND status in POWERTRAIN Data List. If scan tool indicates A/C RELAY COMMAND status is ON, go to next step. If scan tool does not indicate A/C RELAY COMMAND status is ON, go to step 27 .
  8. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 12 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  9. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 22 .
  10. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and the coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 24 . If test light does not turn on and off with each command, go to next step.
  11. If test light remains on with each command, go to step 18 . If test light does not remain on with each command, go to step 17 .
  12. Turn ignition switch to off position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is not on, go to step 21 .
  13. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 24 . If A/C compressor clutch does not engage, go to step 19 .
  14. Check ignition voltage circuit (Brown wire) of HVAC control assembly for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 16 .
  15. Check ground circuit (Black wire) of A/C pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 23 .
  16. Check ground circuit (Black wire) of HVAC control module for open. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 26 .
  17. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 27 .
  18. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 27 .
  19. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to next step.
  20. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 25 .
  21. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 33 .
  22. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 33 .
  23. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 28 .
  24. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 29 .
  25. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 30 .
  26. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 31 .
  27. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 32 .
  28. Replace A/C high pressure switch. After repairs, go to step 33 .
  29. Replace A/C compressor clutch relay. After repairs, go to step 33 .
  30. Replace the A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 33 .
  31. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 33 .
  32. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  33. Operate system to verify repair.

Compressor Clutch Does Not Engage (Manual A/C)

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S30845500222001041700000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place A/C switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C high side pressure on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 17 .
  5. If HVAC control module is inoperative, go to step 16 . If HVAC control module is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe A/C REQUEST parameter in POWERTRAIN data list. Turn air temperature switch to coldest position. Turn blower motor to ON position. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST parameter is ON, go to step 10 . If scan tool does not indicate A/C REQUEST parameter is ON, go to next step.
  7. If A/C request indicator illuminates, go to step 9 . If A/C request indicator does not illuminate, go to next step.
  8. Ensure blower motor switch is ON position. Turn ignition switch to ON position. Check blower motor off circuit (Dark Green wire) at HVAC control assembly for short to voltage. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 28 .
  9. Turn ignition to off position. Check A/C request signal circuit (Dark Green/White wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 29 .
  10. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 14 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  11. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 23 .
  12. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 24 . If test light does not turn on and off with each command, go to next step.
  13. If test light remains on with each command, go to step 20 . If test light does not remain on with each command, go to step 19 .
  14. Turn ignition switch to off position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 24 .
  15. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 26 . If A/C compressor clutch does not engage, go to step 21 .
  16. Check ignition voltage circuit (Brown wire) of HVAC control module for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 18 .
  17. Check ground circuit (Black wire) of A/C pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 25 .
  18. Check ground circuit (Black wire) of HVAC control module for open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 28 .
  19. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 29 .
  20. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 29 .
  21. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to next step.
  22. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 27 .
  23. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 35 .
  24. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 35 .
  25. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 30 .
  26. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 31 .
  27. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 32 .
  28. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 33 .
  29. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 34 .
  30. Replace A/C high pressure switch. After repairs, go to step 35 .
  31. Replace A/C compressor clutch relay. After repairs, go to step 35 .
  32. Replace the A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 35 .
  33. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 35 .
  34. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  35. Operate system to verify repair.

Compressor Clutch Does Not Disengage (Automatic A/C)

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S30845500222001041700000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Turn blower motor switch to OFF position. Place A/C request switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Using scan tool, observe A/C RELAY COMMAND STATUS in POWERTRAIN data list. If scan tool indicates A/C RELAY COMMAND STATUS is ON, go to next step. If scan tool does not indicate A/C RELAY COMMAND STATUS is ON, go to step 5 .
  4. Using scan tool, observe A/C REQUEST parameter in the POWERTRAIN data list. If scan tool indicates A/C REQUEST parameter is YES, go to step 10 . If scan tool does not indicate A/C REQUEST parameter is YES, go to step 11 .
  5. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to next step. If A/C compressor clutch does not turn off, go to step 8 .
  6. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 9 .
  7. Check A/C clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 11 .
  8. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 13 .
  9. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 12 .
  10. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 14 .
  11. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 15 .
  12. Replace A/C compressor clutch relay. After repairs, go to step 16 .
  13. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 16 .
  14. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 16 .
  15. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  16. Operate system to verify repair.

Compressor Clutch Does Not Disengage (Manual A/C)

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S30845500222001041700000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Turn blower motor switch to OFF position. Place A/C request switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Using scan tool, observe A/C REQUEST parameter in POWERTRAIN data list. If scan tool indicates A/C REQUEST parameter is ON, go to next step. If scan tool does not indicate A/C REQUEST parameter is ON, go to step 6 .
  4. Check A/C request signal circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to next step.
  5. Turn ignition switch to OFF position. Back out terminal for A/C request circuit (Dark Green/White wire) at HVAC control head. Start engine. Using scan tool, observe A/C REQUEST parameter. If scan tool indicates A/C REQUEST parameter is ON, go to step 12 . If scan tool does not indicate A/C REQUEST parameter is ON, go to step 11 .
  6. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to next step. If A/C compressor clutch does not turn off, go to step 9 .
  7. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 10 .
  8. Check A/C clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 12 .
  9. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 14 .
  10. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 13 .
  11. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 15 .
  12. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 16 .
  13. Replace A/C compressor clutch relay. After repairs, go to step 17 .
  14. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 17 .
  15. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 17 .
  16. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  17. Operate system to verify repair.

3.1L & 3.8L: GRAND PRIX

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

Compressor Does Not Engage

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S10234515812001041700000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place A/C switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C high side pressure on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 18 .
  5. If HVAC control module is inoperative, go to step 17 . If HVAC control module is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe A/C REQUEST parameter in ENGINE DATA 2 data list. Turn air temperature switch to coldest position. Turn blower motor to ON position. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST parameter is ON, go to step 11 . If scan tool does not indicate A/C REQUEST parameter is ON, go to next step.
  7. If A/C request indicator illuminates, go to step 9 . If A/C request indicator does not illuminate, go to next step.
  8. Ensure blower motor switch is in ON position. Turn ignition switch to ON position. Check blower motor off circuit (Dark Green wire) at HVAC control assembly for short to voltage. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 29 .
  9. Turn ignition switch to OFF position. Disconnect PCM. Turn ignition switch to ON position, with engine off. Turn air temperature switch to coldest position. Turn blower motor switch to maximum speed position. Place A/C request switch in ON position. Measure voltage between A/C request signal circuit (Dark Green/White wire) of PCM and ground. If voltage is 10-12.5 volts, go to step 30 . If voltage is not 10-12.5 volts, go to next step.
  10. Turn ignition switch to OFF position. Check A/C request signal circuit (Dark Green/White wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 29 .
  11. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 15 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  12. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 25 .
  13. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 27 . If test light does not turn on and off with each command, go to next step.
  14. If test light remains on with each command, go to step 21 . If test light does not remain on with each command, go to step 20 .
  15. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 24 .
  16. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 27 . If A/C compressor clutch does not engage, go to step 22 .
  17. Test ignition voltage circuit (Brown wire) of HVAC control module for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 19 .
  18. Check ground circuit (Black wire) of A/C refrigerant pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 26 .
  19. Check ground circuit (Black wire) of HVAC control module for open. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 29 .
  20. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 30 .
  21. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 30 .
  22. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to next step.
  23. Check ground circuit (Black wire) of A/C compressor clutch for a high resistance or open. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 28 .
  24. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 36 .
  25. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 36 .
  26. Check A/C refrigerant pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 31 .
  27. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 32 .
  28. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 33 .
  29. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 34 .
  30. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 36 . If problem was not found, go to step 35 .
  31. Replace A/C refrigerant pressure sensor. After repairs, go to step 36 .
  32. Replace A/C compressor clutch relay. After repairs, go to step 36 .
  33. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 36 .
  34. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 36 .
  35. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  36. Operate system to verify repair.

Compressor Does Not Disengage

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S10234515812001041700000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Turn blower motor switch to OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Using scan tool, observe A/C REQUEST parameter in ENGINE DATA 2 data list. If scan tool indicates A/C REQUEST parameter is ON, go to next step. If scan tool does not indicate A/C REQUEST parameter is ON, go to step 6 .
  4. Check A/C request signal circuit (Dark Green/White wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to next step.
  5. Turn ignition switch to OFF position. Disconnect HVAC control module. Back out terminal for A/C request circuit (Dark Green/White wire) at HVAC control head. Start engine. Using scan tool, observe A/C REQUEST parameter. If scan tool indicates A/C REQUEST parameter is ON, go to step 12 . If scan tool does not indicate A/C REQUEST parameter is ON, go to step 11 .
  6. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to next step. If A/C compressor clutch does not turn off, go to step 9 .
  7. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 10 .
  8. Check A/C clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 12 .
  9. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 14 .
  10. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 13 .
  11. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 15 .
  12. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 16 .
  13. Replace A/C compressor clutch relay. After repairs, go to step 17 .
  14. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 17 .
  15. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 17 .
  16. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  17. Operate system to verify repair.

3.1L: LUMINA

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

3.4L & 3.8L: IMPALA & MONTE CARLO

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S28218626972001041800000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place A/C switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C high side pressure on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 18 .
  5. If HVAC control assembly is inoperative, go to step 9 . If HVAC control assembly is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter in POWERTRAIN DATA LIST 2. Turn blower motor switch to maximum speed position. Turn mode switch to MAX air position. Place A/C switch in ON position. If scan tool indicates A/C REQUEST parameter is YES, go to next step. If scan tool does not indicate A/C REQUEST parameter is YES, go to step 11 .
  7. Using scan tool, observe COMMANDED A/C parameter in POWERTRAIN DATA LIST 2. If scan tool indicates COMMANDED A/C parameter is ON, go to next step. If scan tool does not indicate COMMANDED A/C parameter is ON, go to step 28 .
  8. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 12 . If A/C compressor clutch relay does not turn on and off with each command, go to step 14 .
  9. Check ignition voltage circuit (Brown wire) to HVAC control assembly for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to next step.
  10. Check ground circuit (Black wire) to HVAC control assembly for open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 26 .
  11. Using scan tool, observe A/C SWITCH parameter in BCM INPUTS. If scan tool indicates A/C SWITCH parameter is ON, go to step 27 . If scan tool does not indicate A/C SWITCH parameter is ON, go to step 16 .
  12. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit (Orange wire) of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 21 .
  13. Connect fused jumper (10 amp) between switch side voltage circuit (Orange wire) of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. If A/C compressor clutch engages, go to step 24 . If A/C compressor clutch does not engage, go to step 17 .
  14. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 20 .
  15. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 24 . If test light does not turn on and off with each command, go to step 22 .
  16. Check A/C request signal circuit (Dark Green/White) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 26 .
  17. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 19 .
  18. Check ground circuit (Black wire) of A/C pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 23 .
  19. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 25 .
  20. Repair coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. After repairs, go to step 35 .
  21. Repair switch side voltage supply circuit (Orange wire) of A/C compressor clutch relay. After repairs, go to step 35 .
  22. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open, or short to ground. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 28 .
  23. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 29 .
  24. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 30 .
  25. Check A/C compressor clutch coil connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 31 .
  26. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 32 .
  27. Check BCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 33 .
  28. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 34 .
  29. Replace A/C high pressure switch. After repairs, go to step 35 .
  30. Replace A/C compressor clutch relay. After repairs, go to step 35 .
  31. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 35 .
  32. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 35 .
  33. Replace BCM. See REMOVAL & INSTALLATION in appropriate BODY CONTROL MODULES article. After repairs, go to step 35 .
  34. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  35. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S28218626972001041800000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Turn blower motor switch to OFF position. Place A/C request switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Using scan tool, observe A/C REQUEST parameter in POWERTRAIN DATA LIST 2. If scan tool indicates A/C REQUEST parameter is OFF, go to next step. If A/C REQUEST parameter is not OFF, go to step 6 .
  4. Using scan tool, observe COMMANDED A/C parameter in POWERTRAIN DATA LIST 2. If scan tool indicates COMMANDED A/C parameter is OFF, go to next step. If scan tool does not indicate A/C COMMAND parameter is OFF, go to step 14 .
  5. Check control circuit (Dark Green wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 7 .
  6. Using scan tool, observe A/C SWITCH parameter in BCM INPUTS. If scan tool indicates A/C SWITCH parameter is ON, go to step 9 . If scan tool does not indicate A/C SWITCH parameter is ON, go to step 13 .
  7. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to step 10 . If A/C compressor clutch does not turn off, go to next step.
  8. Check A/C compressor clutch voltage supply circuit (Dark Green wire) at A/C compressor clutch for short to voltage. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 11 .
  9. Check A/C request signal circuit (Dark Green/White wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 12 .
  10. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 15 .
  11. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 16 .
  12. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 17 .
  13. Check BCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 18 .
  14. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 19 .
  15. Replace A/C compressor clutch relay. After repairs, go to step 20 .
  16. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 20 .
  17. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 20 .
  18. Replace BCM. See REMOVAL & INSTALLATION in appropriate BODY CONTROL MODULES article. After repairs, go to step 20 .
  19. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  20. Operate system to verify repair.

3.5L & 4.0L: AURORA

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S26243753252001041900000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place mode switch in DEFROST position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C high side pressure on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 20 .
  5. If HVAC control module is inoperative, go to step 19 . If HVAC control module is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe COMMANDED A/C parameter in POWERTRAIN data list. Turn air temperature switch to coldest position. If scan tool indicates COMMANDED A/C parameter is ON, go to step 13 . If scan tool does not indicate COMMANDED A/C parameter is ON, go to next step.
  7. Using scan tool, observe A/C CLUTCH (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool indicates A/C CLUTCH (DESIRED) parameter is ON, go to next step. If scan tool does not indicate A/C CLUTCH (DESIRED) parameter is ON, go to step 9 .
  8. Using scan tool, observe A/C CLUTCH (ACTUAL) parameter in DIM A/C INFORMATION list. If scan tool indicates A/C CLUTCH (ACTUAL) parameter is ON, go to step 13 . If scan tool does not indicate A/C CLUTCH (ACTUAL) parameter is ON, go to step 34 .
  9. Using scan tool, observe CONTROL HEAD (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool indicates CONTROL HEAD (DESIRED) parameter is ON, go to next step. If scan tool does not indicate CONTROL HEAD (DESIRED) parameter is ON, go to step 12 .
  10. Using scan tool, observe PRESSURE STATUS parameter in DIM A/C INFORMATION list. If scan tool indicates PRESSURE STATUS parameter is NORMAL, go to next step. If scan tool does not indicate PRESSURE STATUS parameter is NORMAL, problem is intermittent.
  11. Using scan tool, observe TEMPERATURE STATUS parameter in DIM A/C INFORMATION list. If scan tool indicates TEMPERATURE STATUS parameter is OK, go to step 31 . If scan tool does not indicate TEMPERATURE STATUE parameter is OK, check engine for overheating.
  12. Using scan tool, observe A/C CONTROL HEAD (DESIRED) parameter in DIM A/C INFORMATION list. Turn mode switch to and from DEFROST position. If scan tool indicates A/C CONTROL HEAD (DESIRED) parameter turns on and off with each command, go to step 30 . If scan tool does not indicate A/C CONTROL HEAD (DESIRED) parameter turns on and off with each command, go to step 33 .
  13. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 17 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  14. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 27 .
  15. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 29 . If test light does not turn on and off with each command, go to next step.
  16. If test light remains on with each command, go to step 23 . If test light does not remain on with each command, go to step 22 .
  17. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 26 .
  18. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 29 . If A/C compressor clutch does not engage, go to step 24 .
  19. Check ignition voltage circuit (Brown wire and Orange wire) of HVAC control module for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 21 .
  20. Check ground circuit (Black wire) of A/C pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 28 .
  21. Check ground circuit (Black wire) of HVAC control module for open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 33 .
  22. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 34 .
  23. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 34 .
  24. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to next step.
  25. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 32 .
  26. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 42 .
  27. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 42 .
  28. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 37 .
  29. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 38 .
  30. Check IPM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 35 .
  31. Check DIM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 36 .
  32. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 39 .
  33. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 40 .
  34. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 41 .
  35. Replace IPM. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. After repairs, go to step 42 .
  36. Replace DIM. See REMOVAL & INSTALLATION in appropriate BODY CONTROL MODULES article. After repairs, go to step 42 .
  37. Replace A/C high pressure switch. After repairs, go to step 42 .
  38. Replace A/C compressor clutch relay. After repairs, go to step 42 .
  39. Replace A/C compressor. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 42 .
  40. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 42 .
  41. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  42. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S26243753252001041900000) . If diagnostic system check has been performed, go to next step.
  2. Install scan tool. Turn ignition switch to ON position, with engine off. Using scan tool, command A/C relay on and off. If A/C compressor clutch engages and disengages with each command, go to next step. If A/C compressor clutch does not engage and disengage with each command, go to step 7 .
  3. Start engine. Place A/C request switch in OFF position. Using scan tool, observe COMMANDED A/C parameter in PCM ENGINE data list. If scan tool displays OFF, go to step 12 . If scan tool does not display OFF, go to next step.
  4. Using scan tool, observe CONTROL HEAD (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool displays A/C OFF, go to next step. If scan tool does not display A/C OFF, go to step 6 .
  5. Using scan tool, observe A/C CLUTCH (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool displays OFF, go to step 12 . If scan tool does not display OFF, go to step 11 .
  6. Using scan tool, observe A/C REQUESTED parameter in IPM HVAC SYSTEM data list. If scan tool displays NO, go to step 11 . If scan tool does not display NO, go to step 10 .
  7. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. If A/C compressor clutch disengages, go to step 13 . If A/C compressor clutch does not disengage, go to next step.
  8. Disconnect A/C compressor. If A/C compressor clutch disengages, go to next step. If A/C compressor clutch does not disengage, go to step 14 .
  9. Repair short to voltage in A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C relay. After repairs, go to step 18 .
  10. Check IPM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 18 . If problem was not found, go to step 15 .
  11. Check DIM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 18 . If problem was not found, go to step 16 .
  12. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 18 . If problem was not found, go to step 17 .
  13. Replace A/C compressor clutch relay. After repairs, go to step 18 .
  14. Replace A/C compressor. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 18 .
  15. Replace IPM. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. After repairs, go to step 18 .
  16. Replace DIM. See REMOVAL & INSTALLATION in appropriate BODY CONTROL MODULES article. After repairs, go to step 18 .
  17. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  18. Operate system to verify repair.

3.8L: BONNEVILLE & LESABRE

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK (AUTOMATIC A/C)»(ref-96385-S23054567182001042000000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place mode switch in DEFROST position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C high side pressure on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 20 .
  5. If HVAC control module is inoperative, go to step 19 . If HVAC control module is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe COMMANDED A/C parameter in POWERTRAIN data list. Turn air temperature switch to coldest position. If scan tool indicates COMMANDED A/C parameter is ON, go to step 13 . If scan tool does not indicate COMMANDED A/C parameter is ON, go to next step.
  7. Using scan tool, observe A/C CLUTCH (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool indicates A/C CLUTCH (DESIRED) parameter is ON, go to next step. If scan tool does not indicate A/C CLUTCH (DESIRED) parameter is ON, go to step 9 .
  8. Using scan tool, observe A/C CLUTCH (ACTUAL) parameter in DIM A/C INFORMATION list. If scan tool indicates A/C CLUTCH (ACTUAL) parameter is ON, go to step 13 . If scan tool does not indicate A/C CLUTCH (ACTUAL) parameter is ON, go to step 34 .
  9. Using scan tool, observe CONTROL HEAD (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool indicates CONTROL HEAD (DESIRED) parameter is ON, go to next step. If scan tool does not indicate CONTROL HEAD (DESIRED) parameter is ON, go to step 12 .
  10. Using scan tool, observe PRESSURE STATUS parameter in DIM A/C INFORMATION list. If scan tool indicates PRESSURE STATUS parameter is NORMAL, go to next step. If scan tool does not indicate PRESSURE STATUS parameter is NORMAL, problem is intermittent.
  11. Using scan tool, observe TEMPERATURE STATUS parameter in DIM A/C INFORMATION list. If scan tool indicates TEMPERATURE STATUS parameter is okay, go to step 31 . If scan tool does not indicate TEMPERATURE STATUS parameter is okay, check engine for overheating.
  12. Using scan tool, observe A/C CONTROL HEAD (DESIRED) parameter in DIM A/C INFORMATION list. Turn mode switch to and from DEFROST position. If scan tool indicates A/C CONTROL HEAD (DESIRED) parameter turns on and off with each command, go to step 30 . If scan tool does not indicate A/C CONTROL HEAD (DESIRED) parameter turns on and off with each command, go to step 33 .
  13. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 17 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  14. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 27 .
  15. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 29 . If test light does not turn on and off with each command, go to next step.
  16. If test light remains on with each command, go to step 23 . If test light does not remain on with each command, go to step 22 .
  17. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 26 .
  18. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 29 . If A/C compressor clutch does not engage, go to step 24 .
  19. Check ignition voltage circuit (Brown wire and Orange wire) of HVAC control module for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 21 .
  20. Check ground circuit (Black wire) of A/C pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 28 .
  21. Check ground circuit (Black wire) of HVAC control module for open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 33 .
  22. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 34 .
  23. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 34 .
  24. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to next step.
  25. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 32 .
  26. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 42 .
  27. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 42 .
  28. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 37 .
  29. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 38 .
  30. Check IPM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 35 .
  31. Check DIM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 36 .
  32. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 39 .
  33. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 40 .
  34. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 41 .
  35. Replace IPM. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. After repairs, go to step 42 .
  36. Replace DIM. See REMOVAL & INSTALLATION in appropriate BODY CONTROL MODULES article. After repairs, go to step 42 .
  37. Replace A/C high pressure switch. After repairs, go to step 42 .
  38. Replace A/C compressor clutch relay. After repairs, go to step 42 .
  39. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 42 .
  40. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 42 .
  41. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  42. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK (MANUAL A/C)»(ref-96385-S16107744442001042000000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place bi-level in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C high side pressure on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 24 .
  5. If HVAC control module is inoperative, go to step 19 . If HVAC control module is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe COMMANDED A/C parameter in POWERTRAIN data list. Turn air temperature switch to coldest position. Place bi-level switch in ON position. If scan tool indicates COMMANDED A/C parameter is ON, go to step 13 . If scan tool does not indicate COMMANDED A/C parameter is ON, go to next step.
  7. Using scan tool, observe A/C CLUTCH (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool indicates A/C CLUTCH (DESIRED) parameter is ON, go to next step. If scan tool does not indicate A/C CLUTCH (DESIRED) parameter is ON, go to step 9 .
  8. Using scan tool, observe A/C CLUTCH (ACTUAL) parameter in DIM A/C INFORMATION list. If scan tool indicates A/C CLUTCH (ACTUAL) parameter is ON, go to step 13 . If scan tool does not indicate A/C CLUTCH (ACTUAL) parameter is ON, go to step 33 .
  9. Using scan tool, observe CONTROL HEAD (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool indicates CONTROL HEAD (DESIRED) parameter is ON, go to next step. If scan tool does not indicate CONTROL HEAD (DESIRED) parameter is ON, go to step 12 .
  10. Using scan tool, observe PRESSURE STATUS parameter in DIM A/C INFORMATION list. If scan tool indicates PRESSURE STATUS parameter is NORMAL, go to next step. If scan tool does not indicate PRESSURE STATUS parameter is NORMAL, problem is intermittent.
  11. Using scan tool, observe TEMPERATURE STATUS parameter in DIM A/C INFORMATION list. If scan tool indicates TEMPERATURE STATUS parameter is OK, go to step 30 . If scan tool does not indicate TEMPERATURE STATUE parameter is OK, check engine for overheating.
  12. Using scan tool, observe A/C CONTROL HEAD (DESIRED) parameter in DIM A/C INFORMATION list. Turn mode switch to and from DEFROST position. If scan tool indicates A/C CONTROL HEAD (DESIRED) parameter turns on and off with each command, go to step 30 . If scan tool does not indicate A/C CONTROL HEAD (DESIRED) parameter turns on and off with each command, go to step 32 .
  13. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 17 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  14. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 27 .
  15. Connect test light between control circuit (Dark Green/White wire) and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 29 . If test light does not turn on and off with each command, go to next step.
  16. If test light remains on with each command, go to step 22 . If test light does not remain on with each command, go to step 21 .
  17. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 26 .
  18. Connect fused jumper (10 amp) between switch side voltage circuit and supply voltage circuit (Dark Green wire) of A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 29 . If A/C compressor clutch does not engage, go to step 23 .
  19. Check ignition voltage circuit (Brown wire) of HVAC control assembly for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to next step.
  20. Check ground circuit (Black wire) of HVAC control assembly for open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 32 .
  21. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 33 .
  22. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 33 .
  23. Check supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 25 .
  24. Check ground circuit (Black wire) of A/C pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 28 .
  25. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 31 .
  26. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 40 .
  27. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 40 .
  28. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 35 .
  29. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 36 .
  30. Check DIM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 34 .
  31. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 37 .
  32. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 38 .
  33. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 39 .
  34. Replace DIM. See REMOVAL & INSTALLATION in appropriate BODY CONTROL MODULES article. After repairs, go to step 40 .
  35. Replace A/C high pressure switch. After repairs, go to step 40 .
  36. Replace A/C compressor clutch relay. After repairs, go to step 40 .
  37. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 40 .
  38. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 40 .
  39. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  40. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK (AUTOMATIC A/C)»(ref-96385-S23054567182001042000000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Turn blower motor switch to OFF position. Place A/C switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor clutch does not operate, problem is intermittent.
  3. Using scan tool, observe A/C RELAY COMMANDED parameter in PCM data list. If scan tool indicates A/C RELAY COMMANDED parameter is ON, go to next step. If scan tool does not indicate A/C RELAY COMMANDED parameter is ON, go to step 7 .
  4. Using scan tool, observe A/C CONTROL HEAD (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool displays OFF, go to next step. If scan tool does not display OFF, go to step 12 .
  5. Using scan tool, observe A/C REQUESTED parameter in IPM HVAC SYSTEM data list. If scan tool displays YES, go to next step. If scan tool does not display YES, go to step 13 .
  6. Using scan tool, observe A/C CLUTCH (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool displays OFF, go to step 15 . If scan tool does not display OFF, go to step 14 .
  7. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position. If A/C compressor clutch disengages, go to next step. If A/C compressor clutch does not disengage, go to step 9 .
  8. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to step 11 .
  9. Check A/C compressor clutch voltage supply circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to next step.
  10. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to step 17 .
  11. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to step 16 .
  12. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to step 18 .
  13. Check IPM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to step 19 .
  14. Check DIM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to step 20 .
  15. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to step 21 .
  16. Replace A/C compressor clutch relay. After repairs, go to step 22 .
  17. Replace A/C compressor clutch hub and plate. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 22 .
  18. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 22 .
  19. Replace IPM. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. After repairs, go to step 22 .
  20. Replace DIM. See REMOVAL & INSTALLATION in appropriate BODY CONTROL MODULES article. After repairs, go to step 22 .
  21. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  22. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK (MANUAL A/C)»(ref-96385-S16107744442001042000000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Turn blower motor switch to OFF position. Place bi-level switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor clutch does not operate, problem is intermittent.
  3. Using scan tool, observe COMMANDED A/C parameter in POWERTRAIN data list. If scan tool indicates COMMANDED A/C parameter is ON, go to next step. If scan tool does not indicate COMMANDED A/C parameter is ON, go to step 6 .
  4. Using scan tool, observe A/C CONTROL HEAD (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool displays OFF, go to next step. If scan tool does not display OFF, go to step 11 .
  5. Using scan tool, observe A/C CLUTCH (DESIRED) parameter in DIM A/C INFORMATION List. If scan tool displays OFF, go to step 13 . If scan tool does not display OFF, go to step 12 .
  6. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position. If A/C compressor clutch disengages, go to next step. If A/C compressor clutch does not disengage, go to step 8 .
  7. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 10 .
  8. Check A/C compressor clutch voltage supply circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to next step.
  9. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 15 .
  10. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 14 .
  11. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 16 .
  12. Check DIM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 17 .
  13. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 18 .
  14. Replace A/C compressor clutch relay. After repairs, go to step 19 .
  15. Replace A/C compressor clutch hub and plate. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 19 .
  16. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 19 .
  17. Replace DIM. See REMOVAL & INSTALLATION in appropriate BODY CONTROL MODULES article. After repairs, go to step 19 .
  18. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  19. Operate system to verify repair.

3.8L: PARK AVENUE

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S31919908972001042000000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place mode switch in DEFROST position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C HIGH SIDE PRESSURE on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 23 .
  5. If HVAC control module is inoperative, go to step 19 . If HVAC control module is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe COMMANDED A/C parameter in POWERTRAIN data list. Turn air temperature switch to coldest position. If scan tool indicates COMMANDED A/C parameter is ON, go to step 13 . If scan tool does not indicate COMMANDED A/C parameter is ON, go to next step.
  7. Using scan tool, observe A/C CLUTCH (DESIRED) parameter in BCM A/C INFORMATION list. If scan tool indicates A/C CLUTCH (DESIRED) parameter is ON, go to next step. If scan tool does not indicate A/C CLUTCH (DESIRED) parameter is ON, go to step 9 .
  8. Using scan tool, observe A/C CLUTCH (ACTUAL) parameter in BCM A/C INFORMATION list. If scan tool indicates A/C CLUTCH (ACTUAL) parameter is ON, go to step 13 . If scan tool does not indicate A/C CLUTCH (ACTUAL) parameter is ON, go to step 34 .
  9. Using scan tool, observe CONTROL HEAD (DESIRED) parameter in BCM A/C INFORMATION list. If scan tool indicates CONTROL HEAD (DESIRED) parameter is ON, go to next step. If scan tool does not indicate CONTROL HEAD (DESIRED) parameter is ON, go to step 12 .
  10. Using scan tool, observe PRESSURE STATUS parameter in BCM A/C INFORMATION list. If scan tool indicates PRESSURE STATUS parameter is NORMAL, go to next step. If scan tool does not indicate PRESSURE STATUS parameter is NORMAL, problem is intermittent.
  11. Using scan tool, observe TEMPERATURE STATUS parameter in BCM A/C INFORMATION list. If scan tool indicates TEMPERATURE STATUS parameter is okay, go to step 31 . If scan tool does not indicate TEMPERATURE STATUS parameter is okay, check engine for overheating.
  12. Using scan tool, observe A/C REQUESTED parameter in HVAC SYSTEM data list. Turn mode switch to and from DEFROST position. If scan tool indicates A/C REQUESTED parameter turns on and off with each command, go to step 30 . If scan tool does not indicate A/C REQUESTED parameter turns on and off with each command, go to step 33 .
  13. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 17 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  14. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 27 .
  15. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 29 . If test light does not turn on and off with each command, go to next step.
  16. If test light remains on with each command, go to step 21 . If test light does not remain on with each command, go to step 20 .
  17. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 26 .
  18. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 29 . If A/C compressor clutch does not engage, go to step 22 .
  19. Check ignition voltage circuit (Brown wire) of HVAC control module for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to next step.
  20. Check ground circuit (Black/White wire) of HVAC control module for open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 33 .
  21. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 34 .
  22. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 34 .
  23. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 25 .
  24. Check ground circuit (Black wire) of A/C pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 28 .
  25. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 32 .
  26. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 42 .
  27. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 42 .
  28. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 36 .
  29. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 38 .
  30. Check IPM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 35 .
  31. Check BCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 37 .
  32. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 39 .
  33. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 40 .
  34. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 41 .
  35. Replace IPM. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. After repairs, go to step 42 .
  36. Replace A/C high pressure switch. After repairs, go to step 42 .
  37. Replace BCM. See REMOVAL & INSTALLATION in appropriate BODY CONTROL MODULES article. After repairs, go to step 42 .
  38. Replace A/C compressor clutch relay. After repairs, go to step 42 .
  39. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 42 .
  40. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 42 .
  41. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  42. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S31919908972001042000000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Turn blower motor switch to OFF position. Place A/C switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor clutch does not operate, problem is intermittent.
  3. Using scan tool, observe COMMANDED A/C parameter in PCM data list. If scan tool indicates COMMANDED A/C parameter is ON, go to next step. If scan tool does not indicate COMMANDED A/C parameter is ON, go to step 7 .
  4. Using scan tool, observe A/C CONTROL HEAD (DESIRED) parameter in BCM A/C INFORMATION list. If scan tool displays OFF, go to next step. If scan tool does not display OFF, go to step 12 .
  5. Using scan tool, observe A/C REQUESTED parameter in IPM HVAC SYSTEM data list. If scan tool displays NO, go to next step. If scan tool does not display NO, go to step 13 .
  6. Using scan tool, observe A/C CLUTCH (DESIRED) parameter in BCM A/C INFORMATION list. If scan tool displays OFF, go to step 15 . If scan tool does not display OFF, go to step 14 .
  7. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. If A/C compressor clutch disengages, go to next step. If A/C compressor clutch does not disengage, go to step 9 .
  8. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to step 11 .
  9. Check A/C compressor clutch voltage supply circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to next step.
  10. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to step 17 .
  11. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to step 16 .
  12. Check HVAC connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to step 18 .
  13. Check IPM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to step 19 .
  14. Check BCM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to step 20 .
  15. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 22 . If problem was not found, go to step 21 .
  16. Replace A/C compressor clutch relay. After repairs, go to step 22 .
  17. Replace A/C compressor clutch hub and plate. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 22 .
  18. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 22 .
  19. Replace IPM. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. After repairs, go to step 22 .
  20. Replace BCM. See REMOVAL & INSTALLATION in appropriate BODY CONTROL MODULES article. After repairs, go to step 22 .
  21. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  22. Operate system to verify repair.

3.8L & 5.7L: CAMARO & FIREBIRD

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S28185937752001042300000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place A/C request switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C HIGH SIDE PRESSURE on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 16 .
  5. If HVAC control module is inoperative, go to step 15 . If HVAC control module is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe A/C REQUEST parameter in POWERTRAIN data list. Turn air temperature switch to coldest position. Turn blower motor to ON position. Place A/C request switch in ON position. If scan tool indicates A/C request parameter is YES, go to step 9 . If scan tool does not indicate A/C parameter is YES, go to next step.
  7. If A/C request indicator is on, go to next step. If A/C request indicator is off, go to step 27 .
  8. Turn ignition switch to OFF position. Check A/C request signal circuit (Dark Green/White wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 34 . If problem was not found, go to step 28 .
  9. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 13 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  10. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 22 .
  11. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 23 . If test light does not turn on and off with each command, go to next step.
  12. If test light remains on with each command, go to step 19 . If test light does not remain on with each command, go to step 18 .
  13. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit (Pink wire) of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 23 .
  14. Connect fused jumper (10 amp) between switch side voltage circuit (Pink wire) of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 25 . If A/C compressor clutch does not engage, go to step 20 .
  15. Check voltage supply circuit (Brown wire) to HVAC control assembly for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 34 . If problem was not found, go to step 17 .
  16. Check ground circuit (Gray wire for 3.8L and Purple wire for 5.7L) of A/C pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 34 . If problem was not found, go to step 24 .
  17. Check ground circuit of HVAC control assembly for open. If problem was found, repair as necessary. After repairs, go to step 34 . If problem was not found, go to step 27 .
  18. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 34 . If problem was not found, go to step 28 .
  19. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 34 . If problem was not found, go to step 28 .
  20. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 34 . If problem was not found, go to next step.
  21. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 34 . If problem was not found, go to step 26 .
  22. Repair switch side voltage supply circuit (Pink wire) of A/C compressor clutch relay. After repairs, go to step 34 .
  23. Repair coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. After repairs, go to step 34 .
  24. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 34 . If problem was not found, go to step 29 .
  25. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 34 . If problem was not found, go to step 30 .
  26. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 34 . If problem was not found, go to step 31 .
  27. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 34 . If problem was not found, go to step 32 .
  28. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 34 . If problem was not found, go to step 33 .
  29. Replace A/C high pressure switch. After repairs, go to step 34 .
  30. Replace A/C compressor clutch relay. After repairs, go to step 34 .
  31. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 34 .
  32. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 34 .
  33. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  34. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S28185937752001042300000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Turn blower motor switch to OFF position. Place A/C request switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Using scan tool, observe A/C REQUEST parameter in POWERTRAIN data list. If scan tool indicates A/C REQUEST parameter is YES, go to next step. If scan tool does not indicate A/C REQUEST parameter is YES, go to step 6 .
  4. Check A/C request signal circuit (Dark Green/White wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to next step.
  5. Turn ignition switch to OFF position. Disconnect HVAC control connector. Back out terminal for A/C request circuit (Dark Green/White wire) from HVAC control assembly connector. Reconnect HVAC control assembly connector. Start engine. Using scan tool, observe A/C REQUEST parameter. If scan tool indicates A/C REQUEST parameter is YES, go to step 12 . If scan tool does not indicate A/C REQUEST parameter is YES, go to step 11 .
  6. Turn ignition switch to OFF position. Remove A/C compressor clutch relay. Turn ignition switch to ON position. If A/C compressor clutch turns off, go to next step. If A/C compressor clutch does not turn off, go to step 9 .
  7. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 10 .
  8. Check A/C clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 12 .
  9. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 14 .
  10. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 13 .
  11. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 15 .
  12. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 16 .
  13. Replace A/C compressor clutch relay. After repairs, go to step 17 .
  14. Replace A/C compressor clutch hub and plate assembly. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 17 .
  15. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 17 .
  16. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  17. Operate system to verify repair.

4.6L: DEVILLE & SEVILLE

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

Note. Since many DTCs cause PCM to disable A/C compressor clutch operation, any DTCs stored in memory must be repaired and cleared before proceeding. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S04636847132001042400000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Press A/C switch to ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C HIGH SIDE PRESSURE on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 20 .
  5. If HVAC control module (IPM) is inoperative, go to step 19 . If HVAC control module (IPM) is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe A/C RELAY COMMAND parameter in POWERTRAIN data list. Place air temperature switch in coldest position. Press A/C switch to ON position. If scan tool indicates A/C RELAY COMMAND parameter is ON, go to step 13 . If scan tool does not indicate A/C RELAY COMMAND parameter is ON, go to next step.
  7. Using scan tool, observe A/C CLUTCH (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool indicates A/C CLUTCH (DESIRED) parameter is ON, go to next step. If scan tool does not indicate A/C CLUTCH (DESIRED) parameter is ON, go to step 9 .
  8. Using scan tool, observe A/C CLUTCH (ACTUAL) parameter in DIM A/C INFORMATION list. If scan tool indicates A/C CLUTCH (ACTUAL) parameter is ON, go to step 13 . If scan tool does not indicate A/C CLUTCH (ACTUAL) parameter is ON, go to step 33 .
  9. Using scan tool, observe CONTROL HEAD (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool indicates CONTROL HEAD (DESIRED) parameter is ON, go to next step. If scan tool does not indicate CONTROL HEAD (DESIRED) parameter is ON, go to step 12 .
  10. Using scan tool, observe PRESSURE STATUS parameter in DIM A/C INFORMATION list. If scan tool indicates PRESSURE STATUS parameter is NORMAL, go to next step. If scan tool does not indicate PRESSURE STATUS parameter is NORMAL, problem is intermittent.
  11. Using scan tool, observe TEMPERATURE STATUS parameter in DIM A/C INFORMATION list. If scan tool indicates TEMPERATURE STATUS parameter is okay, go to step 30 . If scan tool does not indicate TEMPERATURE STATUS is okay, check engine for overheating.
  12. Using scan tool, observe CONTROL HEAD (DESIRED) parameter in DIM A/C INFORMATION list. Place mode switch in and out of DEFROST position. If scan tool indicates CONTROL HEAD (DESIRED) parameter turns on and off with each command, go to step 30 . If scan tool does not indicate CONTROL HEAD (DESIRED) parameter turns on and off with each command, go to step 32 .
  13. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 17 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  14. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 27 .
  15. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 29 . If test light does not turn on and off with each command, go to next step.
  16. If test light remain on with each command, go to step 23 . If test light does not remain on with each command, go to step 22 .
  17. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 26 .
  18. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 29 . If A/C compressor clutch does not engage, go to step 24 .
  19. Check ignition voltage circuit (Brown wire) to IPM for a short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 21 .
  20. Check ground circuit (Black wire or Black/White wire) of A/C pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 28 .
  21. Check ground circuit (Black wire) to IPM for open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 32 .
  22. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 33 .
  23. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 33 .
  24. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to next step.
  25. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 31 .
  26. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 40 .
  27. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 40 .
  28. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 35 .
  29. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 36 .
  30. Check DIM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 34 .
  31. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 37 .
  32. Check IPM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 38 .
  33. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 39 .
  34. Replace DIM. See REMOVAL & INSTALLATION in appropriate BODY CONTROL MODULES article. After repairs, go to step 40 .
  35. Replace A/C high pressure switch. After repairs, go to step 40 .
  36. Replace A/C compressor clutch relay. After repairs, go to step 40 .
  37. Replace A/C compressor. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 40 .
  38. Replace IPM. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. After repairs, go to step 40 .
  39. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  40. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S04636847132001042400000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Turn blower motor switch to OFF position. Place A/C switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Using scan tool, observe A/C RELAY COMMAND parameter in POWERTRAIN data list. If scan tool indicates A/C RELAY COMMAND parameter is ON, go to next step. If scan tool does not indicate A/C RELAY COMMAND parameter is ON, go to step 6 .
  4. Using scan tool, observe CONTROL HEAD (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool displays OFF, go to next step. If scan tool does not display OFF, go to step 11 .
  5. Using scan tool, observe A/C CLUTCH (DESIRED) parameter in DIM A/C INFORMATION list. If scan tool displays OFF, go to step 13 . If scan tool does not display OFF, go to step 12 .
  6. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position. If A/C compressor clutch disengages, go to next step. If A/C compressor clutch does not disengage, go to step 8 .
  7. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 10 .
  8. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to next step.
  9. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 15 .
  10. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 14 .
  11. Check IPM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 16 .
  12. Check DIM connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 17 .
  13. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 19 . If problem was not found, go to step 18 .
  14. Replace A/C compressor clutch relay. After repairs, go to step 19 .
  15. Replace A/C compressor. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 19 .
  16. Replace IPM. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. After repairs, go to step 19 .
  17. Replace DIM. See REMOVAL & INSTALLATION in appropriate BODY CONTROL MODULES article. After repairs, go to step 19 .
  18. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  19. Operate system to verify repair.

4.6L: ELDORADO

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

Note. Since many DTCs cause PCM to disable compressor clutch operation, any DTCs stored in memory must be repaired and cleared before proceeding. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S21070433272001042400000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place A/C request switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. If HVAC control module is inoperative, go to step 6 . If HVAC control module is not inoperative, go to next step.
  5. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C OFF SWITCH parameter in CLIMATE CONTROL PANEL (CCP) inputs. Cycle A/C switch on and off. If scan tool parameter turns on and off each time switch is pressed, go to step 8 . If scan tool parameter does not turn on and off each time switch is pressed, go to step 31 .
  6. Check battery voltage circuit (Orange wire) to HVAC control module for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to next step.
  7. Test ground circuit (Black/White wire and Black wire) of HVAC control module for open or high resistance. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 31 .
  8. Turn ignition switch to ON position, with engine off. If A/C system was operating, allow A/C system to equalize for approximately 2 minutes. Using scan tool, observe A/C HIGH and LOW REFRIGERANT PRESSURE SWITCHES in HEATING AND AIR CONDITIONING inputs. If scan tool indicates both HIGH and LOW REFRIGERANT PRESSURE SWITCHES are CLOSED, go to step 12 . If scan tool does not indicate both HIGH and LOW REFRIGERANT PRESSURE SWITCHES are CLOSED, go to next step.
  9. If scan tool indicates high refrigerant pressure switch is open, go to next step. If scan tool does not indicate high refrigerant pressure switch is open, go to step 11 .
  10. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Connect fused jumper (3 amp) across A/C high pressure switch connector. Start engine. Using scan tool, observe HIGH REFRIGERANT PRESSURE SWITCH parameter. If scan tool indicates HIGH REFRIGERANT PRESSURE SWITCH parameter is CLOSED, go to step 33 . If scan tool does not indicate HIGH REFRIGERANT PRESSURE SWITCH parameter is CLOSED, go to step 14 .
  11. Turn ignition switch to OFF position. Disconnect A/C low pressure switch. Connect fused jumper (3 amp) across A/C low pressure switch connector. Start engine. Using scan tool, observe LOW REFRIGERANT PRESSURE SWITCH parameter. If scan tool indicates LOW REFRIGERANT PRESSURE SWITCH parameter is CLOSED, go to step 29 . If scan tool does not indicate LOW REFRIGERANT PRESSURE SWITCH parameter is CLOSED, go to step 15 .
  12. Start engine. Using scan tool, observe A/C POSSIBLE parameter in HEATING AND AIR CONDITIONING inputs. Place A/C in ON position. If scan tool indicates A/C POSSIBLE parameter is ON, go to next step. If scan tool does not indicate A/C POSSIBLE parameter is ON, go to step 32 .
  13. Start engine. Using scan tool, observe COMMANDED A/C parameter in POWERTRAIN data list. Place air temperature switch in coldest position. Place A/C in ON position. If scan tool indicates COMMANDED A/C parameter is ON, go to step 16 . If scan tool does not indicate COMMAND A/C parameter is ON, go to step 34 .
  14. Turn ignition switch to OFF position. Reconnect A/C high pressure switch. Check A/C high pressure switch input circuit (Dark Blue wire) for short to ground, high resistance, or open. If problem is found, repair as necessary. After repairs, go to step 42 . If problem is not found, go to step 34 .
  15. Turn ignition switch to OFF position. Connect A/C low pressure switch. Check A/C low pressure switch input circuit (Dark Green wire) for short to ground, high resistance, or open. If problem is found, repair as necessary. After repairs, go to step 42 . If problem is not found, go to step 34 .
  16. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to next step. If A/C compressor clutch relay does not turn on and off with each command, go to step 19 .
  17. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit (Orange wire) of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 27 .
  18. Connect fused jumper (10 amp) between switch side voltage circuit (Orange wire) of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 28 . If A/C compressor clutch does not engage, go to step 22 .
  19. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit (Dark Blue wire) of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 26 .
  20. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit (Dark Green wire) of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 28 .
  21. If test light remains on with each command, go to step 24 . If test light does not remain on, go to step 25 .
  22. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to next step.
  23. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 30 .
  24. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 34 .
  25. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 34 .
  26. Repair coil side voltage supply circuit (Dark Blue wire) of A/C compressor clutch relay. After repairs, go to step 42 .
  27. Repair switch side voltage supply circuit (Orange wire) of A/C compressor clutch relay. After repairs, go to step 42 .
  28. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 35 .
  29. Check A/C low pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 36 .
  30. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 39 .
  31. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 40 .
  32. Check heater and A/C programmer connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 38 .
  33. Check A/C high pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 37 .
  34. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 42 . If problem was not found, go to step 41 .
  35. Replace A/C compressor clutch relay. After repairs, go to step 42 .
  36. Replace A/C low pressure switch. After repairs, go to step 42 .
  37. Replace A/C high pressure switch. After repairs, go to step 42 .
  38. Replace HVAC control processor. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 42 .
  39. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 42 .
  40. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 42 .
  41. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  42. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S21070433272001042400000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Place A/C switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Using scan tool, observe A/C OFF SWITCH parameter in CLIMATE CONTROL PANEL (CCP). If scan tool indicates A/C OFF SWITCH parameter is OFF, go to next step. If scan tool does not indicate A/C OFF SWITCH parameter is OFF, go to step 12 .
  4. Using scan tool, observe A/C COMMAND parameter in HEATING AND AIR CONDITIONING inputs. If scan tool displays NO, go to next step. If scan tool does not display NO, go to step 13 .
  5. Using scan tool, observe A/C RELAY COMMAND parameter in POWERTRAIN data List 2. If scan tool displays OFF, go to next step. If scan tool does not display OFF, go to step 14 .
  6. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position. If A/C compressor clutch disengages, go to next step. If A/C compressor clutch does not disengage, go to step 9 .
  7. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 11 .
  8. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 14 .
  9. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to next step.
  10. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 16 .
  11. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 15 .
  12. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 17 .
  13. Check HVAC control processor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 18 .
  14. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 20 . If problem was not found, go to step 19 .
  15. Replace A/C compressor clutch relay. After repairs, go to step 20 .
  16. Replace A/C compressor clutch hub and plate. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 20 .
  17. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 20 .
  18. Replace HVAC control processor. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 20 .
  19. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  20. Operate system to verify repair.

5.7L: CORVETTE

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK (AUTOMATIC A/C)»(ref-96385-S20784372812001042500000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place A/C request switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE parameter in POWERTRAIN data list. Compare A/C HIGH SIDE PRESSURE parameter on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 15 .
  5. If HVAC control module is inoperative, go to step 14 . If HVAC control module is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter in POWERTRAIN data list. Place air temperature switch in coldest position. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to next step. If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 26 .
  7. Using scan tool, observe A/C RELAY COMMAND STATUS in POWERTRAIN data list. If scan tool indicates A/C RELAY COMMAND STATUS is ON, go to next step. If scan tool does not indicate A/C RELAY COMMAND STATUS is ON, go to step 27 .
  8. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 12 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  9. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 22 .
  10. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 24 . If test light does not turn on an off with each command, go to next step.
  11. If test light remains on with each command, go to step 18 . If test light does not remain on with each command, go to step 17 .
  12. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 21 .
  13. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 24 . If A/C compressor clutch does not engage, go to step 19 .
  14. Check ignition voltage circuit (Brown wire) of HVAC control module for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 16 .
  15. Check low reference circuit (Black wire) of A/C refrigerant pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 23 .
  16. Check ground circuit (Black wire) of HVAC control module for open. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 26 .
  17. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 27 .
  18. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 27 .
  19. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to next step.
  20. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 25 .
  21. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 33 .
  22. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 33 .
  23. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 28 .
  24. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 29 .
  25. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 30 .
  26. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 31 .
  27. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 33 . If problem was not found, go to step 32 .
  28. Replace A/C refrigerant pressure sensor. After repairs, go to step 33 .
  29. Replace A/C compressor clutch relay. After repairs, go to step 33 .
  30. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 33 .
  31. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 33 .
  32. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  33. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «Diagnostic System Check (Manual A/C)»(ref-96385-S20487169962001042500000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place A/C request switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C HIGH SIDE PRESSURE on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 17 .
  5. If HVAC control module is inoperative, go to step 16 . If HVAC control module is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe A/C REQUEST parameter in POWERTRAIN data list. Place air temperature switch in coldest position. Turn blower motor to ON position. Place A/C REQUEST switch in ON position. If scan tool indicates A/C REQUEST parameter is ON, go to step 10 . If scan tool does not indicate A/C REQUEST parameter is ON, go to next step.
  7. If A/C request indicator is on, go to step 9 . If A/C request indicator is not on, go to next step.
  8. Ensure blower motor switch is in ON position. Turn ignition switch to ON position. Check blower motor off circuit (Light Green wire) at HVAC control module for short to voltage. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 28 .
  9. Turn ignition switch to OFF position. Check A/C request signal circuit (Dark Green/White wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 29 .
  10. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 14 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  11. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 24 .
  12. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 26 . If test light does not turn on and off with each command, go to next step.
  13. If test light remains on with each command, go to step 20 . If test light does not remain on with each command, go to step 19 .
  14. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 23 .
  15. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 26 . If A/C compressor clutch does not engage, go to step 21 .
  16. Check ignition voltage circuit (Brown wire) of HVAC control module for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 18 .
  17. Check ground circuit (Black wire) of A/C refrigerant pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 25 .
  18. Check ground circuit (Black wire) of HVAC control module for open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 28 .
  19. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 29 .
  20. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 29 .
  21. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to next step.
  22. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 27 .
  23. Repair switch side voltage supply circuit of the A/C compressor clutch relay. After repairs, go to step 35 .
  24. Repair coil side voltage supply circuit of the A/C compressor clutch relay. After repairs, go to step 35 .
  25. Check A/C refrigerant pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 30 .
  26. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 31 .
  27. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 32 .
  28. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 33 .
  29. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 34 .
  30. Replace A/C refrigerant pressure sensor. After repairs, go to step 35 .
  31. Replace A/C compressor clutch relay. After repairs, go to step 35 .
  32. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 35 .
  33. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 35 .
  34. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  35. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK (AUTOMATIC A/C)»(ref-96385-S20784372812001042500000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Place blower motor switch in OFF position. Place A/C request switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Using scan tool, observe A/C RELAY COMMAND parameter in POWERTRAIN data list. If scan tool indicates A/C RELAY COMMAND parameter is ON, go to next step. If scan tool does not indicate A/C RELAY COMMAND parameter is ON, go to step 5 .
  4. Using scan tool, observe A/C REQUEST SIGNAL parameter in POWERTRAIN data list. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 10 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 11 .
  5. Remove A/C compressor clutch relay. If A/C compressor clutch turns OFF, go to next step. If A/C compressor clutch does not turn off, go to step 8 .
  6. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 9 .
  7. Check A/C clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 11 .
  8. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 13 .
  9. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 12 .
  10. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 14 .
  11. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 15 .
  12. Replace A/C compressor clutch relay. After repairs, go to step 16 .
  13. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 16 .
  14. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 16 .
  15. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  16. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK (MANUAL A/C)»(ref-96385-S20487169962001042500000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Place blower motor switch in OFF position. Place A/C request switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Using scan tool, observe A/C REQUEST parameter in POWERTRAIN data list. If scan tool indicates A/C REQUEST parameter is ON, go to next step. If scan tool does not indicate A/C REQUEST parameter is ON, go to step 6 .
  4. Check A/C request signal circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to next step.
  5. Turn ignition switch to OFF position. Disconnect HVAC control module connector. Back out terminal for A/C request circuit (Dark Green/White wire) from HVAC control module connector. Reconnect HVAC control module connector. Start engine. Using scan tool, observe A/C REQUEST parameter. If scan tool indicates A/C REQUEST parameter is ON, go to step 12 . If scan tool does not indicate A/C REQUEST parameter in ON, go to step 11 .
  6. Remove A/C compressor clutch relay. If A/C compressor clutch turns off. go to next step. If A/C compressor clutch does not turn off, go to step 9 .
  7. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 10 .
  8. Check A/C clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 12 .
  9. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 14 .
  10. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 13 .
  11. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 15 .
  12. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 16 .
  13. Replace A/C compressor clutch relay. After repairs, go to step 17 .
  14. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 17 .
  15. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 17 .
  16. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  17. Operate system to verify repair.

2.2L: "S" & "T" SERIES

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S08453231462001042700000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place mode switch in bi-level position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C HIGH SIDE PRESSURE on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 18 .
  5. If HVAC control assembly is inoperative, go to step 17 . If HVAC control assembly is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter in POWERTRAIN ENGINE 2 data list. Turn air temperature switch to coldest position. Place mode switch in BI-LEVEL position. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to next step. If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 29 .
  7. Using scan tool, observe A/C REFRIGERANT PRESSURE SENSOR parameter in POWERTRAIN data list. If scan tool indicates A/C HIGH SIDE PRESSURE parameter is 45-425 psi (3.2-29.9 kg/cm 2 ), go to step 11 . If scan tool does not indicate A/C HIGH SIDE PRESSURE parameter is 45-425 psi (3.2-29.9 kg/cm 2 ), go to next step.
  8. Turn ignition switch to OFF position. Disconnect A/C refrigerant pressure sensor. Start engine. Using scan tool, observe A/C HIGH SIDE PRESSURE parameter. If scan tool indicates A/C HIGH SIDE PRESSURE parameter is greater than 425 psi (29.9 kg/cm 2 ), go to next step. If scan tool does not indicate A/C HIGH SIDE PRESSURE parameter is greater than 425 psi (29.9 kg/cm 2 ), go to step 22 .
  9. Turn ignition switch to OFF position. Connect fused jumper (3 amp) between signal circuit (Red/Black wire) and low reference circuit (Black wire) of A/C refrigerant pressure sensor. Start engine. Using scan tool, observe A/C HIGH SIDE PRESSURE parameter. If scan tool indicates A/C REFRIGERANT PRESSURE SENSOR parameter is less than 45 psi (3.2 kg/cm 2 ), go to next step. If scan tool does not indicate A/C REFRIGERANT PRESSURE SENSOR parameter is less than 45 psi (3.2 kg/cm 2 ), go to step 23 .
  10. Turn ignition switch to OFF position. Disconnect fused jumper wire. Connect fused jumper (3 amp) between 5-volt reference circuit (Gray wire) and signal circuit (Red/Black wire) of A/C refrigerant pressure sensor. Start engine. Using scan tool, observe A/C HIGH SIDE PRESSURE parameter. If scan tool indicates A/C REFRIGERANT PRESSURE SENSOR parameter is greater than 425 psi (29.9 kg/cm 2 ), go to step 21 . If scan tool does not indicate A/C REFRIGERANT PRESSURE SENSOR parameter is greater than 425 psi (29.9 kg/cm 2 ), go to step 20 .
  11. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 15 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  12. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C relay. If test light is on, go to next step. If test light is off, go to step 31 .
  13. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 33 . If test light does not turn on and off with each command, go to next step.
  14. If test light remains on with each command, go to step 26 . If test light does not remain on with each command, go to step 25 .
  15. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 30 .
  16. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. If A/C compressor clutch engages, go to step 33 . If A/C compressor clutch does not engage, go to step 27 .
  17. Check ignition voltage circuit (Brown wire) of HVAC control assembly for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 19 .
  18. Check ground circuit (Black wire) of A/C pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 32 .
  19. Check ground circuit of HVAC control assembly for open. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 36 .
  20. Check 5-volt reference circuit (Gray wire) of A/C refrigerant pressure sensor for short to ground. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 37 .
  21. Check 5-volt reference circuit (Gray wire) of A/C refrigerant pressure sensor for short to voltage, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 34 .
  22. Check signal circuit (Red/Black wire) of A/C refrigerant pressure sensor for short to ground. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 37 .
  23. Check signal circuit of A/C refrigerant pressure sensor for short to voltage, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to next step.
  24. Check low reference circuit (Black wire) of A/C refrigerant pressure sensor for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 37 .
  25. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 37 .
  26. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 37 .
  27. Check A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to next step.
  28. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 35 .
  29. Turn ignition switch to OFF position. Check A/C request signal circuit (Light Blue wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 37 .
  30. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 44 .
  31. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 44 .
  32. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 38 .
  33. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 40 .
  34. Check A/C refrigerant pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 39 .
  35. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 41 .
  36. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 42 .
  37. Check PCM/VCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 44 . If problem was not found, go to step 43 .
  38. Replace A/C high pressure switch. After repairs, go to step 44 .
  39. Replace A/C refrigerant pressure sensor. After repairs, go to step 44 .
  40. Replace A/C compressor clutch relay. After repairs, go to step 44 .
  41. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 44 .
  42. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 44 .
  43. Replace PCM/VCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  44. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S08453231462001042700000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Turn blower motor switch to OFF position. Place mode switch in OFF position. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, problem is intermittent.
  3. Using scan tool, observe A/C REQUEST SIGNAL parameter in powertrain data list. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to next step. If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 6 .
  4. Check A/C Request Signal circuit (Light Blue wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to next step.
  5. Turn ignition switch to OFF position. Disconnect PCM harness connector. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter. If scan tool indicates A/C REQUEST parameter is YES, go to step 12 . If scan tool does not indicate A/C REQUEST parameter is YES, go to step 11 .
  6. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to next step. If A/C compressor clutch does not turn off, go to step 9 .
  7. Measure resistance between switch side of A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 10 .
  8. Check A/C compressor clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 12 .
  9. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 14 .
  10. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 13 .
  11. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 15 .
  12. Check PCM/VCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 16 .
  13. Replace A/C compressor clutch relay. After repairs, go to step 17 .
  14. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 17 .
  15. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 17 .
  16. Replace PCM/VCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  17. Operate system to verify repair.

3.4L: "A" & "B" SERIES

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S30245884982001042700000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place A/C request switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C HIGH SIDE PRESSURE on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 23 .
  5. If HVAC control module is inoperative, go to step 18 . If HVAC control module is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter in POWERTRAIN data list. Place air temperature switch in coldest position. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 12 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to next step.
  7. If A/C request indicator is on, go to next step. If A/C request indicator is not on, go to step 32 .
  8. Turn ignition switch to OFF position. Check A/C request signal circuit (Dark Green/White wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to next step.
  9. Disconnect evaporator temperature sensor. Measure resistance of evaporator temperature sensor. See «EVAPORATOR TEMPERATURE SENSOR RESISTANCE»(ref-96385-S16817343352001043000000) table. If resistance is near values specified in sensor resistance table, go to next step. If resistance is not near values specified in sensor resistance table, go to step 30 .
  10. Check evaporator temperature signal circuit (Gray wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to next step.
  11. Check low reference circuit (Black wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 27 .
  12. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 16 . If A/C compressor clutch relay does not turn on and off, go to next step.
  13. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 26 .
  14. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 29 . If test light does not turn on and off with each command, go to next step.
  15. If test light remains on with each command, go to step 21 . If test light does not remain on with each command, go to step 20 .
  16. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 25 .
  17. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 29 . If A/C compressor clutch does not engage, go to step 22 .
  18. Check ignition voltage circuit (Brown wire) of HVAC control module for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to next step.
  19. Check ground circuit (Black wire) of HVAC control module for open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 32 .
  20. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 33 .
  21. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 33 .
  22. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 24 .
  23. Check ground circuit (Black wire) of A/C pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 28 .
  24. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 31 .
  25. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 40 .
  26. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 40 .
  27. Check off blower motor control circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 32 .
  28. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 34 .
  29. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 36 .
  30. Check evaporator temperature sensor for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 35 .
  31. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 37 .
  32. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 38 .
  33. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 39 .
  34. Replace A/C high pressure switch. After repairs, go to step 40 .
  35. Replace evaporator temperature sensor. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 40 .
  36. Replace A/C compressor clutch relay. After repairs, go to step 40 .
  37. Replace the A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 40 .
  38. Replace the HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 40 .
  39. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  40. Operate system to verify repair.
Temp. - °F (°C)Resistance (K/Ohms)
22 (-30)52.8
2 (-20)30.4
14 (-10)18.0
32 (0)11.4
50 (10)7.3
68 (20)4.9
86 (30)3.3
104 (40)2.3
122 (50)1.9

EVAPORATOR TEMPERATURE SENSOR RESISTANCE

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S30245884982001042700000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Turn blower motor switch to OFF position. Place A/C request switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Using scan tool, observe A/C REQUEST SIGNAL parameter in POWERTRAIN data list. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to next step. If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 6 .
  4. Check A/C request signal circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 18 . If problem was not found, go to next step.
  5. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 13 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 12 .
  6. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to next step. If A/C compressor clutch relay does not turn on and off with each command, go to step 9 .
  7. Remove A/C compressor clutch relay. If A/C compressor is on, go to step 10 . If A/C compressor is not on, go to next step.
  8. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance infinite, go to next step. If resistance is not infinite, go to step 11 .
  9. Check A/C clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 18 . If problem was not found, go to step 13 .
  10. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 18 . If problem was not found, go to step 15 .
  11. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 18 . If problem was not found, go to step 14 .
  12. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 18 . If problem was not found, go to step 16 .
  13. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 18 . If problem was not found, go to step 17 .
  14. Replace A/C compressor clutch relay. After repairs, go to step 18 .
  15. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 18 .
  16. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 18 .
  17. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  18. Operate system to verify repair.

3.4L: "U" SERIES (2000)

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S34775427592001043000000) . If diagnostic system check has been performed, go to next step.
  2. Turn ignition switch to OFF position. Install both high and low A/C freon pressure gages. Read freon pressure with engine off. Freon pressure in high and low sides should equal each other after A/C system has come to rest. Freon pressure will fluctuate depending on ambient temperature. Proper clutch operation depends on correct refrigerant charge, low freon charge will shut off A/C compressor operation. If high and low side freon pressures are below 50 psi (3.5 kg/cm 2 ), see LEAK TESTING article in GENERAL SERVICING. If high and low side freon pressures are not below 50 psi (3.5 kg/cm 2 ), go to next step.
  3. If high and low side freon pressures is greater than 100 psi (7.0 kg/cm 2 ), go to next step. If high and low side freon pressures are not greater than 100 psi (7.0 kg/cm 2 ), go to step 5 .
  4. Evacuate and recharge A/C system according to proper freon fill specifications. See appropriate GENERAL SERVICING PROCEDURES articles. After repairs, go to step 23 .
  5. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for a short to ground. If problem was found, repair as necessary. After repairs, go to step 23 . If problem was not found go to next step.
  6. Remove A/C CLU relay from underhood accessory wiring junction block. Disconnect A/C compressor clutch coil connector. Connect fused jumper (10 amp) between ignition feed terminal for switch side of A/C CLU relay and A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C CLU relay. Connect DVOM between A/C compressor clutch coil connector terminal "B" (Dark Green wire) and ground. Turn ignition switch to ON position. Measure available voltage at A/C compressor clutch coil connector terminal "B". If battery voltage is present, go to step 8 . If battery voltage is not present, go to next step.
  7. Repair poor connection or open in A/C compressor voltage supply circuit (Dark Green wire). After repairs, go to step 23 .
  8. Using DVOM, measure resistance between terminal "A" (Black wire) of A/C compressor clutch coil connector and ground. If resistance is 0-2 ohms, go to step 10 . If resistance is not 0-2 ohms, go to next step.
  9. Repair poor connection or open in A/C compressor clutch ground circuit (Black wire). After repairs, go to step 23 .
  10. Disconnect PCM connector C2. Reinstall A/C CLU relay. Connect fused jumper (10 amp) between A/C CLU relay control circuit (Dark Green/White wire) at PCM connector C2 and ground. Turn ignition switch to ON position. Using DVOM, measure voltage between A/C compressor clutch voltage supply circuit (Dark Green wire) and ground. If battery voltage is present, go to next step. If battery voltage is not present, go to step 12 .
  11. Remove fused jumper between PCM connector C2 and ground. Reconnect A/C compressor clutch coil connector. Reinstall fused jumper between A/C CLU relay control circuit (Dark Green/White wire) at PCM connector C2 and ground. Turn ignition on. If A/C compressor clutch engages, see TESTING under appropriate MANUAL A/C-HEATER SYSTEMS article. If A/C compressor clutch does not engage, go to step 22 .
  12. Turn ignition switch to OFF position. Remove A/C CLU relay. Using DVOM, measure resistance of Dark Green/White wire between PCM connector C2 and underhood accessory wiring junction block connector C1. If resistance is 0-2 ohms, go to step 14 . If resistance is not 0-2 ohms, go to next step.
  13. Repair poor connection or open in Dark Green/White wire between PCM connector C2 and underhood accessory wiring junction block connector C1. After repairs, go to step 23 .
  14. Replace A/C CLU relay and retest A/C system. If problem has been corrected, go to step 23 . If problem has not been corrected, go to next step.
  15. Disconnect A/C-heater control connector C2. Using DVOM, measure resistance in Dark Green/White wire between PCM connector C2 and A/C-heater control connector C2. If resistance is 0-2 ohms, go to step 17 . If resistance is not 0-2 ohms, go to next step.
  16. Repair poor connection or open in Dark Green/White wire between PCM connector C2 and A/C-heater control connector C2. After repairs, go to step 23 .
  17. Using DVOM, check continuity between Dark Green/White wire at PCM connector C2 and ground. If continuity exists, go to next step. If continuity does not exist, go to step 19 .
  18. Repair short to ground in Dark Green/White wire between Dark Green/White wire at PCM connector C2 and ground. After repairs, go to step 23 .
  19. Disconnect DVOM. Reconnect all connectors back to their respective modules. Install scan tool to diagnostic link connector. Start engine and allow to idle in park. Select area of scan tool which will read HVAC button output status. Depress A/C button on and off several times. If scan tool reads A/C REQUEST being sent by HVAC control head, go to next step. If scan tool does not read A/C REQUEST being sent by HVAC control head, go to step 21 .
  20. Check PCM and underhood accessory wiring junction block connectors for poor connections. If problem was found, repair as necessary. If problem was not found, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to step 23 .
  21. Replace A/C-heater control. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 23 .
  22. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to next step.
  23. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S34775427592001043000000) . If diagnostic system check has been performed, go to next step.
  2. Disconnect PCM connector C2. Turn ignition switch to ON position. If A/C compressor clutch disengages, go to next step. If A/C compressor clutch does not disengage, go to step 4 .
  3. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to step 11 .
  4. Disconnect A/C CLU relay from underhood accessory wiring junction block. Turn ignition switch to ON position. If A/C compressor clutch disengages, go to next step. If A/C compressor clutch does not disengage, go to step 8 .
  5. Turn ignition switch to OFF position. Using DVOM, check continuity between PCM connector C2 terminal No. 39 (Dark Green/White wire) and ground. If continuity exists, go to next step. If continuity does not exist, go to step 7 .
  6. Repair short to ground in Dark Green/White wire between underhood accessory wiring junction block and PCM connector. After repairs, go to step 11 .
  7. Replace A/C CLU relay. After repairs, go to step 11 .
  8. Disconnect A/C compressor clutch coil connector. Using DVOM, measure voltage between A/C compressor clutch coil connector terminal "B" (Dark Green wire) and ground. Turn ignition switch to ON position. If battery voltage is present, go to next step. If battery voltage is not present, go to step 10 .
  9. Repair short to battery voltage in Dark Green wire between underhood accessory wiring junction block and A/C compressor clutch coil. After repairs, go to step 11 .
  10. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to next step.
  11. Turn ignition switch to OFF position. Reconnect all connectors/components disconnected. Operate system to verify repair.

3.4L: "U" SERIES (2001)

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S18130907662001043000000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place A/C request switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C HIGH SIDE PRESSURE on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 20 .
  5. If HVAC control assembly is inoperative, go to step 19 . If HVAC control assembly is not inoperative, go to next step.
  6. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter in POWERTRAIN engine data list. Place air temperature switch in coldest position. Turn blower motor to on position. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST parameter is YES, go to step 13 . If scan tool does not indicate A/C REQUEST parameter is YES, go to next step.
  7. If A/C request indicator is on, go to step 9 . If A/C request indicator is not on, go to next step.
  8. Ensure blower motor is in ON position. Turn ignition switch to ON position. Check OFF blower motor control circuit (Dark Green wire) at HVAC control module for short to voltage. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 32 .
  9. Turn ignition switch to OFF position. Check A/C request signal circuit (Dark Green/White wire) for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to next step.
  10. Disconnect evaporator temperature sensor. Measure resistance of evaporator temperature sensor. See «EVAPORATOR TEMPERATURE SENSOR RESISTANCE»(ref-96385-S16817343352001043000000) table under 3.4L: "A" & "B" SERIES. If resistance measures near value specified in sensor resistance table, go to next step. If resistance does not measure near value specified in sensor resistance table, go to step 30 .
  11. Check evaporator temperature sensor signal circuit (White wire) for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to next step.
  12. Check evaporator temperature sensor low reference circuit (Black wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem was not found, go to step 32 .
  13. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 17 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  14. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 27 .
  15. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 27 . If test light does not turn on and off with each command, go to next step.
  16. If test light remains on with each command, go to step 23 . If test light does not remain on with each command, go to step 22 .
  17. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 26 .
  18. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 29 . If A/C compressor clutch does not engage, go to step 24 .
  19. Check voltage supply circuits (Brown wires and Orange wire) to HVAC control assembly for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem is not found, go to step 21 .
  20. Check ground circuit (Black wire) of A/C pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem is not found, go to step 28 .
  21. Check ground circuit (Black wire) of HVAC control assembly for open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem is not found, go to step 32 .
  22. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem is not found, go to step 33 .
  23. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 40 . If problem is not found, go to step 33 .
  24. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem is not found, go to next step.
  25. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 40 . If problem is not found, go to step 31 .
  26. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 40 .
  27. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 40 .
  28. Check A/C high pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem is not found, go to step 34 .
  29. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem is not found, go to step 36 .
  30. Check evaporator temperature sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem is not found, go to step 35 .
  31. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem is not found, go to step 37 .
  32. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem is not found, go to step 38 .
  33. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 40 . If problem is not found, go to step 39 .
  34. Replace A/C high pressure switch. After repairs, go to step 40 .
  35. Replace evaporator temperature sensor. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 40 .
  36. Replace A/C compressor clutch relay. After repairs, go to step 40 .
  37. Replace A/C compressor. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 40 .
  38. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 40 .
  39. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  40. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S18130907662001043000000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Place blower motor switch in OFF position. Place A/C request switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Using scan tool, observe A/C REQUEST SIGNAL parameter in POWERTRAIN ENGINE data list. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to next step. If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 6 .
  4. Check A/C request signal circuit (Dark Green/White wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to next step.
  5. Turn ignition switch to OFF position. Disconnect HVAC control module connector. Back out terminal for A/C request signal circuit (Dark Green/White wire) from HVAC control head. Reconnect HVAC control module connector. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 12 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 11 .
  6. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to next step. If A/C compressor clutch does not turn off, go to step 9 .
  7. Measure resistance between switch side of A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 10 .
  8. Check A/C compressor clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 12 .
  9. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 14 .
  10. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 13 .
  11. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 15 .
  12. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 16 .
  13. Replace A/C compressor clutch relay. After repairs, go to step 17 .
  14. Replace A/C compressor. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 17 .
  15. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 17 .
  16. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  17. Operate system to verify repair.

4.3L: "M" & "L" SERIES

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

Note. HVAC control assembly may be referred to as HVAC control module. 2000 vehicles use a Vehicle Control Module (VCM) and 2001 vehicles use a Powertrain Control Module (PCM).

  1. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place mode switch in bi-level position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  2. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  3. If HVAC control assembly is inoperative, go to step 17 . If HVAC control assembly is not inoperative, go to next step.
  4. Start engine. Using scan tool, observe A/C REQUEST parameter. Place air temperature switch in coldest position. Place mode switch in bi-level position. If scan tool indicates A/C REQUEST parameter is ON, go to step 6 . If scan tool does not indicate A/C REQUEST parameter is ON, go to next step.
  5. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Connect fused jumper (3 amp) between A/C request circuits (Light Orange wire and Dark Green/White wire) at A/C high pressure switch connector. Start engine. Using scan tool, observe A/C REQUEST parameter. Place air temperature switch in coldest position. Place mode switch in bi-level position. If scan tool indicated A/C request parameter is ON, go to step 29 . If scan tool does not indicate A/C REQUEST parameter is ON, go to step 23 .
  6. If scan tool indicates A/C LOW PRESSURE SWITCH parameter is CLOSED, go to step 8 . If scan tool does not indicate A/C LOW PRESSURE SWITCH parameter is CLOSED, go to next step.
  7. Turn ignition switch to OFF position. Disconnect A/C low pressure switch. Connect fused jumper (3 amp) between A/C low pressure switch signal circuit (Dark Green wire) and ground circuit (Black wire) at A/C low pressure switch connector. Start engine. Using scan tool, observe A/C LOW PRESSURE SWITCH parameter. If scan tool indicates A/C LOW PRESSURE SWITCH parameter is CLOSED, go to step 26 . If scan tool does not indicate A/C LOW PRESSURE SWITCH is CLOSED, go to step 19 .
  8. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turn on and off with each command, go to step 14 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  9. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 24 .
  10. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 25 . If test light does not turn on and off with each command, go to next step.
  11. If test light remains on with each command, go to step 13 . If test light does not remain on with each command, go to next step.
  12. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to step 30 .
  13. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to step 30 .
  14. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit (Orange wire) of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 16 .
  15. Connect fused jumper (10 amp) between switch side voltage circuit (Orange wire) of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 25 . If A/C compressor clutch does not engage, go to step 21 .
  16. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 37 .
  17. Check ignition voltage circuit (Brown wire) of HVAC control assembly for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to next step.
  18. Check ground circuit (Black wire) of HVAC control assembly for open. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to step 28 .
  19. Check A/C low pressure switch signal circuit (Dark Green wire) for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to step 20 .
  20. Check ground circuit (Black wire) of A/C low pressure switch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to step 30 .
  21. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to next step.
  22. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to step 27 .
  23. Turn ignition switch to OFF position. Reconnect A/C high pressure switch. Check A/C request signal circuit (Light Green wire and Dark Green/White wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to step 30 .
  24. Repair coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. After repairs, go to step 37 .
  25. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to step 31 .
  26. Check A/C low pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to step 32 .
  27. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to step 34 . at the harness connector of the A/C compressor clutch.
  28. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to step 35 .
  29. Check A/C high pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to step 33 .
  30. Check PCM/VCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 37 . If problem was not found, go to step 36 .
  31. Replace A/C compressor clutch relay. After repairs, go to step 37 .
  32. Replace A/C low pressure switch. After repairs, go to step 37 .
  33. Replace A/C high pressure switch. After repairs, go to step 37 .
  34. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 37 .
  35. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 37 .
  36. Replace PCM/VCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  37. Operate system to verify repair.
  1. Start engine. Place blower motor switch in OFF position. Place mode switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  2. Using scan tool, observe A/C REQUEST parameter in POWERTRAIN data list. If scan tool indicates A/C REQUEST parameter is ON, go to next step. If scan tool does not indicate A/C REQUEST parameter in ON, go to step 5 .
  3. Check A/C request signal circuit (Light Green wire and Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to next step.
  4. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Start engine. Using scan tool, observe A/C REQUEST parameter. If scan tool indicates A/C REQUEST parameter is ON, go to step 11 . If scan tool does not indicate A/C REQUEST parameter is ON, go to step 10 .
  5. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to next step. If A/C compressor clutch does not turn off, go to step 8 .
  6. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 9 .
  7. Check A/C clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 11 .
  8. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 13 .
  9. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 12 .
  10. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 14 .
  11. Check PCM/VCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 15 .
  12. Replace A/C compressor clutch relay. After repairs, go to step 16 .
  13. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 16 .
  14. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 16 .
  15. Replace PCM/VCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  16. Operate system to verify repair.

4.3L: "S" & "T" SERIES (AUTOMATIC A/C)

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S41414288802001050100000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place mode switch in bi-level position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. If HVAC control module is inoperative, go to step 17 . If HVAC control module is not inoperative, go to next step.
  5. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter in POWERTRAIN ENGINE 2 data list. Place air temperature switch in coldest position. Place mode switch in bi-level position. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 7 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to next step.
  6. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Connect fused jumper (3 amp) between A/C Request Signal circuits (Light Blue wire and Dark Green/White wire) at A/C high pressure switch connector. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter. Place air temperature switch in coldest position. Place mode switch in bi-level position. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 31 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 23 .
  7. Turn engine off. Ensure ignition is in ON position. If scan tool indicates A/C COMPRESSOR CYCLING SWITCH parameter reads LOW PRESSURE, go to step 9 . If scan tool does not indicate A/C COMPRESSOR CYCLING SWITCH parameter reads LOW PRESSURE, go to next step.
  8. Turn ignition switch to OFF position. Disconnect A/C low pressure switch. Connect fused jumper (3 amp) between A/C low pressure switch signal circuit (Dark Green wire) and ground circuit (Black/White wire) at A/C low pressure switch connector. Start engine. Using scan tool, observe A/C COMPRESSOR CYCLING SWITCH parameter. If scan tool indicates A/C COMPRESSOR CYCLING SWITCH parameter reads LOW PRESSURE, go to step 28 . If scan tool does not indicate A/C COMPRESSOR CYCLING SWITCH parameter reads LOW PRESSURE, go to step 19 .
  9. Using scan tool, command A/C relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 13 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  10. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 26 .
  11. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C Relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 27 . If test light does not turn on and off with each command, go to next step.
  12. If test light remains on with each command, go to step 16 . If test light does not remain on with each command, go to step 15 .
  13. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 25 .
  14. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. If A/C compressor clutch engages, go to step 27 . If A/C compressor clutch does not engage, go to step 21 .
  15. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open or short to voltage. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 32 .
  16. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 32 .
  17. Check ignition voltage circuit (Brown wire) of HVAC control assembly for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to next step.
  18. Check ground circuit (Black wire) of HVAC control assembly for open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 30 .
  19. Check A/C low pressure switch signal circuit (Dark Green wire) for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to next step.
  20. Check ground circuit (Black/White wire) of A/C low pressure switch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 32 .
  21. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to next step.
  22. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 29 .
  23. Turn ignition switch to OFF position. Reconnect A/C high pressure switch. Check A/C request signal circuit (Light Green wire and Dark Green/White wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to next step.
  24. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Turn ignition switch to ON position. Place mode switch in bi-level position. Using test light connected to ground, probe A/C request signal circuit (Light Blue wire) of A/C high pressure switch. If test light is on, go to step 32 . If test light is off, go to step 30 .
  25. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 39 .
  26. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 39 .
  27. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 33 .
  28. Check A/C low pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 34 .
  29. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 36 .
  30. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 37 .
  31. Check A/C high pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 35 .
  32. Check PCM/VCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 38 .
  33. Replace A/C compressor clutch relay. After repairs, go to step 39 .
  34. Replace A/C low pressure switch. After repairs, go to step 39 .
  35. Replace A/C high pressure switch. After repairs, go to step 39 .
  36. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 39 .
  37. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 39 .
  38. Replace PCM/VCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  39. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S41414288802001050100000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Place blower motor switch in OFF position. Place A/C request switch in OFF position. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, problem is intermittent.
  3. Using scan tool, observe A/C REQUEST parameter in POWERTRAIN data list. If scan tool indicates A/C REQUEST parameter is ON, go to next step. If scan tool does not indicate A/C REQUEST parameter is ON, go to step 6 .
  4. Check A/C request signal circuit (Light Blue wire and Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to next step.
  5. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Start engine. Using scan tool, observe A/C REQUEST parameter. If scan tool indicates A/C REQUEST parameter is ON, go to step 12 . If scan tool does not indicate A/C REQUEST parameter is ON, go to step 11 .
  6. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to next step. If A/C compressor clutch does not turn off, go to step 9 .
  7. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 10 .
  8. Check A/C clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 12 .
  9. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 14 .
  10. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 13 .
  11. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 15 .
  12. Check PCM/VCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 16 .
  13. Replace A/C compressor clutch relay. After repairs, go to step 17 .
  14. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 17 .
  15. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 17 .
  16. Replace PCM/VCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  17. Operate system to verify repair.

4.3L: "S" & "T" SERIES (MANUAL A/C)

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S00719371192001050200000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 38°F (3°C). Start engine. Turn blower motor switch to maximum speed position. Place mode switch in bi-level position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. If HVAC control module is inoperative, go to step 17 . If HVAC control module is not inoperative, go to next step.
  5. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter in POWERTRAIN ENGINE 2 data list. Place air temperature switch in coldest position. Place mode switch in bi-level position. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 7 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to next step.
  6. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Connect fused jumper (3 amp) between A/C Request Signal circuits (Light Blue wire and Dark Green/White wire) at A/C high pressure switch connector. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter. Place air temperature switch in coldest position. Place mode switch in bi-level position. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 31 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 23 .
  7. Turn engine off. Ensure ignition is in ON position. If scan tool indicates A/C COMPRESSOR CYCLING SWITCH parameter reads LOW PRESSURE, go to step 9 . If scan tool does not indicate A/C COMPRESSOR CYCLING SWITCH parameter reads LOW PRESSURE, go to next step.
  8. Turn ignition switch to OFF position. Disconnect A/C low pressure switch. Connect fused jumper (3 amp) between A/C low pressure switch signal circuit (Dark Green wire) and ground circuit (Black/White wire) at A/C low pressure switch connector. Start engine. Using scan tool, observe A/C COMPRESSOR CYCLING SWITCH parameter. If scan tool indicates A/C COMPRESSOR CYCLING SWITCH parameter reads LOW PRESSURE, go to step 28 . If scan tool does not indicate A/C COMPRESSOR CYCLING SWITCH parameter reads LOW PRESSURE, go to step 19 .
  9. Using scan tool, command A/C relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 13 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  10. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 26 .
  11. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C Relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 27 . If test light does not turn on and off with each command, go to next step.
  12. If test light remains on with each command, go to step 16 . If test light does not remain on with each command, go to step 15 .
  13. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 25 .
  14. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. If A/C compressor clutch engages, go to step 27 . If A/C compressor clutch does not engage, go to step 21 .
  15. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open or short to voltage. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 32 .
  16. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 32 .
  17. Check ignition voltage circuit (Brown wire) of HVAC control assembly for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to next step.
  18. Check ground circuit (Black wire) of HVAC control assembly for open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 30 .
  19. Check A/C low pressure switch signal circuit (Dark Green wire) for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to next step.
  20. Check ground circuit (Black/White wire) of A/C low pressure switch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 32 .
  21. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to next step.
  22. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 29 .
  23. Turn ignition switch to OFF position. Reconnect A/C high pressure switch. Check A/C request signal circuit (Light Green wire and Dark Green/White wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to next step.
  24. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Turn ignition switch to ON position. Place mode switch in bi-level position. Using test light connected to ground, probe A/C request signal circuit (Light Blue wire) of A/C high pressure switch. If test light is on, go to step 32 . If test light is off, go to step 30 .
  25. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 39 .
  26. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 39 .
  27. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 33 .
  28. Check A/C low pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 34 .
  29. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 36 .
  30. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 37 .
  31. Check A/C high pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 35 .
  32. Check PCM/VCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 38 .
  33. Replace A/C compressor clutch relay. After repairs, go to step 39 .
  34. Replace A/C low pressure switch. After repairs, go to step 39 .
  35. Replace A/C high pressure switch. After repairs, go to step 39 .
  36. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 39 .
  37. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 39 .
  38. Replace PCM/VCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  39. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S00719371192001050200000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Place blower motor switch in OFF position. Place mode switch in OFF position. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, problem is intermittent.
  3. Using scan tool, observe A/C REQUEST SIGNAL parameter in POWERTRAIN data list. If scan tool indicates A/C REQUEST SIGNAL parameter is ON, go to next step. If scan tool does not indicate A/C REQUEST SIGNAL parameter is ON, go to step 6 .
  4. Check A/C request signal circuit (Light Blue wire and Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to next step.
  5. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter. If scan tool indicates A/C REQUEST SIGNAL parameter is ON, go to step 12 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is ON, go to step 11 .
  6. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to next step. If A/C compressor clutch does not turn off, go to step 9 .
  7. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 10 .
  8. Check A/C clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 12 .
  9. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 14 .
  10. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 13 .
  11. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 15 .
  12. Check PCM/VCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 16 .
  13. Replace A/C compressor clutch relay. After repairs, go to step 17 .
  14. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 17 .
  15. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate AUTOMATIC A/C-HEATER SYSTEMS article. After repairs, go to step 17 .
  16. Replace PCM/VCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  17. Operate system to verify repair.

4.3L & 7.4L: "C" & "K" SERIES (2000) OR 4.3L, 5.0L & 5.7L: "G" SERIES (2000)

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

4.8L, 5.3L & 6.0L: "C" & "K" SERIES (2000)

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

5.0L & 5.7L: "C" & "K" SERIES (2000) OR 7.4L: "G" SERIES (2000)

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

6.5L: "C" & "K" SERIES (2000)

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

HVAC Compressor Controls System Check

  1. Start vehicle. Turn blower switch to HIGH position. Turn A/C on. A/C compressor clutch engages. If cold air comes from air vents, system is okay. If air from vents does not get cold, see «COMPRESSOR CLUTCH DOES NOT ENGAGE»(ref-96385-S37688283572001050400000) .
  2. Turn A/C off, leave blower on high. A/C compressor clutch should disengage. If cool air from vents turns warm after a few minutes, system is okay. If air remains cool coming from vents, see «COMPRESSOR CLUTCH DOES NOT DISENGAGE»(ref-96385-S09270235172001050400000) .
  1. Ensure A/C system has sufficient refrigerant charge. If refrigerant charge is sufficient, go to next step. If refrigerant charge is not sufficient, see CHARGING A/C SYSTEM in GENERAL SERVICING PROCEDURES article.
  2. Disconnect PCM connector C3. Connect fused jumper wire between VCM connector C3 terminal D5 (Dark Green/White wire) and ground. Turn ignition switch to ON position. If audible click from A/C compressor clutch is heard, go to step 14 . If audible click from A/C compressor clutch is not heard, go to next step.
  3. Remove A/C compressor clutch relay. Connect fused jumper wire between A/C compressor clutch relay connector terminals B4 (Orange wire) and A6 (Dark Green wire). If clutch engages, go to next step. If clutch does not engage, go to step 7 .
  4. Disconnect PCM connector C3. Connect fused jumper wire between A/C compressor clutch relay terminals A4 (Pink wire) and B6 (Dark Green/White wire). Using DVOM, measure voltage between PCM connector C3 terminal D5 (Dark Green/White wire) and ground. Turn ignition switch to ON position. If battery voltage is present, go to next step. If battery voltage is not present, go to step 6 .
  5. Replace A/C compressor clutch relay. After repairs, recheck system operation.
  6. Repair open in Dark Green wire between underhood fuse block and PCM. After repairs, recheck system operation.
  7. Disconnect A/C compressor clutch connector. Using DVOM, check continuity between A/C compressor clutch connector terminal "A" (Black wire) and ground. If continuity exists, go to step 9 . If continuity does not exist, go to next step.
  8. Repair open in Black wire between compressor clutch and ground. After repairs, recheck system operation.
  9. Connect fused jumper wire between A/C compressor clutch relay connector terminals B4 (Orange wire) and A6 (Dark Green wire). Using DVOM, measure voltage between terminals of compressor clutch connector. If battery voltage is present, go to step 11 . If battery voltage is not present, go to next step.
  10. Repair open in Dark Green wire between underhood fuse block and compressor clutch connector. After repairs, recheck system operation.
  11. Remove fused jumper wire between at A/C compressor clutch relay connector. Using DVOM, check continuity between compressor clutch connector terminals. Reverse meter leads at connector and check continuity again. If continuity is present in one direction only, go to step 13 . If continuity is not present in one direction only, go to next step.
  12. Replace diode located within A/C compressor clutch harness. After repairs, recheck system operation.
  13. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, recheck system operation.
  14. Disconnect A/C compressor cycling switch. Connect jumper between A/C compressor cycling switch connector terminals. Using DVOM, measure voltage between PCM connector C1 terminal C2 (Dark Green wire) and ground. Turn ignition switch to ON position. Turn front blower switch to any position except OFF. Push in A/C Button. If battery voltage is present, go to next step. If battery voltage is not present, go to step 16 .
  15. Replace A/C compressor cycling switch. After repairs, recheck system operation.
  16. Disconnect A/C high pressure switch connector. Connect fused jumper wire between A/C high pressure switch connectors. Using DVOM, measure voltage between PCM connector C1 terminal C2 (Dark Green wire) and ground. Turn ignition switch to ON position. Turn front blower switch to any position except OFF. Push in A/C Button. If battery voltage is present, go to next step. If battery voltage is not present, go to step 18 .
  17. Replace A/C high pressure switch. After repairs, recheck system operation.
  18. Disconnect HVAC control module connector C3. Connect fused jumper between HVAC control module connector C3 terminals No. 5 (Brown wire) and No. 10 (Light Green wire). Using DVOM, measure voltage between PCM connector C1 terminal C2 (Dark Green/White) and ground. Turn ignition switch to ON position. Turn front blower switch to any position except OFF. Push in A/C Button. If battery voltage is present, go to next step. If battery voltage is not present, go to step 20 .
  19. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, recheck system operation.
  20. Repair open in Brown wire, Light Green wire, Dark Green wire or Dark Green/White wire between instrument panel fuse block and PCM. After repairs, recheck system operation.
  1. If HVAC compressor controls system check has been performed, go to next step. If HVAC compressor controls system check has not been performed, see «HVAC COMPRESSOR CONTROLS SYSTEM CHECK»(ref-96385-S11401480762001050400000) .
  2. Turn ignition switch to ON position. Remove A/C Compressor Clutch Relay. If A/C compressor clutch disengages, go to step 6 . If A/C compressor clutch does not disengage, go to next step.
  3. Using DVOM, measure voltage between A/C compressor clutch relay connector terminal A6 (Dark Green wire) and ground. If voltage is greater than 0.5 volt, go to next step. If voltage is not greater than 0.5 volts, go to step 5 .
  4. Repair short to battery voltage in Dark Green wire between A/C compressor clutch relay and A/C compressor clutch. After repairs, perform «HVAC COMPRESSOR CONTROLS SYSTEM CHECK»(ref-96385-S11401480762001050400000) .
  5. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, perform «HVAC COMPRESSOR CONTROLS SYSTEM CHECK»(ref-96385-S11401480762001050400000) .
  6. Connect fused jumper between A/C compressor clutch relay connector terminal A4 (Pink wire) and battery voltage. Connect second jumper between A/C compressor clutch relay connector terminal B6 (Dark Green/White wire) and ground. If relay clicks, go to step 8 .
  7. Replace A/C Compressor Clutch Relay. After repairs, perform «HVAC COMPRESSOR CONTROLS SYSTEM CHECK»(ref-96385-S11401480762001050400000) .
  8. Turn ignition switch to OFF position. Using DVOM, measure continuity between A/C compressor clutch relay connector terminal B6 (Dark Green/White wire) and ground. If continuity is present, go to next step. If continuity does not exist, go to step 10 .
  9. Repair short to ground in Dark Green/White wire between A/C compressor clutch relay and PCM. After repairs, perform «HVAC COMPRESSOR CONTROLS SYSTEM CHECK»(ref-96385-S11401480762001050400000) .
  10. Turn ignition switch to ON position. Disconnect HVAC Control Module connector C3. Using DVOM, measure voltage between PCM connector C1 terminal C2 (Dark Green/White wire) and ground. If battery voltage is present, go to step 12 . If battery voltage is not present, go to next step.
  11. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, perform «HVAC COMPRESSOR CONTROLS SYSTEM CHECK»(ref-96385-S11401480762001050400000) .
  12. Repair short to battery voltage in Light Green wire, Dark Green wire or Dark Green/White wire between HVAC control module and PCM. After repairs, perform «HVAC COMPRESSOR CONTROLS SYSTEM CHECK»(ref-96385-S11401480762001050400000) .

4.3L, 4.8L, 5.3L, 6.0L, 6.6L & 8.1L: "C" & "K" SERIES (AUTOMATIC A/C 2001)

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S31424817212001050400000) . If diagnostic system check has been performed, go to next step.
  2. Ensure outside air temperature is greater than 40°F (4°C). Start engine. Turn blower motor switch to maximum speed position. Place A/C switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  4. If HVAC control module is inoperative, go to step 19 . If HVAC control module is not inoperative, go to next step.
  5. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 8 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to next step.
  6. If A/C request indicator is on, go to next step. If A/C request indicator is not on, go to step 30 .
  7. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Connect fused jumper (3 amp) between A/C high pressure switch connector terminals. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 31 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 25 .
  8. If scan tool indicates A/C COMPRESSOR CYCLING SWITCH parameter is NORMAL, go to step 10 . If scan tool does not indicate A/C COMPRESSOR CYCLING SWITCH parameter is NORMAL, go to next step.
  9. Turn ignition switch to OFF position. Disconnect A/C low pressure switch. Connect fused jumper (3 amp) between A/C low pressure switch connector terminals. Start engine. Using scan tool, observe A/C COMPRESSOR CYCLING SWITCH parameter. If scan tool indicates A/C COMPRESSOR CYCLING SWITCH parameter is NORMAL, go to step 28 . If scan tool does not indicate A/C COMPRESSOR CYCLING SWITCH parameter is NORMAL, go to step 21 .
  10. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 16 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  11. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 26 .
  12. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 27 . If test light does not turn on and off with each command, go to next step.
  13. If test light remains on with each command, go to step 15 . If test light does not remain on with each command, go to next step.
  14. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 32 .
  15. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 32 .
  16. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 18 .
  17. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 27 . If A/C compressor clutch does not engage, go to step 23 .
  18. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 39 .
  19. Check ignition voltage circuit (Brown wire) of HVAC control module for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to next step.
  20. Check ground circuit (Black wire) of HVAC control module for open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 30 .
  21. Check A/C low pressure switch signal circuit (Dark Green wire) for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to next step.
  22. Check ground circuit (Black wire) of A/C low pressure switch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 32 .
  23. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to next step.
  24. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 29 .
  25. Turn ignition switch to OFF position. Reconnect A/C high pressure switch. Check A/C request signal circuit (Light Blue wire and Dark Green/White wire) for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 32 .
  26. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 39 .
  27. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 33 .
  28. Check A/C low pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 34 .
  29. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 36 .
  30. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 37 .
  31. Check A/C high pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 35 .
  32. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 38 .
  33. Replace A/C compressor clutch relay. After repairs, go to step 39 .
  34. Replace A/C low pressure switch. After repairs, go to step 39 .
  35. Replace A/C high pressure switch. After repairs, go to step 39 .
  36. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 39 .
  37. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 39 .
  38. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  39. Operate system to verify repair.
  1. If diagnostic system check has not been performed, see «DIAGNOSTIC SYSTEM CHECK»(ref-96385-S31424817212001050400000) . If diagnostic system check has been performed, go to next step.
  2. Start engine. Place blower motor switch in OFF position. Place A/C request switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  3. Using scan tool, observe A/C REQUEST SIGNAL parameter in POWERTRAIN data list. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to next step. If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 6 .
  4. Check A/C request signal circuit (Light Blue wire and Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to next step.
  5. Turn ignition switch to off position. Disconnect A/C high pressure switch. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 12 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 11 .
  6. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to next step. If A/C compressor clutch does not turn off, go to step 9 .
  7. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 10 .
  8. Check A/C compressor clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 12 .
  9. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 14 .
  10. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 13 .
  11. Check HVAC control module for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 15 .
  12. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 17 . If problem was not found, go to step 16 .
  13. Replace A/C compressor clutch relay. After repairs, go to step 17 .
  14. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 17 .
  15. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 17 .
  16. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  17. Operate system to verify repair.

4.3L, 4.8L, 5.3L, 6.0L, 6.6L & 8.1L: "C" & "K" SERIES (MANUAL A/C 2001)

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

  1. Ensure outside air temperature is greater than 40°F (4°C). Start engine. Turn blower motor switch to maximum speed position. Place A/C switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  2. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  3. If HVAC control module is inoperative, go to step 18 . If HVAC control module is not inoperative, go to next step.
  4. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 7 . If scan tool does not indicate A/C REQUEST parameter is YES, go to next step.
  5. If A/C request indicator is on, go to next step. If A/C request indicator is not on, go to step 20 .
  6. Ensure blower motor switch is not in OFF position. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Connect fused jumper (3 amp) between A/C high pressure switch connector terminals. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 31 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 25 .
  7. If scan tool indicates A/C COMPRESSOR CYCLING SWITCH parameter is CLOSED, go to step 9 . If scan tool does not indicate A/C COMPRESSOR CYCLING SWITCH parameter is CLOSED, go to next step.
  8. Turn ignition switch to OFF position. Disconnect A/C low pressure switch. Connect fused jumper (3 amp) between A/C low pressure switch signal circuit (Dark Green wire) and ground. Start engine. Using scan tool, observe A/C COMPRESSOR CYCLING SWITCH parameter. If scan tool indicates A/C COMPRESSOR CYCLING SWITCH parameter is NORMAL, go to step 28 . If scan tool does not indicate A/C COMPRESSOR CYCLING SWITCH parameter is NORMAL, go to step 21 .
  9. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 15 . If A/C compressor clutch relay does not turn on and off with each command, go to next step.
  10. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 26 .
  11. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 27 . If test light does not turn on and off with each command, go to next step.
  12. If test light remains on with each command, go to step 14 . If test light does not remain on with each command, go to next step.
  13. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 32 .
  14. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 32 .
  15. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 17 .
  16. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 27 . If A/C compressor clutch does not engage, go to step 23 .
  17. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 39 .
  18. Check ignition voltage circuit (Brown wire) of HVAC control module for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to next step.
  19. Check ground circuit (Black wire) of HVAC control module for open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 30 .
  20. Ensure that blower motor switch is not in OFF position. Check off blower motor control circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 30 .
  21. Check A/C low pressure switch signal circuit (Dark Green wire) for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to next step.
  22. Check ground circuit (Black wire) of A/C low pressure switch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 32 .
  23. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to next step.
  24. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 29 .
  25. Turn ignition switch to OFF position. Reconnect A/C high pressure switch. Check A/C request signal circuit (Light Blue wire and Dark Green/White wire) for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 32 .
  26. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 39 .
  27. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 33 .
  28. Check A/C low pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 34 .
  29. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 36 .
  30. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 37 .
  31. Check A/C high pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 35 .
  32. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 39 . If problem was not found, go to step 38 .
  33. Replace A/C compressor clutch relay. After repairs, go to step 39 .
  34. Replace A/C low pressure switch. After repairs, go to step 39 .
  35. Replace A/C high pressure switch. After repairs, go to step 39 .
  36. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 39 .
  37. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 39 .
  38. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  39. Operate system to verify repair.
  1. Start engine. Place blower motor switch in OFF position. Place A/C request switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor clutch does not operate, problem is intermittent.
  2. Using scan tool, observe A/C REQUEST SIGNAL parameter in POWERTRAIN data list. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to next step. If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 5 .
  3. Check A/C request signal circuit (Light Blue wire and Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to next step.
  4. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 11 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 10 .
  5. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to next step. If A/C compressor clutch does not turn off, go to step 8 .
  6. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 9 .
  7. Check A/C clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 11 .
  8. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 13 .
  9. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 12 .
  10. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 14 .
  11. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 15 .
  12. Replace A/C compressor clutch relay. After repairs, go to step 16 .
  13. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 16 .
  14. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 16 .
  15. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  16. Operate system to verify repair.

4.3L, 5.0L, 5.7L, 6.5L & 8.1L: "G" SERIES (2001)

Note. For circuit, wire color and terminal identification, see WIRING DIAGRAMS . Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article.

Compressor Clutch Does Not Engage (Without 6.5L)

  1. Ensure outside air temperature is greater than 3°C (38°F). Start engine. Turn blower motor switch to maximum speed position. Place A/C request switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  2. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  3. If HVAC control assembly is inoperative, go to step 5 . If HVAC control assembly is not inoperative, go to next step.
  4. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter in ENGINE DATA 2 data list. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step 7 . If scan tool does not indicate A/C REQUEST SIGNAL parameter is YES, go to step 8 .
  5. Check voltage supply circuit (Brown wire) to HVAC control assembly for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to next step.
  6. Check ground circuit (Black wire) to HVAC control assembly for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to step 29 .
  7. If scan tool indicates A/C COMPRESSOR CYCLING SWITCH parameter is CLOSED, go to step 14 . If scan tool does not indicate A/C COMPRESSOR CYCLING SWITCH parameter is CLOSED, go to step 9 .
  8. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Connect fused jumper (3 amp) between A/C high pressure switch connector terminals. Start engine. Using scan tool, observe A/C REQUEST parameter. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST parameter is YES, go to step 30 . If scan tool does not indicate A/C REQUEST parameter is YES, go to step 10 .
  9. Turn ignition switch to OFF position. Disconnect A/C low pressure cutout switch. Connect fused jumper (3 amp) between A/C low pressure cutout switch signal connector terminals. Start engine. Using scan tool, observe A/C COMPRESSOR CYCLING SWITCH parameter. If scan tool indicates A/C COMPRESSOR CYCLING SWITCH parameter is CLOSED, go to step 27 . If scan tool does not indicate A/C COMPRESSOR CYCLING SWITCH parameter is CLOSED, go to step 12 .
  10. Turn ignition switch to OFF position. Reconnect A/C high pressure switch. Check A/C request signal circuit (Light Green wire and Dark Green/White wire) for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to next step.
  11. Measure voltage between A/C request signal circuit (Dark Green/White wire) at PCM an ground. If battery voltage is present, go to step 31 . If battery voltage is not present, go to step 29 .
  12. Check A/C low pressure switch signal circuit (Dark Green wire) for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to next step.
  13. Check ground circuit (Black wire) of A/C low pressure switch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to step 31 .
  14. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to next step. If A/C compressor clutch relay does not turn on and off with each command, go to step 17 .
  15. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit (Orange wire) of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 25 .
  16. Connect fused jumper (10 amp) between switch side voltage circuit (Orange wire) of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 27 . If A/C compressor clutch does not engage, go to step 20 .
  17. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. If test light is on , go to next step. If test light is off, go to step 24 .
  18. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 26 . If test light does not turn on and off with each command, go to next step.
  19. If test light remains on with each command, go to step 22 . If test light does not remain on with each command, go to step 23 .
  20. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to next step.
  21. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to step 28 .
  22. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to step 31 .
  23. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to step 31 .
  24. Repair coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. After repairs, go to step 38 .
  25. Repair switch side voltage supply circuit (Orange wire) of A/C compressor clutch relay. After repairs, go to step 38 .
  26. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to step 32 .
  27. Check A/C low pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to step 33 .
  28. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to step 35 .
  29. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to step 36 .
  30. Check A/C high pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to step 34 .
  31. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 38 . If problem was not found, go to step 37 .
  32. Replace A/C compressor clutch relay. After repairs, go to step 38 .
  33. Replace A/C low pressure switch. After repairs, go to step 38 .
  34. Replace A/C high pressure switch. After repairs, go to step 38 .
  35. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 38 .
  36. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 38 .
  37. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  38. Operate system to verify repair.

Compressor Clutch Does Not Engage (With 6.5L)

  1. Ensure ambient air temperature is greater than 3°C (38°F). Start engine. Turn blower motor switch to maximum speed position. Place A/C request switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step.
  2. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING.
  3. If HVAC control assembly is inoperative, go to step 5 . If HVAC control assembly is not inoperative, go to next step.
  4. Start engine. Using scan tool, observe A/C REQUEST parameter in ENGINE DATA 1 data list. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST parameter is ON, go to step 11 . If scan tool does not indicate A/C REQUEST parameter is ON, go to step 7 .
  5. Check voltage supply circuit (Brown wire) to HVAC control assembly for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to next step.
  6. Check ground circuit (Black wire) to HVAC control assembly for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 26 .
  7. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Connect fused jumper (3 amp) between A/C high pressure switch connector terminals. Start engine. Using scan tool, observe A/C REQUEST parameter. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST parameter is ON, go to step 27 . If scan tool does not indicate A/C REQUEST parameter is ON, go to next step.
  8. Turn ignition switch to OFF position. Disconnect A/C low pressure switch. Connect fused jumper (3 amp) between A/C low pressure switch connector terminals. Start engine. Using scan tool, observe A/C REQUEST parameter. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST parameter is ON, go to step 24 . If scan tool does not indicate A/C REQUEST parameter is ON, go to next step.
  9. Turn ignition switch to OFF position. Reconnect A/C high pressure switch. Reconnect A/C low pressure switch. Check A/C request signal circuit (Light Green wire, Dark Green wire and Dark Green/White wire) for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to next step.
  10. Measure voltage between A/C request signal circuit (Dark Green/White wire) at PCM and ground. If battery voltage is present, go to step 28 . If battery voltage is not present, go to step 26 .
  11. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to next step. If A/C compressor clutch relay does not turn on and off with each command, go to step 14 .
  12. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit (Orange wire) of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 22 .
  13. Connect fused jumper (10 amp) between switch side voltage circuit (Orange wire) of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 23 . If A/C compressor clutch does not engage, go to step 17 .
  14. Turn ignition to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 21 .
  15. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 23 . If test light does not turn on and off with each command, go to next step.
  16. If test light remains on with each command, go to step 19 . If test light does not remain on with each command, go to step 20 .
  17. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to next.
  18. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 25 .
  19. Check control circuit (Dark Green/White wire) of the A/C compressor clutch relay for a short to ground. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 28 .
  20. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 28 .
  21. Repair coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. After repairs, go to step 35 .
  22. Repair switch side voltage supply circuit (Orange wire) of A/C compressor clutch relay. After repairs, go to step 35 .
  23. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 29 .
  24. Check A/C low pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 30 .
  25. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 32 .
  26. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 33 .
  27. Check A/C high pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 31 .
  28. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 35 . If problem was not found, go to step 34 .
  29. Replace A/C compressor clutch relay. After repairs, go to step 35 .
  30. Replace A/C low pressure switch. After repairs, go to step 35 .
  31. Replace A/C high pressure switch. After repairs, go to step 35 .
  32. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 35 .
  33. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 35 .
  34. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  35. Operate system to verify repair.
  1. Start engine. Place blower motor switch in OFF position. Place A/C request switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent.
  2. Using scan tool, observe A/C REQUEST parameter in ENGINE DATA 2 data list. If scan tool indicates A/C REQUEST parameter is ON, go to next step. If scan tool does not indicate A/C REQUEST parameter is ON, go to step 5 .
  3. Check A/C request signal circuit (Dark Green/White wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to next step.
  4. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Start engine. Using scan tool, observe A/C REQUEST parameter. If scan tool indicates A/C REQUEST parameter is ON, go to step 11 . If scan tool does not indicate A/C REQUEST parameter is ON, go to step 10 .
  5. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to next step. If A/C compressor clutch does not turn off, go to step 8 .
  6. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 9 .
  7. Check A/C clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 11 .
  8. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 13 .
  9. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 12 .
  10. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 14 .
  11. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 16 . If problem was not found, go to step 15 .
  12. Replace A/C compressor clutch relay. After repairs, go to step 16 .
  13. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 16 .
  14. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 16 .
  15. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step.
  16. Operate system to verify repair.

A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Alero & Grand Am). Scheme 1

Scheme 1: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Alero & Grand Am)
Scheme 1: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Alero & Grand Am)

A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Alero & Grand Am 2.4L VIN T Engine). Scheme 2

Scheme 2: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Alero & Grand Am 2.4L VIN T Engine)
Scheme 2: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Alero & Grand Am 2.4L VIN T Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Alero & Grand Am 3.4L VIN E Engine). Scheme 3

Scheme 3: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Alero & Grand Am 3.4L VIN E Engine)
Scheme 3: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Alero & Grand Am 3.4L VIN E Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Astro & Safari). Scheme 4

Scheme 4: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Astro & Safari)
Scheme 4: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Astro & Safari)

A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Aurora). Scheme 5

Scheme 5: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Aurora)
Scheme 5: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Aurora)

A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Aztek). Scheme 6

Scheme 6: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Aztek)
Scheme 6: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Aztek)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Blazer, Jimmy, Sonoma & S10 Pickup - With Manual A/C-Heater System & 4.3L VINs W & X Engine). Scheme 7

Scheme 7: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Blazer, Jimmy, Sonoma & S10 Pickup - With Manual A/C-Heater System & 4.3L VINs W & X Engine)
Scheme 7: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Blazer, Jimmy, Sonoma & S10 Pickup - With Manual A/C-Heater System & 4.3L VINs W & X Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Blazer, Bravada, Envoy & Jimmy - With Automatic A/C-Heater System). Scheme 8

Scheme 8: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Blazer, Bravada, Envoy & Jimmy - With Automatic A/C-Heater System)
Scheme 8: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Blazer, Bravada, Envoy & Jimmy - With Automatic A/C-Heater System)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Bonneville & LeSabre). Scheme 9

Scheme 9: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Bonneville & LeSabre)
Scheme 9: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Bonneville & LeSabre)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000 "C" & "K" Pickup, Escalade, Tahoe & Yukon - 5.7L VIN R & 7.4 VIN J). Scheme 10

Scheme 10: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 "C" & "K" Pickup, Escalade, Tahoe & Yukon - 5.7L VIN R & 7.4 VIN J)
Scheme 10: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 "C" & "K" Pickup, Escalade, Tahoe & Yukon - 5.7L VIN R & 7.4 VIN J)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000 "C" & "K" Pickup - Diesel Engine). Scheme 11

Scheme 11: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 "C" & "K" Pickup - Diesel Engine)
Scheme 11: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 "C" & "K" Pickup - Diesel Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Camaro & Firebird - With 3.8L VIN K Engine). Scheme 12

Scheme 12: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Camaro & Firebird - With 3.8L VIN K Engine)
Scheme 12: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Camaro & Firebird - With 3.8L VIN K Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Camaro & Firebird - With 5.7L VIN G Engine). Scheme 13

Scheme 13: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Camaro & Firebird - With 5.7L VIN G Engine)
Scheme 13: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Camaro & Firebird - With 5.7L VIN G Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Catera). Scheme 14

Scheme 14: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Catera)
Scheme 14: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Catera)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Cavalier & Sunfire). Scheme 15

Scheme 15: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Cavalier & Sunfire)
Scheme 15: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Cavalier & Sunfire)

A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Cavalier & Sunfire). Scheme 16

Scheme 16: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Cavalier & Sunfire)
Scheme 16: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Cavalier & Sunfire)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Century & Regal). Scheme 17

Scheme 17: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Century & Regal)
Scheme 17: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Century & Regal)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Corvette). Scheme 18

Scheme 18: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Corvette)
Scheme 18: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Corvette)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000 DeVille). Scheme 19

Scheme 19: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 DeVille)
Scheme 19: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 DeVille)

A/C Compressor Clutch Control Circuit Wiring Diagram (2001 DeVille). Scheme 20

Scheme 20: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 DeVille)
Scheme 20: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 DeVille)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Eldorado). Scheme 21

Scheme 21: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Eldorado)
Scheme 21: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Eldorado)

A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Eldorado). Scheme 22

Scheme 22: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Eldorado)
Scheme 22: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Eldorado)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Express & Savana - Except Diesel Engine). Scheme 23

Scheme 23: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Express & Savana - Except Diesel Engine)
Scheme 23: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Express & Savana - Except Diesel Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Express & Savana - Diesel Engine). Scheme 24

Scheme 24: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Express & Savana - Diesel Engine)
Scheme 24: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Express & Savana - Diesel Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Express & Savana - Except Diesel Engine). Scheme 25

Scheme 25: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Express & Savana - Except Diesel Engine)
Scheme 25: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Express & Savana - Except Diesel Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Express & Savana - Diesel Engine). Scheme 26

Scheme 26: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Express & Savana - Diesel Engine)
Scheme 26: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Express & Savana - Diesel Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Grand Prix). Scheme 27

Scheme 27: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Grand Prix)
Scheme 27: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Grand Prix)

A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Grand Prix). Scheme 28

Scheme 28: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Grand Prix)
Scheme 28: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Grand Prix)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Impala & Monte Carlo). Scheme 29

Scheme 29: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Impala & Monte Carlo)
Scheme 29: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Impala & Monte Carlo)

A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Impala & Monte Carlo). Scheme 30

Scheme 30: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Impala & Monte Carlo)
Scheme 30: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Impala & Monte Carlo)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Intrigue). Scheme 31

Scheme 31: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Intrigue)
Scheme 31: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Intrigue)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Lumina). Scheme 32

Scheme 32: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Lumina)
Scheme 32: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Lumina)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Malibu). Scheme 33

Scheme 33: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Malibu)
Scheme 33: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Malibu)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Montana, Silhouette & Venture). Scheme 34

Scheme 34: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Montana, Silhouette & Venture)
Scheme 34: A/C Compressor Clutch Control Circuit Wiring Diagram (2000 Montana, Silhouette & Venture)

A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Montana, Silhouette & Venture). Scheme 35

Scheme 35: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Montana, Silhouette & Venture)
Scheme 35: A/C Compressor Clutch Control Circuit Wiring Diagram (2001 Montana, Silhouette & Venture)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Park Avenue). Scheme 36

Scheme 36: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Park Avenue)
Scheme 36: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Park Avenue)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Seville). Scheme 37

Scheme 37: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Seville)
Scheme 37: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Seville)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Sierra, Silverado, Suburban, Tahoe, Yukon & Yukon XL). Scheme 38

Scheme 38: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Sierra, Silverado, Suburban, Tahoe, Yukon & Yukon XL)
Scheme 38: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Sierra, Silverado, Suburban, Tahoe, Yukon & Yukon XL)

A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Sonoma & S10 Pickup - 2.2L VIN 4 & VIN 5 Engine). Scheme 39

Scheme 39: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Sonoma & S10 Pickup - 2.2L VIN 4 & VIN 5 Engine)
Scheme 39: A/C Compressor Clutch Control Circuit Wiring Diagram (2000-01 Sonoma & S10 Pickup - 2.2L VIN 4 & VIN 5 Engine)

More articles — HVAC System - Compressor Clutch Controls