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HVAC System - Compressor Clutch Controls GMC Savana I

A/c Compressor 23 illustrations ~25044 words

MODEL IDENTIFICATION

Note. Metro, Prizm and Tracker, and Saturn are not covered in this article. For A/C compressor clutch diagnosis on Metro, Prizm, Tracker, and Saturn, see appropriate MANUAL A/C-HEATER SYSTEMS article.

Body Code (1)Model
CPark Avenue
EEldorado
FCamaro & Firebird
GAurora & Riviera
HBonneville, Eighty Eight & LeSabre
JCavalier & Sunfire
KDeVille & Seville
NAlero, Cutlass, Grand Am & Malibu
VCatera
WCentury, Grand Prix, Intrigue, Lumina, Monte Carlo & Regal
YCorvette
(1) Vehicle body code is fourth character of VIN.
(1)Vehicle body code is fourth character of VIN.

MODEL IDENTIFICATION (CARS)

Series (1)Model(s)
C2WD - Pickup, Sierra, Suburban, Tahoe, Silverado & Yukon
GExpress & Savana
K4WD - Pickup, Escalade, Sierra, Suburban, Tahoe, Silverado & Yukon
LAWD Astro & Safari
M2WD Astro & Safari
PCommercial Chassis/Motorhome
S2WD - Blazer, Jimmy, Pickup & Sonoma
T4WD - Blazer, Bravada, Jimmy, Pickup & Sonoma
UMontana, Silhouette & Venture
(1) Vehicle series code is fifth character of VIN.
(1)Vehicle series code is fifth character of VIN.

MODEL IDENTIFICATION (LIGHT TRUCKS & VANS)

Except Catera

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

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

The A/C clutch relay is controlled by PCM. This allows PCM 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 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.

Catera

When A/C button on A/C-heater control panel is pressed, an A/C request signal is sent through the refrigerant pressure switch and Engine Control Module (ECM) to the coil of A/C clutch relay (K60). The A/C clutch relay is located at left front of engine compartment, in ECM housing. This enables A/C clutch relay to energize, allowing ignition voltage to energize compressor clutch coil and fan control relay (K87).

When fan control relay energizes, battery voltage is supplied to auxiliary cooling fan No. 1 and through the normally open contacts of fan control relay (K52), to auxiliary cooling fan No. 2. If coolant temperature reaches 248°F (120°C), secondary temperature switch contacts will open and the compressor clutch coil is disengaged, causing A/C system to turn off. Secondary temperature switch will not allow A/C system to turn back on until coolant temperature has dropped to 239°F (115°C) or less.

Compressor clutch coil can also be turned off by refrigerant pressure switches (low pressure switch or high pressure switch). Low pressure switch will turn compressor clutch off as soon as refrigerant pressure falls to about 26 psi (1.8 kg/cm 2 ). This is done by opening low pressure switch contacts and not allowing battery voltage to pass through A/C clutch relay (K60) to compressor clutch coil. Low pressure switch activates the compressor clutch when refrigerant pressure increases to about 36.3 psi (2.6 kg/cm 2 ).

High pressure switch will turn compressor clutch off as soon as refrigerant pressure exceeds 435 psi (30.6 kg/cm 2 ). This is done by opening high pressure switch contacts in refrigerant pressure switch and not allowing battery voltage to pass through A/C clutch relay (K60) to compressor clutch. High pressure switch activates compressor clutch when refrigerant pressure drops less than about 290 psi (19.3 kg/cm 2 ).

When refrigerant pressure exceeds 159.4 psi (11.2 kg/cm 2 ), A/C control switch contacts will close and engine idle speed will increase to compensate for RPM drop that occurs when A/C system is switched on. A/C control switch is installed in high pressure line, between A/C compressor and condenser. When refrigerant pressure drops less than about 130.5 psi (9.2 kg/cm 2 ), the A/C control switch contacts will close and allow engine idle speed to return to normal.

ApplicationLocation
C BodyRight Front Of Engine Compartment, In Fuse/Relay Block
E & K BodiesIn Underhood Fuse/Relay Block
F BodyIn Underhood Electrical Center, On Left Inner Fender Panel
G BodyIn Underhood Relay Center, At Right Front Of Engine Compartment
H BodyCenter Rear Of Engine Compartment, Below Right Fuse Block
J BodyIn Underhood Fuse/Relay Block, At Left Front Of Engine Compartment
N BodyAt Right Rear Of Engine Compartment
V BodyLeft Front of Engine Compartment, In ECM Housing
W BodyIn Underhood Electrical Center, At Right Front 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.

Note. Astro and Safari are equipped with a Vehicle Control Module (VCM). Substitute PCM with VCM in the following system description as necessary.

RWD Trucks & Vans

The A/C clutch relay is controlled by PCM. The PCM 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. The PCM smooths cycling of compressor clutch by adding fuel the instant compressor clutch is applied.

Application (1)Location
C & K SeriesIn Underhood Fuse/Relay Center, Left Rear Of Engine Compartment
S & T SeriesIn Underhood Fuse Block
G SeriesIn Underhood Fuse/Relay Center, Left Front Of Engine Compartment
Sierra & SilveradoIn Underhood Bussed Electrical Center
L & M SeriesIn Underhood Fuse/Relay Center, Left Side Of Engine Compartment
U BodyIn Underhood Accessory Wiring Junction Block
(1) "P" series A/C clutch relay location will vary with coach builder. See coach manufacturer's information for location.
(1)"P" series A/C clutch relay location will vary with coach builder. See coach manufacturer's information for location.

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

A/C CLUTCH CIRCUIT DIAGNOSIS (CARS)

To help save diagnostic time, ALWAYS check for blown fuses or fusible links before proceeding with diagnosis. If fuses are blown, locate and repair short circuit before replacing fuses.

Ensure all related relay and wire harness connections are clean and tight. Repair as necessary. See WIRING DIAGRAMS .

Note. Vehicles may be equipped with a PCM using an Electronically Erasable Programmable Read Only Memory (EEPROM). When replacing PCM, the new PCM must be programmed.

Description

Powertrain Control Module (PCM) receives an A/C request signal from Instrument Panel Cluster (IPC) over UART serial data line. When A/C is requested, the PCM provides a ground path to A/C clutch relay control circuit. When relay circuit is grounded, A/C clutch relay is energized. PCM delays grounding relay circuit for .3 seconds. This allows PCM to adjust engine idle RPM for additional load.

PCM will temporarily de-energize A/C clutch relay when one or more of the following conditions occur

  1. A hot engine restart.
  2. Wide open throttle (TPS position over 90 percent).
  3. If engine RPM is greater than 6000 RPM.
  4. During Idle Air Control (IAC) valve reset

A/C clutch relay will remain de-energized when one or both of the following conditions occur

  1. DTC P0530 or U1016 are set.
  2. When there is no A/C request signal to PCM.

For additional trouble shooting information, go to MANUAL A/C-HEATER SYSTEMS - CAVALIER & SUNFIRE article.

Diagnostic Aids

If DTCs P0530 or U1060 are set, diagnose them before proceeding. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If problem is insufficient cooling, check cooling fans for proper operation. See ELECTRIC COOLING FANS - ALL MODELS article. If cooling fans operate correctly, diagnose manual A/C-heater system. See MANUAL A/C-HEATER SYSTEMS - CAVALIER & SUNFIRE article.

An A/C refrigerant pressure less than 43 psi (3.0 kg/cm 2 ), or greater than 428 psi (30.1 kg/cm 2 ), will cause PCM to disable compressor clutch. With engine running and A/C on, use scan tool to monitor A/C high-side pressure for 2 minutes. If pressure goes out of range, diagnose manual A/C-heater system.

Diagnosis

  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Install scan tool. Check for any DTCs that may be set. If DTC P0530 or U1016 are set, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no DTCs are set, go to next step.
  3. If A/C compressor clutch is engaged, go to next step. If A/C compressor clutch is not engaged, go to step 5 .
  4. Remove A/C clutch relay. If A/C compressor clutch disengages, go to step 6) . If A/C compressor clutch does not disengage, go to step 7 .
  5. Start engine and allow it to reach normal operating temperature. Cycle A/C on and off at control panel. If A/C compressor clutch cycles on and off, go to step 8 . If A/C compressor clutch does not cycle on and off, go to step 9 .
  6. Using a test light connected to battery voltage, probe A/C clutch relay control circuit terminal (Dark Green/White wire) at A/C clutch relay connector. See «WIRING DIAGRAMS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__wiring-diagrams) . If test light comes on, go to step 10 . If test light does not come on, go to step 11 .
  7. Disconnect A/C compressor clutch harness connector. If A/C compressor clutch disengages, go to step 12 . If A/C compressor clutch does not disengage, go to step 13 .
  8. Turn ignition switch to OFF position. Install A/C manifold gauge set. Compare high-side pressure reading on gauge with scan tool reading. If readings are within 20 psi (1.4 kg/cm 2 ) of each other, go to step 36 . If readings are not as specified, go to step 14 .
  9. While observing scan tool, turn A/C on, then off. If scan tool indicates A/C was requested, then not requested, go to step 15 . If operation is not as specified, go to step 16 .
  10. Check Dark Green/White wire for a short to ground. Repair as necessary. Go to step 36 . If no problem is found, go to step 17 .
  11. Replace A/C clutch relay. Go to step 36 .
  12. Repair short to battery voltage in A/C compressor clutch battery feed circuit (Dark Green wire). Go to step 36 .
  13. Replace A/C compressor clutch coil. Go to step 36 .
  14. Disconnect A/C pressure sensor harness connector. Using a DVOM, measure voltage between battery positive terminal and A/C pressure sensor ground circuit (Black wire). If battery voltage is indicated, go to step 18 . If battery voltage is not indicated, go to step 19 .
  15. Turn engine off, ignition on. Observe high-side pressure reading on scan tool. If reading is 40-430 psi (2.8-30.2 kg/cm 2 ), go to step 20 . If reading is not as specified, go to step 21 .
  16. Using a test light connected to ground, probe A/C selector switch input circuit (Light Green wire) at Instrument Panel Cluster (IPC) microprocessor. Cycle A/C selector on, then off. If test light toggles on, then off, go to step 22 . If operation is not as specified, go to step 23 .
  17. Turn ignition switch to OFF position. Replace PCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE - DOMESTIC CARS, LIGHT TRUCKS & VANS manual. Go to step 36 .
  18. Replace A/C pressure sensor. Go to step 36 .
  19. Repair open or poor connection in A/C pressure sensor ground circuit (Black wire). Go to step 36 .
  20. Disconnect A/C clutch relay. Using a test light connected to ground, probe A/C clutch relay battery and ignition feed terminals. If test light comes on at both terminals, go to step 24 . If test light does not come on at both terminals, go to step 25 .
  21. Install A/C manifold gauge set. Turn ignition on, engine off. Compare high-side pressure reading on gauge with scan tool reading. If readings are within 20 psi (1.4 kg/cm 2 ) of each other, diagnose A/C-heater system. See MANUAL A/C-HEATER SYSTEMS - CAVALIER & SUNFIRE article. If readings are not as specified, go to step 18 .
  22. Replace IPC. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Go to step 36 .
  23. Repair signal circuit (Light Green wire) from A/C selector switch to IPC microprocessor. Go to step 36 .
  24. Connect a fused jumper wire between A/C relay battery feed terminal and A/C compressor clutch battery feed terminal (Dark Green wire). If A/C compressor clutch engages, go to step 26 . If A/C compressor clutch does not engage, leave jumper wire installed and go to step 27 .
  25. Check for a short to ground in A/C compressor clutch battery feed circuit (Dark Green wire). Also, check for a faulty A/C compressor clutch diode. Repair as necessary. Go to step 36 . If no problem is found, go to step 28 .
  26. Remove jumper wire. Start engine and let idle. Using a test light connected to battery voltage, probe A/C clutch relay control circuit terminal (Dark Green/White wire). Using scan tool, command relay on. If test light comes on, go to step 11 . If test light does not come on, go to step 29 .
  27. Disconnect A/C compressor clutch harness connector. Using a test light connected to ground, probe A/C compressor clutch battery feed circuit (Dark Green wire). If test light comes on, go to step 30 . If test light does not come on, go to step 31 .
  28. Turn ignition switch to OFF position. Repair open in battery or ignition feed circuits to A/C clutch relay. Go to step 36 . If circuits are okay, go to step 11 .
  29. Using a test light connected to ground, probe A/C clutch relay control circuit terminal (Dark Green/White wire) at A/C clutch relay connector. If test light comes on, go to step 32 . If test light does not come on, go to step 33 .
  30. Using a test light connected to battery voltage, probe A/C compressor clutch ground circuit (Black wire). If test light comes on, go to step 34 . If test light does not come on, go to step 35 .
  31. Turn ignition switch to OFF position. Repair open in A/C compressor clutch battery feed circuit (Dark Green wire). Go to step 36 .
  32. Check A/C clutch relay control circuit (Dark Green/White wire) for a short to voltage. Repair as necessary. Go to step 36 . If no problem is found, go to step 17 .
  33. Check for an open or poor connection in A/C clutch relay control circuit (Dark Green/White wire). Repair as necessary. Go to step 36 . If no problem is found, go to step 17 .
  34. Turn ignition switch to OFF position. Replace A/C compressor clutch coil. Go to step 36 .
  35. Repair open or poor connection in A/C compressor clutch ground circuit (Black wire). Go to next step.
  36. Start engine and let idle. Cycle A/C selector on, then off. If A/C compressor clutch cycles on, then off, system is okay at this time. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__diagnostic-aids) . If A/C compressor clutch does not cycle as specified, go to step 2 .

2.4L: ALERO, GRAND AM & MALIBU

Note. Body Function Controller (BFC) may also be referred to as a Body Control Module (BCM).

Powertrain Control Module (PCM) receives an A/C request signal from Body Control Module (BCM) over Class 2 serial data line. When A/C is requested, PCM provides a ground path to A/C clutch relay control circuit. When relay circuit is grounded, A/C clutch relay is energized. The PCM delays grounding relay circuit for .3 seconds. This allows PCM to adjust engine idle RPM for additional load.

The PCM will temporarily de-energize A/C clutch relay when one or more of the following conditions occur

  1. A hot engine restart.
  2. Wide open throttle (TPS position over 90 percent).
  3. If engine RPM is greater than 6000 RPM.
  4. During Idle Air Control (IAC) valve reset.

A/C clutch relay will remain de-energized when one or both of the following conditions occur

  1. DTC P0530 or U1016 are set.
  2. When there is no A/C request signal to PCM.

For additional trouble shooting information, go to appropriate MANUAL A/C-HEATER SYSTEMS article.

If DTCs P0530, U1016 or U1064 are set, diagnose them before proceeding. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If problem is insufficient cooling, check cooling fans for proper operation. See ELECTRIC COOLING FANS - ALL MODELS article. If cooling fans operate correctly, diagnose manual A/C-heater system. See appropriate MANUAL A/C-HEATER SYSTEMS article.

An A/C refrigerant pressure less than 43 psi (3.0 kg/cm 2 ), or greater than 428 psi (30.1 kg/cm 2 ), will cause PCM to disable A/C compressor clutch. With engine running and A/C on, use scan tool to monitor A/C high-side system pressure for 2 minutes. If pressure goes out of range, diagnose manual A/C-heater system. See appropriate MANUAL A/C-HEATER SYSTEMS article.

  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Turn ignition switch to OFF position. Install scan tool. If any DTCs are set, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no DTCs are set, go to next step.
  3. If A/C compressor clutch is engaged, go to next step. If AC compressor clutch is not engaged, go to step 5 .
  4. Disconnect A/C clutch relay. If A/C compressor clutch disengages, go to step 6 . If A/C compressor clutch does not disengage, go to step 7 .
  5. Start engine and allow it to reach normal operating temperature. Cycle A/C on and off at control panel while observing scan tool. If scan tool indicates A/C is requested when A/C is on, go to step 16 . If scan tool does not indicate as specified, go to step 12 .
  6. Using a test light connected to battery voltage, probe A/C clutch relay control circuit terminal (Dark Green/White wire) at A/C clutch relay connector. See «WIRING DIAGRAMS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__wiring-diagrams) . If test light comes on, go to step 8 . If test light does not come on, go to step 9 .
  7. Disconnect A/C compressor clutch harness connector. If A/C compressor clutch disengages, go to step 10 . If A/C compressor clutch does not disengage, go to step 11 .
  8. Turn ignition switch to OFF position. Check A/C clutch relay control circuit (Dark Green/White wire) for a short to ground. Repair as necessary. Go to step 43 . If no problem is found, go to step 34 .
  9. Turn ignition switch to OFF position. Replace A/C clutch relay. Go to step 43 .
  10. Turn ignition switch to OFF position. Repair A/C compressor clutch battery feed circuit (Dark Green wire) for a short to voltage. Go to step 43 .
  11. Turn ignition switch to OFF position. Replace A/C compressor clutch. Go to step 43 .
  12. Using scan tool, monitor BCM serial data while commanding A/C selector switch on and off. If scan tool indicates a change when commanded on and off, go to step 35 . If scan tool does not indicate a change, go to next step.
  13. Using a test light connected to ground, probe A/C selector switch input circuit (Light Green wire) at BCM harness connector. Cycle A/C selector switch on and off. If test light toggles on and off, go to next step. If test light does not toggle on and off, go to step 15 .
  14. Turn ignition switch to OFF position. Diagnose BCM system. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. Go to step 43 .
  15. Turn ignition switch to OFF position. Repair A/C request signal circuit (Light Green wire) between A/C heater control assembly and BCM. Go to step 43 .
  16. Cycle A/C selector switch on and off. If A/C compressor clutch cycles on and off, go to step 29 . If A/C compressor clutch does not cycle on and off, go to next step.
  17. Turn ignition switch to OFF position. Disconnect A/C clutch relay. Using a test light connected to ground, probe A/C clutch relay battery and ignition feed terminals at A/C clutch relay connector. Turn ignition switch to OFF position. If test light comes on at both terminals, go to next step. If test light does not come on at both terminals, go to step 19 .
  18. Connect a fused jumper wire between A/C clutch relay battery feed terminal and A/C compressor clutch battery feed terminal. If A/C compressor clutch engages, go to step 20 . If A/C compressor clutch does not engage, go to step 21 .
  19. Turn ignition switch to OFF position. Check A/C compressor clutch battery feed circuit (Dark/Green wire) for a short to ground. Also, check for an open in A/C compressor clutch diode. Repair as necessary. Go to step 43 . If no problem is found, go to step 22 .
  20. Remove jumper wire. Start engine and let idle. Using a test light connected to battery voltage, probe A/C clutch relay control circuit terminal (Dark Green/White wire) at A/C clutch relay connector. Using scan tool, command A/C clutch relay on. If test light comes on, go to step 9 . If test light does not come on, go to step 23 .
  21. With jumper wire installed, disconnect A/C compressor clutch harness connector. Using a test light connected to ground, probe A/C compressor clutch battery feed terminal (Dark Green wire). If test light comes on, go to step 24 . If test light does not come on, go to step 25 .
  22. Turn ignition switch to OFF position. Repair open in battery or ignition feed circuit to A/C clutch relay. Go to step 43 .
  23. Using a test light connected to ground, probe A/C clutch relay control circuit terminal (Dark Green/White wire) at A/C clutch relay connector. If test light comes on, go to step 26 . If test light does not come on, go to step 27 .
  24. Using a test light connected to battery voltage, probe A/C compressor clutch ground circuit terminal (Black wire). If test light comes on, go to step 11 . If test light does not come on, go to step 28 .
  25. Turn ignition switch to OFF position. Repair open in A/C compressor clutch battery feed circuit (Dark Green wire). Go to step 43 .
  26. Turn ignition switch to OFF position. Check A/C clutch relay control circuit (Dark Green/White wire) for a short to voltage. Repair as necessary. Go to step 43 . If no problem is found, go to step 34 .
  27. Turn ignition switch to OFF position. Check A/C clutch relay control circuit (Dark Green/White wire) for an open or poor connection. Repair as necessary. Go to step 43 . If no problem is found, go to step 34 .
  28. Turn ignition switch to OFF position. Repair open or poor connection in a/C compressor clutch ground circuit (Black wire). Go to step 43 .
  29. Turn ignition on, engine off. Observe high-side pressure reading on scan tool. If reading is 40-430 psi (2.8-30.2 kg/cm 2 ), go to step 43 . If reading is not as specified, go to next step.
  30. Disconnect A/C pressure sensor harness connector. Using a test light connected to battery voltage, probe A/C pressure sensor ground circuit terminal (Black wire). If test light comes on, go to next step. If test light does not come on, go to step 33 .
  31. Install A/C manifold gauge set. Turn ignition on, engine off. Compare high-side pressure reading on gauge with scan tool reading. If readings are within 20 psi (1.4 kg/cm 2 ) of each other, diagnose manual A/C-heater system. See appropriate MANUAL A/C-HEATER SYSTEMS article. If readings are not as specified, go to next step.
  32. Check A/C pressure sensor harness connector for a poor connection. Repair as necessary. If no problem is found, replace A/C pressure sensor. Go to step 43 .
  33. Repair open or poor connection in A/C pressure sensor ground circuit (Black wire). Go to step 43 .
  34. Replace PCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Go to step 43 .
  35. Turn ignition on, engine off. Observe high-side pressure reading on scan tool. If reading is 40-430 psi (2.8-30.2 kg/cm 2 ), diagnose BCM system. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If reading is not as specified, go to next step.
  36. Install A/C manifold gauge set. Turn ignition on, engine off. Compare high-side pressure reading on gauge with scan tool reading. If readings are within 20 psi (1.4 kg/cm 2 ) of each other, diagnose manual A/C-heater system. See appropriate MANUAL A/C-HEATER SYSTEMS article. If readings are not as specified, go to next step.
  37. Disconnect A/C pressure sensor harness connector. If scan tool displays A/C high-side pressure as less than 421 psi (29.6 kg/cm 2 ), or A/C refrigerant pressure sensor reads less than one volt, go to next step. If scan tool display is not as specified, go to step 41 .
  38. Using a DVOM connected to ground, probe A/C pressure sensor reference voltage circuit terminal (Gray wire). If reading is 5 volts, go to next step. If reading is not as specified, go to step 40 .
  39. Connect a jumper wire between Gray wire and Red/Black wire of A/C pressure sensor harness connector. If scan tool displays A/C high-side pressure as greater than 421 psi (29.6 kg/cm 2 ), or A/C refrigerant pressure sensor reads greater than 4.6 volts, go to step 32 . If scan tool display is not as specified, go to step 42 .
  40. Turn ignition switch to OFF position. Check A/C pressure sensor reference voltage circuit (Gray wire) for an open or poor connection. Repair as necessary. Go to step 43 . If no problem is found, go to step 34 .
  41. Turn ignition switch to OFF position. Check A/C pressure sensor signal circuit (Red/Black wire) for a short to voltage. Repair as necessary. Go to step 43 . If no problem is found, go to step 34 .
  42. Turn ignition switch to OFF position. Check A/C pressure sensor signal circuit (Red/Black wire) for an open, short to ground, or poor connection. Repair as necessary. Go to next step. If no problem is found, go to step 34 .
  43. Start engine and let idle. Cycle A/C selector on, then off. If A/C compressor clutch cycles on, then off, system is okay at this time. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) . If A/C compressor clutch does not cycle as specified, go to step 2 .

3.0L: CATERA

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.

Description (A/C Request Circuit)

For proper A/C system operation, the A/C request circuit monitors selected A/C mode, A/C system pressure and throttle position. When A/C mode is selected with A/C system pressure and throttle angle at a predetermined value, Engine Control Module (ECM) energizes A/C clutch relay through A/C clutch relay control circuit. The ECM de-energizes A/C clutch relay during wide open throttle, when engine coolant temperature or A/C system pressure exceeds a predetermined threshold, or when a non-A/C mode is selected. If system does not operate as specified, see A/C REQUEST CIRCUIT DIAGNOSIS .

Description (A/C Load Signal Circuit)

The ECM receives a signal from the A/C load signal circuit. A normally open pressure switch connected to battery voltage monitors A/C system operating pressures. If pressures reach approximately 175 psi (12.2 kg/cm 2 ) the switch will close, sending a signal to the ECM. The ECM will raise idle speed around 50 RPM to compensate for the additional load. If system does not operate as specified, see A/C LOAD SIGNAL CIRCUIT DIAGNOSIS .

Description (A/C Compressor Control Circuit)

The ECM controls the ground side of the A/C clutch relay to energize the A/C compressor clutch. When component is commanded on by the ECM, voltage on the control circuit should be at or near zero volts. When component is commanded off by the ECM, voltage on the control circuit should be at or near battery voltage. If system does not operate as specified, see A/C COMPRESSOR CONTROL CIRCUIT DIAGNOSIS .

A/C Request Circuit Diagnosis

  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Start engine and let idle. While observing A/C REQUEST on scan tool display, turn A/C on and off. If A/C REQUEST toggles between YES and NO, A/C request circuit is okay at this time. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) . If A/C REQUEST does not toggle between YES and NO, go to next step.
  3. If A/C REQUEST is always YES, go to next step. If A/C REQUEST is always NO, go to step 5 .
  4. Disconnect A/C pressure switch harness connector. If A/C REQUEST changes to NO, diagnose A/C-heater system. See AUTOMATIC A/C-HEATER SYSTEMS - CATERA article. If A/C REQUEST remains as YES, go to step 6 .
  5. Turn ignition on, engine off. Disconnect A/C pressure switch harness connector. Using a fused jumper wire connected to battery voltage, probe terminal No. 1 (A/C request circuit) at A/C pressure switch harness connector. See «WIRING DIAGRAMS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__wiring-diagrams) . If A/C REQUEST changes to YES, diagnose A/C-heater system. See AUTOMATIC A/C-HEATER SYSTEMS - CATERA article. If A/C REQUEST remains as NO, go to next step.
  6. Turn ignition switch to OFF position. Disconnect ECM harness connectors. Turn ignition on, engine off. Using a DVOM, check A/C request circuit (Black/White wire) between ECM and A/C pressure switch for an open, short to voltage, or short to ground. Repair as necessary. Go to step 9 . If no problem is found, go to next step.
  7. Check for poor harness connections at ECM. Repair as necessary. Go to step 9 . If no problem is found, go to next step.
  8. Replace ECM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Go to next step.
  9. Start engine and let idle. While observing A/C REQUEST on scan tool display, turn A/C on and off. If A/C REQUEST toggles between YES and NO, A/C request circuit is okay. If A/C REQUEST does not toggle between YES and NO, go to step 2 .

A/C Load Signal Circuit Diagnosis

  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Start engine and let idle. With A/C off, observe A/C LOAD SIGNAL on scan tool display. If A/C LOAD SIGNAL indicates HEAVY, go to next step. If A/C LOAD SIGNAL does not indicate HEAVY, go to step 4 .
  3. Disconnect A/C load switch harness connector. If A/C LOAD SIGNAL changes to NORMAL, go to step 10 . If A/C LOAD SIGNAL does not change to NORMAL, go to step 8 .
  4. Turn ignition on, engine off. Disconnect A/C load switch harness connector. Using a test light connected to ground, probe ignition feed circuit (Brown wire) in A/C load switch harness connector. See «WIRING DIAGRAMS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__wiring-diagrams) . If test light comes on, go to next step. If test light does not come on, go to step 9 .
  5. Using a fused jumper wire, jumper A/C load switch harness connector terminals together. Observe scan tool. If A/C LOAD SIGNAL changes to HEAVY, go to next step. If A/C LOAD SIGNAL does not change to HEAVY, go to step 8 .
  6. Check for poor terminal connections at A/C load switch harness connector. Repair as necessary. Go to step 13 . If no problem is found, go to next step.
  7. Install A/C manifold gauge set. Start engine and turn A/C on. Increase engine speed to 2000 RPM. Observe A/C LOAD SIGNAL on scan tool and high-side pressure on gauge. If A/C LOAD SIGNAL changes to HEAVY when high-side pressure reaches 174 psi (12.2 kg/cm 2 ), A/C load signal circuit is okay at this time. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) . If A/C LOAD SIGNAL does not change to HEAVY, go to step 10 .
  8. Turn ignition switch to OFF position. Disconnect ECM harness connectors. Turn ignition on, engine off. Using a DVOM, check A/C load signal circuit (Black/Blue wire) between ECM and A/C load switch for an open, short to ground, or short to voltage. Repair as necessary. Go to step 13 . If no problem is found, go to step 11 .
  9. Repair open or high resistance in ignition feed circuit (Brown wire) to A/C load switch. Go to step 13 .
  10. Replace A/C load switch. Go to step 13 .
  11. Check for poor terminal connections at ECM. Repair as necessary. Go to step 13 . If no problem is found go to next step.
  12. Replace ECM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Go to next step.
  13. Start engine and let idle. Turn A/C off. Observe A/C LOAD SIGNAL on scan tool display. If A/C LOAD SIGNAL indicates HEAVY, go to step 2 . If A/C LOAD SIGNAL does not indicate HEAVY, go to next step.
  14. Disconnect A/C load switch harness connector. Observe scan tool display. If A/C LOAD SIGNAL changes to NORMAL, go to next step. If A/C LOAD SIGNAL does not change to NORMAL, go to step 2 .
  15. Using a fused jumper wire, jumper A/C load switch harness connector terminals. Observe scan tool display. If A/C LOAD SIGNAL changes to HEAVY, A/C load signal circuit is okay. If A/C LOAD SIGNAL does not change to HEAVY, go to step 2 .

A/C Compressor Control Circuit Diagnosis

  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Turn ignition on, engine off. Using scan tool, command A/C clutch relay on and off. If A/C clutch relay turns on and off, go to next step. If A/C clutch relay does not turn on and off, go to step 5 .
  3. Turn ignition switch to OFF position. Disconnect ECM harness connectors. Turn ignition on, engine off. Using a DVOM on 10-amp scale, measure current from A/C clutch relay control circuit (Brown/Purple wire) at ECM harness connector to ground for 2 minutes. See «WIRING DIAGRAMS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__wiring-diagrams) . If current draw is 0.1-0.75 amp, A/C compressor control circuit is okay. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) . If current draw is not as specified, go to next step.
  4. Turn ignition switch to OFF position. Disconnect A/C clutch relay. Using a DVOM, measure resistance between ground and A/C clutch relay control circuit (Brown/Purple wire) at ECM harness connector. If resistance is infinite, go to step 11 . If resistance is not as specified, go to step 9 .
  5. Turn ignition switch to OFF position. Disconnect A/C clutch relay. Connect a test light between Brown wire and Brown/Purple wire at A/C clutch relay harness connector. Turn ignition switch to ON position. Using scan tool, command A/C clutch relay on and off. If test light flashes on and off, go to step 8 . If test light does not flash on and off, go to next step.
  6. Using a test light connected to ground, probe ignition feed circuit (Red wire) at A/C clutch relay harness connector. If test light comes on, go to next step. If test light does not come on, go to step 10 .
  7. Turn ignition switch to OFF position. Reconnect A/C clutch relay. Disconnect ECM harness connectors. Turn ignition on, engine off. Using a fused jumper wire connected to ground, probe A/C clutch relay control circuit (Brown/Purple wire) at ECM harness connector. If A/C clutch relay operates, go to step 12 . If A/C clutch relay does not operate, go to step 9 .
  8. Check for poor connections at A/C clutch relay. Repair as necessary. Go to step 14 . If no problem is found, go to step 11 .
  9. Repair A/C clutch relay control circuit (Brown/Purple wire). Go to step 14 .
  10. Repair ignition feed circuit (Red wire) to A/C clutch relay. Go to step 14 .
  11. Replace A/C clutch relay. Go to step 14 .
  12. Check for poor ECM harness connections. Repair as necessary. Go to step 14 . If no problem is found, go to next step.
  13. Replace ECM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Go to next step.
  14. Turn ignition on, engine off. Using scan tool, command A/C clutch relay on and off. If A/C clutch relay turns on and off, A/C compressor control circuit is okay. If A/C clutch relay does not turn on and off, go to step 2 .

An intermittent condition may be caused by corrosion, misrouted wiring harness, rubbed through wire insulation, or a wire broken inside insulation. Perform visual inspection and check for continuity along suspect circuits. Repair as necessary.

When A/C is selected through A/C control panel, a 12-volt signal is supplied to A/C request input terminal of PCM. A/C clutch relay is controlled through PCM which also monitors A/C refrigerant pressure. If A/C refrigerant pressure, and engine operating conditions are within a specific calibrated acceptable range, the PCM will enable A/C clutch relay. This is accomplished by providing a ground path for A/C clutch relay coil with PCM. When A/C clutch relay is enabled, battery voltage is supplied to compressor clutch coil.

The PCM will enable A/C compressor clutch whenever engine is running and A/C has been requested, unless

  1. Throttle angle is greater than 90 percent.
  2. A/C head pressure is greater than 414 psi (29.1 kg/cm 2 ) with A/C refrigerant pressure sensor reading greater than 4.27 volts.
  3. A/C head pressure is less than 35 psi (2.5 kg/cm 2 ) with A/C refrigerant pressure sensor reading greater than .40 volts.
  4. Ignition voltage is less than 10.5 volts.
  5. Engine speed is greater than 4500 RPM for 5 seconds or at 5400 RPM for any amount of time.
  6. Engine coolant temperature is greater than 257°F (125°C).
  7. Intake air temperature is less than 41°F (5°C).
  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Connect scan tool to Data Link Connector (DLC). Check if any DTCs are set. If any DTCs are set, perform diagnosis for DTCs first. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no DTCs are set, go to next step.
  3. Ensure ambient air temperature is greater than 41°F (5°C), A/C pressure is greater than 35 psi (2.5 kg/cm 2 ) (.40 volt on scan tool), and coolant temperature is less than 250°F (121°C). Turn A/C off. Turn ignition on, engine off. Listen for engagement of A/C compressor clutch. If A/C compressor clutch engages, go to step 18 . If A/C compressor clutch does not engage, go to next step.
  4. With engine running at idle, select DEFROST or MAX mode. Observe A/C compressor clutch. If compressor clutch is engaged, problem may be intermittent. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) . If A/C compressor clutch is not engaged, go to next step.
  5. With DEFROST or MAX mode selected, monitor A/C REQUEST display on scan tool engine data list. If A/C REQUEST displays YES, go to step 9 . If A/C REQUEST does not display YES, go to next step.
  6. Turn ignition switch to OFF position. Disconnect PCM harness connectors. Turn ignition switch to ON position. With DEFROST or MAX mode selected, use a DVOM and measure voltage on A/C request circuit at PCM harness connector. See «WIRING DIAGRAMS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__wiring-diagrams) . If battery voltage is present, go to step 8 . If battery voltage is not present, go to next step.
  7. Check A/C request circuit for an open, short to ground, or poor connection at A/C control head/programmer. Repair as necessary. Go to step 29 . If no problem is found, diagnose A/C-heater controls. See appropriate MANUAL A/C-HEATER SYSTEMS article.
  8. Check A/C request circuit for a poor connection at PCM. Repair as necessary. Go to step 29 . If no problem is found, go to step 27 .
  9. Observe A/C refrigerant pressure display on scan tool. If pressure is 36-440 psi (2.5-30.9 kg/cm 2 ), go to step 12 . If pressure is not as specified, go to next step.
  10. Install A/C manifold gauge set. Observe high-side refrigerant pressure. If pressure is 36-440 psi (2.5-30 kg/cm 2 ), go to next step. If pressure is not as specified, charge A/C system. Go to step 29 .
  11. Turn ignition switch to OFF position. Disconnect A/C pressure sensor. Turn ignition switch to ON position. View A/C HIGH-SIDE display on scan tool engine data list. If scan tool displays A/C high-side pressure as 0 psi, go to step 28 . If scan tool does not display A/C high-side pressure as 0 psi, go to step 27 .
  12. Disconnect A/C clutch relay. Using a test light connected to ground, probe both ignition feed circuit terminals (Pink wires) at A/C clutch relay harness connector. If test light comes on at both terminals, go to next step. If test light does not come on at both terminals, go to step 23 .
  13. Connect a fused jumper wire between one ignition feed circuit (Pink wire) and A/C compressor clutch battery feed circuit (Dark Green wire) at A/C clutch relay harness connector. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, leave jumper wire in place and go to step 15 .
  14. Check for poor connections at A/C clutch relay. Repair as necessary. Go to step 29 . If no problem is found, go to step 24 .
  15. Disconnect A/C compressor clutch harness connector. Connect a test light between A/C compressor clutch battery feed circuit (Dark Green wire) and A/C compressor clutch ground circuit (Black wire). If test light comes on, go to next step. If test light does not come on, go to step 17 .
  16. Check for poor connections at A/C compressor clutch. Repair as necessary. Go to step 29 . If no problem is found, go to step 25 .
  17. Check for an open or short to ground in A/C compressor clutch battery feed circuit (Dark Green wire). Repair as necessary. Go to step 29 . If no problem is found, go to step 26 .
  18. Turn ignition on, A/C off. Observe A/C REQUEST display on scan tool. If A/C REQUEST displays YES, go to next step. If A/C REQUEST does not display YES, go to step 21 .
  19. Turn ignition switch to OFF position. Disconnect PCM harness connectors. Turn ignition on, A/C off. Using a DVOM, measure voltage between ground and A/C request circuit at PCM harness connector. If reading is near battery voltage, go to next step. If reading is not as specified, go to step 27 .
  20. Turn ignition switch to OFF position. Disconnect Body Function Controller (BFC). Turn ignition switch to ON position. Check A/C request circuit for a short to voltage. Repair as necessary. Go to step 29 . If no problem is found, diagnose A/C-heater controls. See appropriate MANUAL A/C-HEATER SYSTEMS article.
  21. Disconnect A/C clutch relay. Start engine and observe A/C compressor clutch. If A/C compressor clutch is engaged, go to next step. If A/C compressor clutch is not engaged, go to step 24 .
  22. Locate and repair short to voltage in A/C compressor clutch battery feed circuit (Dark Green wire). Go to step 29 .
  23. Repair open or short to ground in A/C clutch relay ignition feed circuit (Pink wire). Go to step 29 .
  24. Replace A/C clutch relay. Go to step 29 .
  25. Replace A/C compressor clutch coil. Go to step 29 .
  26. Locate and repair open in A/C compressor clutch ground circuit (Black wire). Go to step 29 .
  27. Replace PCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Go to step 29 .
  28. Replace A/C pressure sensor. Go to next step.
  29. Ensure ambient air temperature is greater than 41°F (5°C), A/C pressure is greater than 96°F (36°C), and coolant temperature is less than 250°F (121°C). Start engine and let idle. Turn A/C on. Listen for engagement of A/C compressor clutch. If A/C compressor clutch engages, system is okay at this time. If A/C compressor clutch does not engage, go to step 3 .

An intermittent condition may be caused by corrosion, misrouted wiring harness, rubbed through wire insulation or a wire broken inside insulation. Perform visual inspection and check for continuity along suspect circuits. Repair as necessary.

3.4L: ALERO & GRAND AM

Note. Body Function Controller (BFC) may also be referred to as a Body Control Module (BCM).

Powertrain Control Module (PCM) receives an A/C request signal from Body Control Module (BCM) over Class 2 serial data line. When A/C is requested, PCM provides a ground path to A/C clutch relay control circuit. When relay circuit is grounded, A/C clutch relay is energized. The PCM delays grounding relay circuit for .3 seconds. This allows PCM to adjust engine idle RPM for additional load.

The PCM will disengage A/C compressor clutch if one or more of the following conditions occur

  1. Throttle angle is greater than 90 percent.
  2. A/C head pressure is greater than 440 psi (31 kg/cm 2 ) with A/C refrigerant pressure sensor reading greater than 4.27 volts.
  3. A/C head pressure is less than 35 psi (2.5 kg/cm 2 ) with A/C refrigerant pressure sensor reading greater than .40 volts.
  4. Ignition voltage is less than 10.5 volts.
  5. Engine speed is greater than 4300 RPM for 5 seconds or at 5400 RPM for any amount of time.
  6. Engine coolant temperature is greater than 255°F (124°C).
  7. Intake air temperature is less than 41°F (5°C).
  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Check for any DTCs that may be set. If any DTCs are set, perform diagnosis for that DTC first. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no DTCs are set, go to appropriate MANUAL A/C-HEATER SYSTEMS article for diagnosis and repair.
  3. Ensure ambient air temperature is greater than 41°F (5°C), A/C pressure is greater than 35 psi (2.5 kg/cm 2 ) (.40 volt on scan tool), and coolant temperature is less than 250°F (121°C). Turn A/C off. Turn ignition on, engine off. Listen for engagement of A/C compressor clutch. If A/C compressor clutch engages, go to step 13 . If A/C compressor clutch does not engage, go to next step.
  4. Operate engine at 1000-1500 RPM. Turn A/C to on position. If A/C compressor clutch engages, go to «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) . If A/C compressor clutch does not engage, go to next step.
  5. Leave A/C in on position. Check A/C request function on scan tool. If scan tool indicates A/C REQUEST - YES, go to step 8 . If scan tool indicates A/C REQUEST - NO, go to next step.
  6. Monitor A/C pressure sensor on scan tool. If A/C pressure sensor indicates 0.4-4.2 volts, go to appropriate MANUAL A/C-HEATER SYSTEMS article. If A/C pressure sensor does not indicate 0.4-4.2 volts, go to next step.
  7. Install A/C manifold gauge set. Observe high-side refrigerant pressure. If pressure is 35-440 psi (2.5-30 kg/cm 2 ), go to DTC P0530 in appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If pressure is not as specified, charge A/C system.
  8. Check A/C BFC fuse (10-amp) located in underhood junction block. If fuse is blown, go to next step. If fuse is okay, go to step 10 .
  9. Remove A/C BFC fuse and A/C relay. Check for short to ground in battery feed to A/C relay, short to ground in battery feed to A/C compressor clutch (Dark Green wire), or a shorted diode. See «WIRING DIAGRAMS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__wiring-diagrams) . Repair as necessary and go to step 18 . If no problem was found, go to step 15 .
  10. Remove A/C relay. Connect a 10-amp fused jumper between battery positive voltage and A/C compressor clutch feed terminal. If A/C compressor clutch engages, go to step 12 . If A/C compressor clutch does not engage, go to next step.
  11. Check for open in battery feed circuit to A/C relay, open in battery feed circuit to A/C compressor clutch (Dark Green wire), open in A/C compressor clutch ground circuit, or poor connections at A/C compressor clutch connector. Repair as necessary and go to step 18 . If no problem was found, go to step 15 .
  12. Check for poor connections at A/C compressor relay. Repair as necessary and go to step 18 . If no problem was found, go to step 16 .
  13. Turn ignition switch to OFF position. Remove A/C relay. Turn ignition switch to ON position. If A/C compressor clutch is engaged, go to next step. If A/C compressor clutch is not engaged, go to step 16 .
  14. Disconnect A/C compressor clutch connector. If A/C compressor clutch is engaged, go to next step. If A/C compressor clutch is not engaged, go to step 17 .
  15. Replace A/C compressor. After repairs, go to step 18 .
  16. Replace A/C relay. After repairs, go to step 18 .
  17. Repair short to voltage in battery feed to circuit to A/C compressor clutch (Dark Green wire). After repairs, go to next step.
  18. Ensure ambient air temperature is greater than 41°F (5°C), A/C pressure is greater than 35 psi (2.5 kg/cm 2 ) (.40 volt on scan tool), and coolant temperature is less than 250°F (121°C). Start engine and operate at 1000-1500 RPM. Turn A/C to on position. Listen for engagement of A/C compressor clutch. Wait 5 minutes and turn A/C to off position. Listen for disengagement of A/C compressor clutch. If A/C compressor clutch engages and disengages, system is okay at this time. If A/C compressor clutch does not engage and disengage, go to step 3 .

An intermittent condition may be caused by corrosion, misrouted wiring harness, rubbed through wire insulation or a wire broken inside insulation. Perform visual inspection and check for continuity along suspect circuits. Repair as necessary. If circuits are okay, check conditions listed under DESCRIPTION .

Description (A/C Request Circuit - Manual HVAC System)

When A/C is requested from the Heating, Ventilation and Air Conditioning (HVAC) control head, the A/C system sends a 12 volt signal from the HVAC control head to the PCM. The PCM then grounds the A/C relay circuit to energize the relay to allow current to flow to the A/C compressor clutch. The PCM will de-energize the A/C relay if one or more of the following conditions occur

  1. High coolant temperature.
  2. Low A/C system pressures.
  3. High A/C system pressures.
  4. Wide Open Throttle (WOT) operation.
  5. High engine RPM.
  6. Specific DTCs are set in the PCM.

When A/C request is detected by the PCM, the cooling fans will be turned on after A/C pressures are high enough. For diagnosis and repair, see A/C REQUEST CIRCUIT DIAGNOSIS (MANUAL HVAC) .

Description (A/C Request Circuit - Automatic HVAC)

When A/C is requested from the Heating, Ventilation and Air Conditioning (HVAC) control head, the A/C system sends a Class 2 serial data message from the HVAC control head to the PCM. The PCM then grounds the A/C relay circuit to energize the relay to allow current to flow to the A/C compressor clutch. The PCM will de-energize the A/C relay if one or more of the following conditions occur

  1. High coolant temperature.
  2. Low A/C system pressures.
  3. High A/C system pressures.
  4. Wide Open Throttle (WOT) operation.
  5. High engine RPM.
  6. Specific DTCs are set in the PCM.

When A/C request is detected by the PCM, the cooling fans will be turned on after A/C pressures are high enough. For diagnosis and repair, see A/C REQUEST CIRCUIT DIAGNOSIS (AUTOMATIC HVAC) .

A/C Request Circuit Diagnosis (Manual HVAC)

  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Check for any DTCs that may be set. If any DTCs are set, perform diagnosis for that DTC first. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no DTCs are set, go to go to next step.
  3. Idle engine with A/C in off position. Using scan tool, check A/C request function. If scan tool indicates A/C REQUEST - YES, go to step 8 . If scan tool indicates A/C REQUEST - NO, go to next step.
  4. Turn A/C to ON position. If scan tool indicates A/C REQUEST - YES, system is operating properly at this time. If scan tool indicates A/C REQUEST - NO, go to next step.
  5. Turn ignition switch to OFF position. Disconnect PCM connector C2. Turn ignition switch to ON position. Use DVOM to measure voltage along A/C request circuit between connector C2 terminal No. 22 (Dark Green/White wire) and ground. See «WIRING DIAGRAMS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__wiring-diagrams) . Turn A/C on. If battery voltage is indicated, go to step 10 . If battery voltage is not indicated, go to next step.
  6. Turn ignition switch to OFF position. Disconnect HVAC control head connector. Use DVOM to check for continuity in A/C request circuit between HVAC control head and PCM. If continuity is indicated, go to next step. If continuity is not indicated, go to step 11 .
  7. Connect a test light to battery voltage and probe A/C request circuit at PCM connector. If test light comes on, go to step 12 . If test light does not come on, go to step 9 .
  8. Check for short to voltage in A/C request circuit. Repair as necessary and go to step 14 . If no problem was found, go to next step.
  9. Replace HVAC control head. See MANUAL A/C-HEATER - INTRIGUE article. After repairs, go to step 14 .
  10. Check for poor connections at PCM connector C2. Repair as necessary and go to step 14 . If no problem was found, go to step 13 .
  11. Repair open or high resistance in A/C request circuit. Go to step 14 .
  12. Repair short to voltage in A/C request circuit. Go to step 14 .
  13. Replace PCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. After repairs, go to next step.
  14. Idle engine with A/C in off position. Check A/C request function on scan tool. Cycle A/C on and off a few times, allowing the system to stabilize between cycles. If scan tool indicates A/C REQUEST - YES with the A/C on and NO with the A/C off, system is operating properly at this time. Go to «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) . If scan tool display is not as specified, go to step 2 .

An intermittent condition may be caused by corrosion, misrouted wiring harness, rubbed through wire insulation or a wire broken inside insulation. Perform visual inspection and check for continuity along suspect circuits. Repair as necessary. If circuits are okay, check conditions listed under DESCRIPTION (A/C REQUEST CIRCUIT - MANUAL HVAC SYSTEM) .

A/C Request Circuit Diagnosis (Automatic HVAC)

If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to AUTOMATIC A/C-HEATER SYSTEMS - INTRIGUE article.

When A/C mode is selected, a 12-volt signal is supplied to the A/C request input terminal of PCM. A/C clutch relay is controlled through PCM which also monitors A/C refrigerant pressure. If A/C refrigerant pressure and engine operating conditions are within a specific calibrated acceptable range, PCM will enable A/C clutch relay. This is done by providing a ground path for A/C clutch relay coil through PCM. When A/C clutch relay is enabled, battery voltage is supplied to compressor clutch coil.

The PCM will enable compressor clutch whenever engine is running and A/C has been requested, unless

  1. Throttle angle is greater than 90 percent.
  2. A/C head pressure, is greater than 414 psi (29.1 kg/cm 2 ) with A/C refrigerant pressure sensor reading greater than 4.27 volts.
  3. A/C head pressure is less than 34 psi (2.5 kg/cm 2 ) with A/C refrigerant pressure sensor less than 0.35 volts.
  4. Ignition voltage is less than 10 volts.
  5. Engine speed is greater than 4225 RPM for longer than 5 seconds.
  6. Engine speed is greater than 5280 RPM for any amount of time.
  7. Engine coolant temperature is greater than 257°F (125°C).
  8. Intake air temperature is less than 32°F (0°C).
  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Check for any DTCs that may be set. If any DTCs are set, perform diagnosis for that DTC first. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no DTCs are set, go to appropriate MANUAL A/C-HEATER SYSTEMS or AUTOMATIC A/C-HEATER SYSTEMS article for diagnosis and repair.

When A/C mode is selected, a 12-volt signal is supplied to the A/C request input terminal of PCM. The A/C clutch relay is controlled through PCM which also monitors A/C refrigerant pressure. If A/C refrigerant pressure and engine operating conditions are within an acceptable range, PCM will enable A/C clutch relay. This is done by providing a ground path for A/C clutch relay coil through PCM. When A/C clutch relay is enabled, battery voltage is supplied to compressor clutch coil.

The PCM will enable compressor clutch whenever engine is running and A/C has been requested, unless

  1. Throttle angle is greater than 90 percent.
  2. A/C head pressure is greater than 414 psi (29.1 kg/cm 2 ).
  3. A/C head pressure is less than 34 psi (2.5 kg/cm 2 ).
  4. Ignition voltage is less than 10.5 volts.
  5. Engine speed is greater than 5440 RPM.
  6. Engine coolant temperature is greater than 257°F (125°C).
  7. Intake air temperature is less than 41°F (5°C).
  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Check for any DTCs that may be set. If any DTCs are set, perform diagnosis for that DTC first. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no DTCs are set, go to next step.
  3. Ensure intake air temperature is greater than 48°F (9°C). Ensure engine coolant temperature is less than 246°F (119°C). Turn A/C off. Start engine and let idle. Observe A/C compressor clutch. If A/C compressor clutch is engaged, go to step 21 . If A/C compressor clutch is not engaged, go to next step.
  4. Run engine at 1000-1500 RPM. Select A/C mode on A/C control panel. Observe A/C compressor clutch. If A/C compressor clutch is engaged, system is operating properly at this time. Problem may be intermittent. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) . If A/C compressor clutch is not engaged, go to next step.
  5. With A/C mode still selected, observe A/C REQUEST display on scan tool. If A/C REQUEST displays YES, go to step 9 . If A/C REQUEST does not display YES, go to next step.
  6. Turn ignition switch to OFF position. Disconnect PCM harness connectors. Turn ignition switch to ON position. With A/C mode still selected, use a DVOM and measure voltage on A/C request circuit (Light Green wire or Dark Green/White wire) at PCM harness connector. See «WIRING DIAGRAMS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__wiring-diagrams) . If reading is near battery voltage, go to step 8 . If reading is not as specified, go to next step.
  7. Check A/C request circuit (Light Green wire or Dark Green/White wire) for an open, short to ground, or poor connection at A/C control panel. Repair as necessary. Go to step 37 . If no problem is found, diagnose A/C-heater controls. See MANUAL A/C-HEATER SYSTEMS - CAMARO & FIREBIRD article.
  8. Check A/C request circuit (Dark Green/White wire) for a poor connection at PCM. Repair as necessary. Go to step 37 . If no problem is found, go to step 35 .
  9. Observe A/C pressure sensor display on scan tool. If reading is .35-4.27 volts, go to step 12 . If reading is not as specified, go to next step.
  10. Connect A/C manifold gauge set. Observe high-side refrigerant pressure on gauge. If high-side refrigerant pressure is 34-414 psi (2.3-29 kg/cm 2 ), go to next step. If high-side refrigerant pressure is not as specified, charge A/C system.
  11. Turn ignition switch to OFF position. Disconnect PCM and A/C pressure sensor harness connectors. Using a DVOM, measure resistance of the following circuits between PCM and A/C pressure sensor harness connectors: A/C pressure sensor signal circuit. 5-volt reference "B" circuit. Sensor ground circuit. If any resistance is greater than 5 ohms, locate and repair cause of high resistance in circuit as necessary, then go to step 37 . If no resistance is greater than 5 ohms, go to step 18 .
  12. Disconnect A/C clutch relay harness connector. Using a test light connected to ground, probe ignition feed circuits (Pink wires) at A/C clutch relay harness connector. If test light comes on, go to next step. If test light does not come on, go to step 31 .
  13. Connect a fused jumper wire between ignition feed circuit and A/C compressor clutch battery feed circuit (Dark Green wire) at A/C clutch relay harness connector. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, leave jumper wire in place and go to step 15 .
  14. Check for poor connections at A/C clutch relay. Repair as necessary. Go to step 37 . If no problem is found, go to step 32 .
  15. With jumper wire still connected, disconnect A/C compressor clutch harness connector. Connect a test light between A/C compressor clutch battery feed circuit (Dark Green wire) and A/C compressor clutch ground circuit (Black wire). If test light comes on, go to next step. If test light does not come on, go to step 17 .
  16. Check for poor connections at A/C compressor clutch. Repair as necessary. Go to step 37 . If no problem is found, go to step 33 .
  17. Check for an open or short to ground in A/C compressor clutch battery feed circuit (Dark Green wire). Repair as necessary. Go to step 37 . If no problem is found, go to step 34 .
  18. Leave PCM and A/C pressure sensor harness connectors disconnected. Turn ignition switch to ON position. Using a DVOM, measure voltage between A/C pressure sensor signal circuit (Red/Black wire) and ground. If reading is near zero volts, go to next step. If reading is not as specified, go to step 20 .
  19. Check for the following conditions: 5-volt reference "B" circuit for a poor connection at PCM. 5-volt reference "B" circuit (Gray wire) for a poor connection at A/C pressure sensor. A/C pressure sensor signal circuit for a poor connection at PCM. A/C pressure sensor signal circuit for a poor connection at A/C pressure sensor. Sensor ground circuit for a poor connection at A/C pressure sensor. Repair as necessary and go to step 37 . If no problem is found, go to step 36 .
  20. Locate and repair short to voltage in A/C pressure signal circuit (Red/Black wire). Go to step 37 .
  21. Turn ignition on, A/C off. Observe A/C REQUEST on scan tool display. If A/C REQUEST displays YES, go to next step. If A/C REQUEST does not display YES, go to step 24 .
  22. Turn ignition switch to OFF position. Disconnect PCM harness connectors. Turn ignition on, A/C off. Using a DVOM, measure voltage between ground and A/C request circuit (Light Green wire or Dark Green/White wire) at PCM harness connector. If reading is near battery voltage, go to next step. If reading is not as specified, go to step 35 .
  23. Turn ignition switch to OFF position. Disconnect A/C control head/programmer harness connectors. Turn ignition switch to ON position. Using a DVOM, check A/C request circuit for a short to voltage. Repair as necessary. Go to step 37 . If no problem is found, diagnose A/C-heater controls. See MANUAL A/C-HEATER SYSTEMS - CAMARO & FIREBIRD article.
  24. Disconnect A/C clutch relay. Start engine and observe A/C compressor clutch. If A/C compressor clutch is engaged, go to step 29 . If A/C compressor clutch is not engaged, go to next step.
  25. Using a test light connected to ground, probe A/C compressor clutch ignition feed circuit (Dark Green wire) at A/C relay harness connector. If test light comes on, go to step 27 . If test light does not come on, go to next step.
  26. Replace A/C clutch relay. Go to step 37 .
  27. Turn ignition switch to OFF position. Disconnect PCM harness connectors. Using a test light connected to battery positive, probe A/C clutch relay control circuit (Dark Green/White wire) at PCM harness connector. If test light comes on, go to next step. If test light does not come on, go to step 35 .
  28. Repair short to ground in A/C clutch relay control circuit (Dark Green/White wire). Go to step 37 .
  29. Turn ignition switch to OFF position. Disconnect A/C compressor clutch harness connector. Start engine and observe compressor clutch. If A/C compressor clutch is engaged, go to step 33 . If A/C compressor clutch is not engaged, go to next step.
  30. Locate and repair short to voltage in A/C compressor clutch battery feed circuit (Dark Green wire). Go to step 37 .
  31. Repair open or short to ground in appropriate ignition feed circuit (Pink wire) to A/C clutch relay. Go to step 37 .
  32. Replace A/C clutch relay. Go to step 37 .
  33. Repair A/C compressor clutch or replace A/C compressor clutch coil. Go to step 37 .
  34. Locate and repair open in A/C compressor clutch ground circuit (Black wire). Go to step 37 .
  35. Replace PCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Go to step 37 .
  36. Replace A/C pressure sensor. Go to next step.
  37. Ensure intake air temperature is greater than 48°F (9°C). Ensure engine coolant temperature is less than 246°F (119°C). With A/C off, start engine and let idle. Observe A/C compressor clutch. If A/C compressor clutch is engaged, go to step 21 . If A/C compressor clutch is not engaged, go to next step.
  38. Run engine at 1000-1500 RPM. Select A/C mode on control panel. Observe A/C compressor clutch. If A/C compressor clutch is engaged, system is okay. If A/C compressor clutch is not engaged, go to step 5 .

Check for poor harness connections at PCM and A/C control head. Inspect for corrosion, backed-out terminal pins, and broken wires inside insulation. Check for damaged wire harness. If harness and connections are okay, disconnect PCM harness connectors. Connect a DVOM between ground and A/C clutch relay control circuit at PCM harness connector. Turn ignition switch to ON position. Observe DVOM while wiggling harness and connectors. A change in voltage indicates location of fault.

An A/C refrigerant pressure less than 35 psi (2.5 kg/cm 2 ), or greater than 414 psi (29.1 kg/cm 2 ) will cause PCM to disable A/C compressor clutch. With engine running and A/C on, use scan tool to monitor A/C high-side system pressure for 2 minutes. If pressure goes out of range, diagnose A/C-heater system. See MANUAL A/C-HEATER SYSTEMS - CAMARO & FIREBIRD article.

When A/C mode is selected, a 12-volt signal is supplied to the A/C request input terminal of PCM. The A/C clutch relay is controlled through PCM, which also monitors A/C refrigerant pressure. If A/C refrigerant pressure and engine operating conditions are within an acceptable range, the PCM will enable A/C clutch relay by providing a ground path for the A/C clutch relay. When A/C clutch relay is enabled, battery voltage is supplied to A/C compressor clutch coil.

The PCM will enable A/C compressor clutch whenever engine is running and A/C has been requested, unless

  1. Throttle angle is greater than 96 percent.
  2. A/C head pressure is greater than 440 psi (30.9 kg/cm 2 ).
  3. A/C head pressure is less than 32 psi (2.2 kg/cm 2 ).
  4. Ignition voltage is less than 10 volts.
  5. Engine speed is greater than 4392 RPM for one second on Grand Prix; or greater than 4400 RPM for any length of time on Grand Prix, Lumina and Monte Carlo.
  6. Engine coolant temperature is greater than 255°F (124°C).
  7. Intake air temperature is less than 41°F (5°C).
  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Install scan tool. Check if any DTCs are set. If any DTCs are set, perform diagnosis for DTCs first. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no DTCs are set, go to next step.
  3. Ensure ambient air temperature is greater than 41°F (5°C), A/C pressure is greater than 32 psi (2.2 kg/cm 2 ), and coolant temperature is less than 250°F (121°C). Turn A/C off. Turn ignition on, engine off. Listen for engagement of A/C compressor clutch. If A/C compressor clutch engages, go to step 21 . If A/C compressor clutch does not engage, go to next step.
  4. With engine running at idle, select A/C mode on A/C control panel. Observe A/C compressor clutch. If A/C compressor clutch is engaged, problem may be intermittent. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) . If A/C compressor clutch is not engaged, go to next step.
  5. With A/C mode selected, monitor A/C REQUEST display on scan tool engine data list. If A/C REQUEST displays YES, go to step 9 . If A/C REQUEST does not display YES, go to next step.
  6. Turn ignition switch to OFF position. Disconnect PCM harness connectors. Turn ignition switch to ON position. With A/C mode selected, use a DVOM and measure voltage on A/C request circuit at PCM harness connector. See «WIRING DIAGRAMS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__wiring-diagrams) . If battery voltage is present, go to step 8 . If battery voltage is not present, go to next step.
  7. Check A/C request circuit for an open, short to ground or poor connection at A/C control head/programmer. Repair as necessary. Go to step 42 . If no problem is found, diagnose A/C controls. See appropriate MANUAL A/C-HEATER SYSTEMS article.
  8. Check A/C request circuit for a poor connection at PCM. Repair as necessary. Go to step 42 . If no problem is found, go to step 40 .
  9. Observe A/C refrigerant pressure display on scan tool. If pressure is 32-440 psi (2.2-30.9 kg/cm 2 ), go to step 12 . If pressure is not as specified, go to next step.
  10. Install A/C manifold gauge set. Observe high-side refrigerant pressure. If pressure is 32-440 psi (2.2-30 kg/cm 2 ), go to next step. If pressure is not as specified, charge A/C system.
  11. Turn ignition switch to OFF position. Disconnect A/C pressure sensor. Turn ignition switch to ON position. View A/C HIGH-SIDE display on scan tool engine data list. If scan tool displays A/C HIGH-SIDE as 0 psi, go to step 41 . If scan tool does not display A/C HIGH-SIDE as 0 psi, go to step 40 .
  12. Check A/C CLU/ABS IGN fuse (10-amp) on Lumina and Monte Carlo, or A/C CONT fuse (10-amp) on Grand Prix, in underhood fuse/relay box. If fuse is blown, go to next. If fuse is okay, go to step 17 .
  13. Turn ignition switch to OFF position. Remove A/C clutch fuse and A/C clutch relay. Using a test light connected to battery voltage, probe both ignition feed circuits at A/C clutch relay connector. If test light comes on, go to step 31 . If test light does not come on, go to next step.
  14. Leave A/C clutch relay disconnected. Disconnect A/C compressor clutch harness connector. Using a test light connected to battery voltage, probe A/C compressor clutch battery feed circuit (Dark Green wire) at A/C clutch relay connector. If test light comes on, go to step 32 . If test light does not come on, go to next step.
  15. Check for an open A/C compressor clutch diode. Repair as necessary. Go to step 42 . If no problem is found, go to next step.
  16. Turn ignition switch to OFF position. Reconnect A/C clutch relay. Disconnect PCM harness connectors. Turn ignition switch to ON position. Using a DVOM set to 10-amp scale, measure current draw between ground and A/C clutch relay control circuit (Dark Green/White wire) at PCM harness connector for at least 2 minutes. If current draw is 0.5-1.5 amps, go to step 38 . If current draw is not as specified, go to step 39 .
  17. Turn ignition switch to OFF position. Remove A/C clutch relay. Turn ignition switch to ON position. Using a test light connected to ground, probe A/C clutch relay ignition feed circuits in A/C clutch relay connector. If test light comes on, go to next step. If test light does not come on, go to step 33 .
  18. Leave A/C clutch relay disconnected. Connect a 10-amp fused jumper wire between A/C clutch relay ignition feed circuit and A/C compressor clutch battery feed circuit in A/C clutch relay connector. If A/C compressor clutch engages, go to step 21 . If A/C compressor clutch does not engage, go to next step.
  19. Leave jumper wire connected. Disconnect A/C compressor clutch harness connector. Using a test light connected to ground, probe A/C compressor clutch battery feed circuit (Dark Green wire) at A/C compressor clutch connector. If test light comes on, go to next step. If test light does not come on, go to step 34 .
  20. Using a test light connected to battery voltage, probe A/C compressor clutch ground circuit (Black wire) at A/C compressor clutch harness connector. If test light comes on, go to step 38 . If test light does not come on, go to step 35 .
  21. Leave A/C clutch relay disconnected. Connect a test light between A/C clutch relay ignition feed and control circuits at A/C clutch relay connector. Using scan tool in OUTPUT FUNCTIONS mode, cycle A/C clutch relay on and off. If test light flashes on and off, go to next step. If test light does not flash on and off, go to step 23 .
  22. Check A/C relay for poor connections. Repair as necessary. Go to step 42 . If no problem is found, go to step 39 .
  23. Check for an open in A/C clutch relay control circuit or poor terminal connection at PCM. Repair as necessary. Go to step 42 . If no problem is found, go to step 40 .
  24. Turn ignition on, A/C off. Observe A/C REQUEST display on scan tool. If A/C REQUEST displays YES, go to next step. If A/C REQUEST does not display YES, go to step 27 .
  25. Turn ignition switch to OFF position. Disconnect PCM harness connectors. Turn ignition on, A/C off. Using a DVOM, measure voltage between ground and A/C request circuit at PCM harness connector. If reading is near battery voltage, go to next step. If reading is not as specified, go to step 27 .
  26. Turn ignition switch to OFF position. Disconnect A/C control head harness connector. Turn ignition switch to ON position. Using a DVOM, check A/C request circuit for a short to voltage. Repair as necessary. Go to step 42 . If no problem is found, diagnose A/C-heater controls. See appropriate MANUAL A/C-HEATER SYSTEMS article.
  27. Leave A/C off. Disconnect A/C clutch relay. Start engine and observe A/C compressor clutch. If A/C compressor clutch is engaged, go to next step. If A/C compressor clutch is not engaged, go to step 29 .
  28. Turn ignition switch to OFF position. Disconnect A/C compressor clutch harness connector. Start engine. If A/C compressor clutch engages, go to step 38 . If A/C compressor clutch does not engage, go to step 36 .
  29. Turn ignition switch to OFF position. Leave A/C clutch relay disconnected with A/C off. Using a test light connected to battery voltage, probe A/C clutch relay control circuit at A/C clutch relay connector. Turn ignition switch to ON position. If test light comes on, leave test light connected and go to next step. If test light does not come on, go to step 39 .
  30. Disconnect PCM harness connectors. Turn ignition switch to ON position. Probe A/C clutch relay control circuit in A/C clutch relay connector. If test light comes on, go to step 37 . If test light does not come on, go to step 40 .
  31. Locate and repair short to ground in ignition feed circuits to A/C clutch relay. Go to step 42 .
  32. Locate and repair short to ground in A/C compressor clutch battery feed circuit (Dark Green wire) and/or shorted A/C compressor clutch diode. Go to step 42 .
  33. Locate and repair open in ignition feed circuits to A/C clutch relay. Go to step 42 .
  34. Locate and repair open in A/C compressor clutch battery feed circuit (Dark Green wire). Go to step 42 .
  35. Locate and repair open in A/C compressor clutch ground circuit (Black wire). Go to step 42 .
  36. Locate and repair short to voltage in A/C compressor clutch battery feed circuit (Dark Green wire). Go to step 42 .
  37. Locate and repair short to ground in A/C clutch relay control circuit. Go to step 42 .
  38. Replace A/C compressor clutch coil. Go to step 42 .
  39. Replace A/C clutch relay. Go to step 42 .
  40. Replace PCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Go to next step. Go to step 42 .
  41. Replace A/C pressure sensor. Go to next step.
  42. Ensure ambient air temperature is greater than 41°F (5°C), A/C pressure is greater than 32 psi (2.2 kg/cm 2 ), and coolant temperature is less than 250°F (121°C). Start engine and let idle. Turn A/C on. Listen for engagement of A/C compressor clutch. If A/C compressor clutch engages, system is okay. If A/C compressor clutch does not engage, go to step 3 .

Check for poor harness connections at PCM. Inspect for corrosion, backed-out terminal pins, or broken wires inside insulation. Check for damaged wire harness. If harness and connections are okay, disconnect PCM harness connectors. Connect a DVOM between ground and A/C clutch relay control circuit at PCM harness connector. Turn ignition switch to ON position. Observe DVOM while wiggling harness and connectors. A change in voltage indicates location of fault.

An A/C refrigerant pressure less than 32 psi (2.2 kg/cm 2 ), or greater than 440 psi (30.9 kg/cm 2 ) will cause PCM to disable A/C compressor clutch. With engine running and A/C on, use scan tool to monitor A/C high-side system pressure for 2 minutes. If pressure goes out of range, diagnose A/C-heater system. See appropriate MANUAL A/C-HEATER SYSTEMS article.

When A/C mode is selected, a 12-volt signal is supplied to the A/C request input terminal of PCM. The A/C clutch relay is controlled through Powertrain Control Module (PCM), which also monitors A/C refrigerant pressure. If A/C refrigerant pressure and engine operating conditions are within an acceptable range, the PCM will enable A/C clutch relay by providing a ground path for A/C clutch relay. When A/C clutch relay is enabled, battery voltage is supplied to A/C compressor clutch coil.

The PCM will enable A/C compressor clutch whenever engine is running and A/C has been requested, unless

  1. Throttle angle is greater than 96 percent.
  2. A/C head pressure is greater than 440 psi (30.9 kg/cm 2 ).
  3. A/C head pressure is less than 32-35 psi (2.3-2.5 kg/cm 2 ).
  4. Ignition 1 voltage is less than 9.5 volts.
  5. Engine speed is greater than 4392 RPM for more than one second on VIN K engine, or greater than 4392 RPM for any amount of time on VIN 1 engine.
  6. Engine speed is greater than 4400 RPM for any amount of time.
  7. Engine coolant temperature is greater than 255°F (124°C).
  8. Intake air temperature is less than 41°F (5°C).
  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Connect scan tool to Data Link Connector (DLC). Check if any DTCs are set. If any DTCs are set, perform diagnosis for DTCs first. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no DTCs are set, go to next step.
  3. Ensure ambient air temperature is greater than 41°F (5°C), A/C pressure is greater than about 35 psi (2.5 kg/cm 2 ), and coolant temperature is less than 250°F (121°C). Turn A/C off. Turn ignition on, engine off. Listen for engagement of A/C compressor clutch. If A/C compressor clutch engages, go to step 25 . If A/C compressor clutch does not engage, go to next step.
  4. With engine running at 1000-1500 RPM, select A/C mode on A/C control panel. Observe A/C compressor clutch. If A/C compressor clutch is engaged, problem may be intermittent. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) . If A/C compressor clutch is not engaged, go to next step.
  5. With A/C mode selected, monitor A/C REQUEST display on scan tool engine data list. If A/C REQUEST displays YES, go to step 12 . If A/C REQUEST does not display YES, go to next step.
  6. Using scan tool, observe A/C pressure sensor voltage. If reading is .4-4.6 volts, diagnose A/C-heater system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article. If reading is not as specified, go to next step.
  7. Connect A/C manifold gauge set. Observe high-side refrigerant pressure. If pressure is 35-440 psi (2.5-30 kg/cm 2 ), go to next step. If pressure is not as specified, charge A/C system.
  8. Turn ignition switch to OFF position. Disconnect PCM and A/C pressure sensor harness connectors. Using a DVOM, measure resistance of the following circuits between PCM and A/C pressure sensor harness connectors: A/C pressure sensor signal circuit (Red/Black wire). 5-volt reference "B" circuit (Gray wire). Sensor ground circuit (Black wire). If resistance of any circuit is greater than 5 ohms, repair high resistance in appropriate circuit. Go to step 44 . If no problem is found, go to next step.
  9. Leave PCM and A/C pressure sensor harness connectors disconnected. Turn ignition switch to ON position. Using a DVOM, measure voltage between ground and A/C pressure sensor signal circuit (Red/Black wire) at A/C pressure sensor harness connector. If reading is near zero volts, go to next step. If reading is not as specified, go to step 11 .
  10. Check 5-volt reference "B" circuit (Gray wire) and A/C pressure sensor signal circuit (Red/Black wire) for poor connections at PCM. Also, check 5-volt reference "B" circuit (Gray wire) and A/C pressure sensor ground circuit (Black wire) for poor connections at A/C pressure sensor. Repair as necessary. Go to step 44 . If no problem is found, go to step 41 .
  11. Locate and repair short to voltage in A/C pressure sensor signal circuit (Red/Black wire). Repair as necessary. Go to step 44 .
  12. Check A/C clutch fuse (10-amp) located in underhood fuse/relay box. If fuse is blown, go to next step. If fuse is okay, go to step 15 .
  13. Turn ignition switch to OFF position. Remove A/C clutch fuse (10-amp) located in underhood fuse/relay box. Remove A/C clutch relay. Using a test light connected to battery voltage, probe cavity No. 30 of A/C clutch relay connector. If test light comes on, go to step 30 . If test light does not come on, go to next step.
  14. Leave A/C clutch relay disconnected. Disconnect A/C compressor clutch harness connector. Using a test light connected to battery voltage, probe cavity No. 87 of A/C clutch relay connector. If test light comes on, go to step 31 . If test light does not come on, go to step 40 .
  15. Turn ignition switch to OFF position. Remove A/C clutch relay. Using a test light connected to ground, probe cavity No. 30 of A/C clutch relay connector. If test light comes on, go to next step. If test light does not come on, go to step 33 .
  16. Leave A/C clutch relay disconnected. Connect a fused jumper wire between cavities No. 30 and No. 87 of A/C clutch relay connector. If A/C compressor clutch engages, go to step 20 . If A/C compressor clutch does not engage, leave jumper wire connected and go to next step.
  17. Disconnect A/C compressor clutch harness connector. Using a test light connected to ground, probe Dark Green wire at A/C compressor clutch harness connector. If test light comes on, go to next step. If test light does not come on, go to step 34 .
  18. Using a test light connected to battery voltage, probe Black wire at A/C compressor clutch harness connector. If test light comes on, go to next step. If test light does not come on, go to step 34 .
  19. Check for poor connections at A/C compressor clutch harness connector. Repair as necessary. Go to step 44 . If no problem is found, go to step 40 .
  20. Turn ignition switch off and back on. Using a test light connected to ground, probe cavity No. 85 of A/C clutch relay connector. If test light comes on, go to next step. If test light does not come on, go to step 36 .
  21. Connect a test light between cavities No. 85 and No. 86 of A/C clutch relay connector. Ensure ignition is on. Using scan tool, command A/C clutch relay on and off. If test light flashes on and off, go to next step. If test light does not flash on and off, go to step 23 .
  22. Check A/C clutch relay for poor connections. Repair as necessary. Go to step 44 . If no problem is found, go to step 42 .
  23. Turn ignition switch to OFF position. Disconnect PCM harness connectors. Turn ignition switch to ON position. Using a test light connected to ground, probe A/C clutch relay control circuit (Dark Green/White wire). If test light comes on, go to step 37 . If test light does not come on, go to next step.
  24. Check for an open in A/C clutch relay control circuit (Dark Green/White wire). Also, check for poor connections at PCM. Repair as necessary. Go to step 44 . If no problem is found, go to step 43 .
  25. Ensure A/C is off. Observe A/C REQUEST display on scan tool. If A/C REQUEST displays YES, diagnose A/C-heater controls. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article. If A/C REQUEST does not display YES, go to next step.
  26. Disconnect A/C clutch relay. Start engine and let idle. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, go to step 29 .
  27. Turn ignition switch to OFF position. Disconnect A/C compressor clutch harness connector. Start engine and let idle. If A/C compressor clutch engages, go to step 40 . If A/C compressor clutch does not engage, go to next step.
  28. Locate and repair short to voltage in A/C compressor clutch battery feed circuit (Dark/Green wire). Go to step 44 .
  29. Using a test light connected to ground, probe A/C clutch relay control circuit (Dark Green/White wire) at A/C clutch relay connector. If test light comes on, go to next step. If test light does not come on, go to step 42 .
  30. Turn ignition switch to OFF position. Disconnect PCM harness connectors. Using a test light connected to battery voltage, probe A/C clutch relay control circuit (Dark Green/White wire) at A/C clutch relay connector. If test light comes on, go to step 39 . If test light does not come on, go to step 43 .
  31. Locate and repair short to ground in battery feed circuit to cavity No. 30 in A/C clutch relay connector. Go to step 44 .
  32. Locate and repair short to ground in A/C compressor clutch battery feed circuit (Dark Green wire) and/or shorted A/C compressor clutch diode. Go to step 44 .
  33. Locate and repair open in battery feed circuit to cavity No. 30 in A/C clutch relay connector. Go to step 44 .
  34. Locate and repair open in battery feed circuit (Dark Green wire) to A/C compressor clutch. Go to step 44 .
  35. Locate and repair open in A/C compressor clutch ground circuit (Black wire). Go to step 44 .
  36. Locate and repair open in battery feed circuit to cavity No. 85 in A/C clutch relay connector. Go to step 44 .
  37. Locate and repair short to voltage in A/C clutch relay control circuit (Dark Green/White wire). Go to step 44
  38. Locate and repair short to voltage in A/C compressor clutch battery feed circuit (Dark Green wire). Go to step 44 .
  39. Locate and repair short to ground in A/C clutch relay control circuit (Dark Green/White wire). Go to step 44 .
  40. Replace A/C compressor clutch coil. Go to step 44 .
  41. Replace A/C pressure sensor. Go to step 44 .
  42. Replace A/C clutch relay. Go to step 44 .
  43. Replace PCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Go to next step.
  44. Ensure ambient air temperature is greater than 41°F (5°C), A/C pressure is greater than about 35 psi (2.5 kg/cm 2 ), and coolant temperature is less than 250°F (121°C). Start engine and let idle. Turn A/C on. Listen for engagement of A/C compressor clutch. If A/C compressor clutch engages, system is okay at this time. If A/C compressor clutch does not engage, go to step 3 .

Check for poor harness connections at PCM. Inspect for corrosion, backed-out terminal pins, and broken wires inside insulation. Check for damaged wire harness. If harness and connections are okay, disconnect PCM harness connectors. Connect a DVOM between ground and A/C clutch relay control circuit at PCM harness connector. Turn ignition switch to ON position. Observe DVOM while wiggling harness and connectors. A change in voltage indicates location of fault.

An A/C refrigerant pressure less than about 35 psi (2.5 kg/cm 2 ), or greater than 440 psi (30.9 kg/cm 2 ) will cause PCM to disable A/C compressor clutch. With engine running and A/C on, use scan tool to monitor A/C high-side system pressure for 2 minutes. If pressure goes out of range, diagnose A/C-heater system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article.

System consists of A/C control head, A/C refrigerant high and low pressure switches, A/C high and low temperature sensors, control relay, A/C compressor clutch, and PCM.

When A/C control head is placed in A/C mode, a request signal is sent to PCM. The PCM will then energize A/C clutch relay, unless abnormally high or low A/C pressure is detected by A/C pressure switches. The PCM also monitors A/C low temperature sensors to cycle compressor clutch on and off. If PCM detects an A/C evaporator temperature less than 36°F (2°C), PCM will not allow A/C compressor clutch to engage. The PCM will also energize cooling fans when A/C is requested.

  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Check if any DTCs are set. If any DTCs are set, perform diagnosis for DTCs first. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no DTCs are set, go to next step.
  3. Ensure ambient temperature is greater than -10°F (-23°C). With A/C off, start engine and let idle. Observe A/C compressor clutch. If A/C compressor clutch is engaged, go to step 10 . If A/C compressor clutch is not engaged, go to next step.
  4. With engine idling and A/C on for more than 30 seconds, check A/C compressor clutch. If A/C compressor clutch is engaged, system is okay at this time. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) . If A/C compressor clutch is not engaged, go to next step.
  5. Turn ignition switch to OFF position. Connect scan tool. Turn ignition switch to ON position. With A/C still on, observe A/C clutch relay control circuit status on scan tool. If scan tool displays OKAY, go to next step. If scan tool does not display OKAY, go to step 12 .
  6. Remove A/C clutch relay. Using a test light connected to ground, probe terminals D1 and C1 (Pink wire) in A/C clutch relay connector. If test light comes on at both terminals, go to next step. If test light does not come on at both terminals, go to step 14 .
  7. Using a fused jumper wire, jumper terminal C1 (Pink wire) and D3 (Dark Green wire) in A/C clutch relay connector. Observe A/C compressor clutch. If A/C compressor clutch is engaged, go to step 15 . If A/C compressor clutch is not engaged, go to next step.
  8. Disconnect A/C compressor clutch harness connector. Using a DVOM, measure resistance between terminal D3 (Dark Green wire) in A/C clutch relay connector and terminal "A" (Dark Green wire) of A/C compressor clutch harness connector. If resistance is less than 5 ohms, go to next step. If resistance is not as specified, go to step 16 .
  9. Measure resistance between A/C compressor clutch connector terminal "B" (Black wire) and ground. If resistance is less than 5 ohms, PCM circuits are okay. Diagnose A/C-heater system. See AUTOMATIC A/C-HEATER SYSTEMS - AURORA & RIVIERA article. If resistance is not as specified, go to step 25 .
  10. Turn ignition switch to OFF position. Connect scan tool. Turn ignition switch to ON position. Observe A/C clutch relay control circuit status on scan tool. If scan tool displays ON, go to next step. If scan tool does not display ON, go to step 17 .
  11. Disconnect PCM harness connector C1. Check for poor terminal contact at PCM connector C1, terminal No. 27 (Dark Green/White wire). If terminal contacts are faulty, go to step 18 . If no problem is found, go to step 24 .
  12. Remove A/C clutch relay. Using a DVOM, measure voltage between A/C clutch relay terminal C3 (Dark Green/White wire) and ground. If reading is greater than .3 volt, go to step 17 . If reading is not as specified, go to next step.
  13. Disconnect PCM harness connector C1. Using a DVOM, measure resistance between terminal C3 and A/C clutch relay connector and PCM connector C1, terminal No. 27 (Dark Green/White wire). If resistance is less than 5 ohms, go to next step. If resistance is not as specified, go to step 19 .
  14. Using a test light connected to ground, probe terminals D1 and C1 (Pink wires) at A/C clutch relay connector. If test light comes on at either terminal, go to step 20 . If test light does not come on at all, go to step 21 .
  15. Check terminal contact at A/C clutch relay connector. If a terminal contact problem is found, go to step 18 . If no problem is found, go to step 22 .
  16. Check terminal contact at A/C compressor clutch harness connector. If a terminal contact problem is found, go to step 18 . If no problem is found, go to step 23 .
  17. Repair short to voltage in A/C clutch relay control circuit (Dark Green/White wire). Test repair and perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  18. Repair terminal contact. Test repair and perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  19. Repair open in A/C clutch relay control circuit (Dark Green/White wire). Test repair and perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  20. Repair Pink wire between splice and terminal where test light did not come on.
  21. Check for an open in Pink wire between fuse and splice, short in Dark Green wire (blown fuse), shorted relay (blown fuse), or short in Pink wire (blown fuse). Test repair and perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  22. Replace A/C clutch relay. Test repair and perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  23. Repair open in A/C compressor clutch battery feed circuit (Dark Green wire). Test repair and perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  24. Replace PCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Test repair and perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  25. Repair open in compressor clutch ground circuit (Black wire). Test repair and perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

If DTC P1537 is set as a history code, more than likely one of the A/C pressure switches is open. Check A/C system pressures and charge if necessary. If any DTCs are set, repair DTC first, then perform diagnostics. The PCM will energize the A/C clutch when the engine is operating below 4700 RPM.

4.6L: DEVILLE & ELDORADO

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.

When A/C Programmer (ACM) requests A/C operation from PCM, the PCM will ground A/C clutch relay coil. When A/C clutch relay coil is grounded, A/C compressor clutch is energized. The PCM will disable or inhibit compressor operation during high power steering load, if engine is not running, if engine is running at wide open throttle, if ambient temperature is less than 40°F (4°C), or when certain PCM DTCs are set. The A/C compressor clutch is also disengaged during engine cranking in colder weather to prevent A/C slugging.

  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Connect scan tool. Start engine and let idle. Turn A/C on, and select MAX cold and AUTO. Observe scan tool for A/C clutch relay status. If scan tool indicates A/C clutch relay is requested ON, go to next step. If scan tool indicates A/C relay is requested OFF, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) .
  3. Observe A/C compressor clutch. If A/C compressor clutch is engaged, go to next step. If A/C compressor clutch is not engaged, go to step 5 .
  4. Turn A/C controls off. With scan tool status for A/C clutch relay indicating OFF, observe A/C compressor clutch. If A/C compressor clutch is engaged, go to step 9 . If A/C compressor clutch is not engaged, PCM control is okay at this time. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) .
  5. Remove A/C clutch relay from engine compartment fuse block, located in front of left front strut tower. Start engine and let idle. Turn A/C on. Using a test light connected to battery voltage, probe terminal D1 (Dark Green/White wire) in A/C clutch relay connector. If test light does not come on, go to next step. If test light comes on, PCM control is okay. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) .
  6. Using a test light connected to ground, probe terminal D1 (Dark Green/White wire) at A/C clutch relay connector. If test light comes on, go to step 10 . If test light does not come on, go to next step.
  7. Turn ignition switch to OFF position. Disconnect PCM harness connector C1. Using a DVOM, measure resistance of Dark Green/White wire between PCM harness connector C1, terminal No. 25 and A/C clutch relay connector terminal D1. If resistance is 5 ohms or less, go to step 11 . If resistance is greater than 5 ohms, go to next step.
  8. Repair open in A/C clutch relay control circuit (Dark Green/White wire). Test repair and perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  9. Check for the following and repair as necessary: Short to ground in A/C clutch relay control circuit (Dark Green/White wire). Stuck closed switch contacts in A/C clutch relay. Short to voltage in A/C compressor clutch battery feed circuit (Dark Green wire). Test repair and perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no problem is found, go to step 11 .
  10. Repair A/C clutch relay control circuit (Dark Green/White wire) for a short to voltage. Test repair and perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  11. Check for poor terminal contact at PCM harness connector C1, terminal No. 25 and A/C clutch relay connector terminal D1 (Dark Green/White wire). Repair as necessary. Test repair and perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If connections are okay, go to next step.
  12. Replace PCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Test repair and perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  1. Diagnostic Step 2) - The PCM is not allowing A/C compressor clutch operation (DTC set or low ambient temperature), or PCM may not have received a request for A/C operation. PCM control of compressor clutch can be verified by turning ignition switch to OFF position. Using scan tool, command A/C compressor clutch on and off. Listen for A/C compressor clutch to engage and disengage. If PCM control is verified, A/C compressor clutch engages and disengages, perform A/C-heater system self-diagnostics. See AUTOMATIC A/C-HEATER SYSTEMS -AURORA & RIVIERA article. If PCM control is not verified, perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  2. Diagnostic Step 4) - Check for an intermittent condition and/or improper A/C system pressures. Check for A/C-heater system DTCs by performing A/C-heater system self-diagnostics. See AUTOMATIC A/C-HEATER SYSTEMS - AURORA & RIVIERA article.
  3. Diagnostic Step 5) - No A/C compressor clutch operation may be caused by a blown fuse, faulty A/C clutch relay, improper A/C system pressures (open A/C pressure switches), faulty A/C compressor clutch coil or open A/C compressor clutch coil ground circuit. For additional diagnosis, see AUTOMATIC A/C-HEATER SYSTEMS - AURORA & RIVIERA article.

4.6L: SEVILLE

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.

When A/C Programmer (ACM) requests A/C operation from PCM, the PCM will ground A/C clutch relay coil. When A/C clutch relay coil is grounded, compressor clutch is energized. PCM will disable or inhibit compressor operation during high power steering load, if engine is not running, if engine is running at wide open throttle, if ambient temperature is less than 40°F (4°C) or when certain PCM DTCs are set. The compressor clutch is also disengaged during engine cranking in colder weather to prevent A/C slugging.

  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Connect scan tool. Start engine and let idle. Turn A/C on, and select MAX cold and AUTO. Observe scan tool for A/C clutch relay status. If scan tool indicates A/C clutch relay is requested ON, go to next step. If scan tool indicates A/C relay is requested OFF, see «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) .
  3. Observe A/C compressor clutch. If A/C compressor clutch is engaged, go to next step. If A/C compressor clutch is not engaged, go to step 5 .
  4. Turn A/C controls off. With scan tool status for A/C clutch relay indicating OFF, observe A/C compressor clutch. If A/C compressor clutch is engaged, go to step 9 . If A/C compressor clutch is not engaged, PCM control is okay at this time. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) .
  5. Remove A/C clutch relay from underhood junction block. Ensure engine is running at idle with A/C on. Using a test light connected to battery voltage, probe terminal A11 (Dark Green/White wire) at A/C clutch relay connector. See «WIRING DIAGRAMS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__wiring-diagrams) . If test light does not come on, go to next step. If test light comes on, PCM control is okay. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) .
  6. Using a test light connected to ground, probe terminal A11 (Dark Green/White wire) at A/C clutch relay connector. If test light comes on, go to step 10 . If test light does not come on, go to next step.
  7. Turn ignition switch to OFF position. Disconnect PCM harness connector C1. Using a DVOM, measure resistance of Dark Green/White wire between PCM harness connector C1, terminal No. 27 and A/C clutch relay connector terminal A11. If resistance is 5 ohms or less, go to step 11 . If resistance is greater than 5 ohms, go to next step.
  8. Repair open in A/C clutch relay control circuit (Dark Green/White wire). Verify A/C system operation.
  9. Check for the following and repair as necessary: Short to ground in A/C clutch relay control circuit (Dark Green/White wire). Stuck closed switch contacts in A/C clutch relay. Short to voltage in compressor clutch battery feed circuit (Dark Green wire). Verify A/C system operation after repair is completed. If no problem is found, go to step 11 .
  10. Repair A/C clutch relay control circuit (Dark Green/White wire) for a short to voltage. Verify A/C system operation.
  11. Check for poor terminal contact at PCM harness connector C1, terminal No. 27 and A/C clutch relay connector terminal A11 (Dark Green/White wire). Repair as necessary. If connections are okay, go to next step.
  12. Replace PCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Test repair and perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  1. Diagnostic Step 2) - The PCM is not allowing A/C compressor clutch operation (DTC set or low ambient temperature), or PCM may not have received a request for A/C operation. PCM control of A/C compressor clutch can be verified by turning ignition switch to OFF position. Using scan tool, command A/C compressor clutch on and off. Listen for A/C compressor clutch to engage and disengage. If PCM control is verified, A/C compressor clutch engages and disengages, perform A/C-heater system self-diagnostics. See AUTOMATIC A/C-HEATER SYSTEMS - SEVILLE article. If PCM control is not verified, perform OBD System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
  2. Diagnostic Step 4) - Check for an intermittent condition and/or improper A/C system pressures. Check for A/C-heater system DTCs by performing A/C-heater system self-diagnostics. Perform A/C-heater system self-diagnostics. See AUTOMATIC A/C-HEATER SYSTEMS - SEVILLE article.
  3. Diagnostic Step 5) - If the test light comes on, this means the PCM can command the A/C relay on. No A/C compressor clutch operation may be caused by a blown fuse, faulty A/C clutch relay, improper A/C system pressures (open A/C pressure switches), faulty A/C compressor clutch coil, or open A/C compressor clutch coil ground circuit. For additional diagnosis, see AUTOMATIC A/C-HEATER SYSTEMS - SEVILLE article.

5.7L: CAMARO, CORVETTE & FIREBIRD

Note. The following diagnostic procedures apply to manual A/C-heater systems only. For diagnosis of automatic A/C-heater systems, see appropriate AUTOMATIC A/C-HEATER SYSTEMS - CORVETTE article.

The A/C clutch relay is PCM controlled to delay A/C compressor clutch engagement after A/C is turned on. This allows PCM to adjust engine RPM before the A/C compressor clutch engages. The PCM will engage compressor clutch any time A/C has been requested, unless one or more of the following conditions occur

  1. Coolant temperature is high.
  2. A/C system pressure is low.
  3. A/C system pressure is high.
  4. During wide open throttle.
  5. High engine RPM.
  6. Certain DTCs are set.

When A/C-heater control panel is placed in A/C mode, a 12-volt signal is sent to PCM. When PCM receives this signal, PCM will ground A/C clutch relay control circuit to energize A/C clutch relay. This is shown on scan tool as A/C REQUEST YES.

When an A/C request has been detected by PCM, the PCM will ground A/C clutch relay control circuit. As a result, relay contacts close, allowing current to flow through relay to compressor clutch. When A/C REQUEST has been detected by PCM, cooling fans will turn on when A/C system pressure is greater than a predetermined value.

Note. The following test applies only to A/C request circuit. If A/C request circuit is okay and no DTCs are set, but A/C compressor clutch will not engage, further diagnosis is necessary. See appropriate MANUAL A/C-HEATER SYSTEMS article.

  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Check if any DTCs are set. If any DTCs are set, perform diagnosis for DTCs first. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no DTCs are set, go to next step.
  3. Install scan tool. Start engine and let idle. Ensure A/C is off. Using scan tool, view ENG 1 - A/C REQUEST on display. If scan tool displays YES, go to step 8 . If scan tool does not display YES, go to next step.
  4. Turn A/C on. If scan tool displays A/C REQUEST - YES, system is okay at this time. If scan tool does not display A/C REQUEST - YES, go to next step.
  5. Turn ignition switch to OFF position. Disconnect PCM harness connector C1. Turn ignition on, engine off. Using a DVOM, measure voltage between ground and PCM harness connector C1, terminal No. 47 (Dark Green/White wire). Turn A/C on. If reading is near battery voltage, go to step 10 . If reading is not as specified, go to next step.
  6. Turn ignition switch to OFF position. Disconnect HVAC programmer harness connector. Using a DVOM, check for continuity in Dark Green/White wire between HVAC programmer harness connector and PCM harness connector C1, terminal No. 47. If continuity is present, go to next step. If continuity is not present, go to step 11 .
  7. Using a test light connected to battery voltage, probe A/C request circuit (Dark Green/White wire) at PCM harness connector C1, terminal No. 47. If test light comes on, go to step 12 . If test light does not come on, go to step 9 .
  8. Check A/C request circuit (Dark Green/White wire) for a short to voltage. Repair as necessary. If no problem is found, go to next step.
  9. Diagnose HVAC system further. See appropriate MANUAL A/C-HEATER SYSTEMS article. If further diagnosis cannot solve problem, replace HVAC programmer. Verify system operation.
  10. Check for poor PCM harness connections. Repair as necessary. If no problem is found, go to step 13 .
  11. Repair open in A/C request circuit (Dark Green/White wire) between HVAC programmer and PCM. Verify system operation.
  12. Repair short to ground in A/C request circuit (Dark Green/White wire) between HVAC programmer and PCM. Verify system operation.
  13. Replace PCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Test repair and perform OBD System Check in appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

A/C CLUTCH CIRCUIT DIAGNOSIS (LIGHT TRUCKS & VANS)

To save diagnostic time, ALWAYS check for blown fuses or fusible links before proceeding with diagnosis. If fuses are blown, locate and repair short circuit before replacing fuses. Ensure all related relay and wire harness connections are clean and tight. Repair as necessary. See WIRING DIAGRAMS .

Note. Vehicles may be equipped with a PCM using an Electronically Erasable Programmable Read Only Memory (EEPROM). When replacing PCM, the new PCM must be programmed.

The PCM receives an A/C request signal from A/C selector switch over serial data line. When A/C is requested, PCM provides a ground path to A/C clutch relay control circuit. When relay circuit is grounded, A/C clutch relay is energized. After A/C request has been selected, PCM will delay grounding A/C clutch relay control circuit for .3 seconds. This allows PCM to adjust engine idle RPM for additional load. The A/C clutch relay is energized unless one or more of the following conditions occur

  1. Hot engine restart.
  2. Engine speed is greater than 6000 RPM.
  3. During wide open throttle.
  4. During Idle Air Control (IAC) valve reset.

The A/C clutch relay will remain de-energized when DTC P0530 is set, or if there is no A/C request signal due to an open A/C select switch circuit. For additional diagnosis, see appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article.

Note. If DTC P0530 is set, do not perform this diagnostic procedure. Diagnose appropriate DTC before proceeding. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Install scan tool. Check if DTC P0530 is set. If DTC P0530 is set, see appropriate SELF-DIAGNOSTIC article in ENGINE PERFORMANCE. If DTC P0530 is not set, go to next step.
  3. Turn ignition on, engine off. Check if A/C compressor clutch is engaged. If A/C compressor clutch is engaged, go to next step. If A/C compressor clutch is not engaged, go to step 5 .
  4. Disconnect A/C clutch relay. If A/C compressor clutch disengages, go to step 6 . If A/C compressor clutch does not disengage, go to step 7 .
  5. Start engine and allow it to reach normal operating temperature. Cycle A/C selector switch on and off. If A/C compressor clutch cycles on and off, go to step 8 . If A/C compressor clutch does not cycle on and off, go to step 9 .
  6. Using a test light connected to battery voltage, probe A/C clutch relay control circuit terminal (Dark Green/White wire) at A/C clutch relay connector. If test light comes on, go to step 10 . If test light does not come on, go to step 11 .
  7. Disconnect A/C compressor clutch harness connector. If A/C compressor clutch disengages, go to step 12 . If A/C compressor clutch does not disengage, go to step 13 .
  8. Turn ignition on, engine off. Install A/C manifold gauge set. Observe A/C high-side pressure readings on gauge set and compare to scan tool reading. If high-side pressure readings are within 20 psi (1.4 kg/cm 2 ) of each other, go to step 36 . If pressures are not as specified, go to step 14 .
  9. Turn A/C on, then off. If scan tool indicates A/C was requested, then not requested, go to step 15 . If operation is not as specified, go to step 16 .
  10. Check A/C clutch relay control circuit (Dark Green/White wire) for a short to ground. Repair as necessary. Go to step 36 . If no problem is found, go to step 22 .
  11. Replace A/C clutch relay. Go to step 36 .
  12. Repair short to voltage in A/C compressor clutch battery feed circuit (Dark Green wire). Go to step 36 .
  13. Replace faulty A/C compressor clutch coil. Go to step 36 .
  14. Turn ignition on, engine off. Disconnect A/C pressure sensor harness connector. Using a DVOM, measure voltage between battery voltage and Black wire at A/C pressure sensor harness connector. If reading is battery voltage, go to step 18 . If reading is not as specified, go to step 19 .
  15. With ignition on, engine off, observe A/C HIGH-SIDE pressure reading on scan tool. If reading is 40-430 psi (2.8-30.2 kg/cm 2 ), go to step 20 . If reading is not as specified, go to step 21 .
  16. Turn ignition switch to OFF position. Disconnect PCM harness connectors. Turn ignition switch to ON position. Using a test light connected to ground, probe A/C selector switch input circuit (Light Blue wire) at PCM harness connector. Cycle A/C selector switch on and off. If test light toggles on and off, go to next step. If test light does not toggle on and off, go to step 23 .
  17. Check Light Blue wire for a poor connection at PCM. Repair as necessary. Go to step 36 . If no problem is found, go to step 22 .
  18. Replace A/C pressure sensor. Go to step 36 .
  19. Repair open or poor connection in A/C pressure sensor ground circuit (Black wire). Go to step 36 .
  20. Disconnect A/C clutch relay. Using a test light connected to ground, probe A/C clutch relay battery and ignition feed circuits at A/C clutch relay connector. If test light comes on at both circuits, go to step 24 . If test light does not come on at both circuits, go to step 25 .
  21. Connect A/C manifold gauge set. With ignition on, engine off, observe A/C high-side pressure readings on gauge set and scan tool. If high-side pressures are within 20 psi (1.4 kg/cm 2 ) of each other, diagnose A/C-heater system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEM article. If high-side pressures are not as specified, go to step 18 .
  22. Replace PCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Go to step 36 .
  23. Repair A/C request signal circuit (Light Blue wire) from A/C selector switch. Go to step 36 .
  24. Connect a fused jumper wire between A/C clutch relay connector terminals No. 30 and 87. If A/C compressor clutch engages, go to step 26 . If A/C compressor clutch does not engage, leave jumper wire installed and go to step 27 .
  25. If test light does not come on at battery feed terminal, check for a short to ground in A/C compressor clutch battery feed circuit (Dark Green wire), or a faulty A/C compressor clutch diode. Repair as necessary. Go to step 36 . If no problem is found, go to step 28 .
  26. Remove jumper wire. Start engine and let idle. Using a test light connected to battery voltage, probe A/C clutch relay connector terminal No. 86 (Dark Green/White wire). Using scan tool, command A/C clutch relay on. If test light comes on, go to step 11 . If test light does not come on, go to step 29 .
  27. Disconnect A/C compressor clutch harness connector. Using a test light connected to ground, probe Dark Green wire at A/C compressor clutch harness connector. If test light comes on, go to step 30 . If test light does not come on, go to step 31 .
  28. Repair open in battery or ignition feed circuits to A/C clutch relay. Go to step 36 .
  29. Using a test light connected to ground, probe A/C clutch relay connector terminal No. 86 (Dark Green/White wire). If test light comes on, go to step 32 . If test light does not come on, go to step 33 .
  30. Using a test light connected to battery voltage, probe A/C compressor clutch ground circuit (Black wire) at A/C compressor clutch harness connector. If test light comes on, go to step 34 . If test light does not come on, go to step 35 .
  31. Repair open in A/C compressor clutch battery feed circuit (Dark Green wire). Go to step 36 .
  32. Check A/C clutch relay control circuit (Dark Green/White wire) for a short to voltage. Repair as necessary. Go to step 36 . If no problem is found, go to step 17 .
  33. Check A/C clutch relay control circuit (Dark Green/White wire) for an open or poor connection. Repair as necessary. Go to step 36 . If no problem is found, go to step 17 .
  34. Replace A/C compressor clutch coil. Go to step 36 .
  35. Repair open or poor connection in A/C compressor clutch ground circuit (Black wire). Go to next step.
  36. Start engine and let idle. Cycle A/C selector switch on and off. If A/C compressor clutch cycles on and off, system is okay at this time. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) . If operation is not as specified, go to step 2 .

An A/C refrigerant pressure less than 43 psi (3.0 kg/cm 2 ), or greater than 428 psi (30.1 kg/cm 2 ) will cause PCM to disable A/C compressor clutch. With engine running and A/C on, use scan tool to monitor A/C high-side system pressure for 2 minutes. If pressure goes out of range, diagnose A/C-heater system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article.

When A/C mode is selected, a 12-volt signal is supplied to A/C request input terminal at PCM. A/C clutch relay is controlled through PCM. The PCM monitors A/C refrigerant pressure. If A/C refrigerant pressure and engine operating conditions are within a specific calibrated acceptable range, PCM will enable A/C clutch relay. This is done by providing a ground path for A/C clutch relay coil within PCM. When A/C clutch relay is enabled, battery voltage is supplied to compressor clutch coil.

The PCM will enable A/C compressor clutch whenever engine is running and A/C has been requested, unless

  1. Throttle angle is greater than 90 percent.
  2. A/C head pressure is greater than 414 psi (29.1 kg/cm 2 ).
  3. A/C head pressure is less than 35 psi (2.5 kg/cm 2 ).
  4. Ignition voltage is less than 10.5 volts.
  5. Engine speed is greater than 4500 RPM for 5 seconds.
  6. Engine coolant temperature is greater than 257°F (125°C).
  7. Intake air temperature is less than 41°F (5°C).
  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. Check for any DTCs that may be set. If any DTCs are set, perform diagnosis for that DTC first. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no DTCs are set, go to next step.
  3. Ensure ambient temperature is greater than 48°F (9°C). Ensure engine coolant temperature is less than 246°F (119°C). Turn A/C off. Start engine and let idle. Observe A/C compressor clutch. If A/C compressor clutch is engaged, go to step 21 . If A/C compressor clutch is not engaged, go to next step.
  4. Run engine at 1000-1500 RPM. Select A/C mode on A/C control panel. Observe A/C compressor clutch. If A/C compressor clutch is engaged, system is okay at this time. Problem may be intermittent. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) . If A/C compressor clutch is not engaged, go to next step.
  5. With A/C mode still selected, observe A/C REQUEST display on scan tool. If A/C REQUEST displays YES, go to step 9 . If A/C REQUEST does not display YES, go to next step.
  6. Turn ignition switch to OFF position. Disconnect PCM harness connectors. Turn ignition switch to ON position. With A/C still selected, use a DVOM and measure voltage on A/C request circuit (Dark Green/White wire) at PCM harness connector. See «WIRING DIAGRAMS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__wiring-diagrams) . If reading is near battery voltage, go to step 8 . If reading is not as specified, go to next step.
  7. Check A/C request circuit (Dark Green/White wire) for an open, short to ground or poor connection at A/C control panel. Repair as necessary. Go to step 37 . If no problem is found, diagnose A/C-heater controls. See MANUAL A/C-HEATER SYSTEMS - MONTANA, SILHOUETTE & VENTURE article.
  8. Check A/C request circuit (Dark Green/White wire) for a poor connection at PCM. Repair as necessary. Go to step 37 . If no problem is found, go to step 35 .
  9. Observe A/C pressure sensor display on scan tool. If reading is .35-4.27 volts, go to step 12 . If reading is not as specified, go to next step.
  10. Install A/C manifold gauge set. Observe high-side refrigerant pressure on gauge. If high-side refrigerant pressure is 34-414 psi (2.3-28.5 kg/cm 2 ), go to next step. If high-side refrigerant pressure is not as specified, charge A/C system. Go to step 37 .
  11. Turn ignition switch to OFF position. Disconnect PCM and A/C pressure sensor harness connectors. Using a DVOM, measure resistance of the following circuits between PCM and A/C pressure sensor harness connectors: A/C pressure sensor signal circuit (Red/Black wire). 5-volt reference "B" circuit (Gray wire). Sensor ground circuit (Orange/Black wire). If any resistance measurement is greater than 5 ohms, locate and repair cause of high resistance in circuit as necessary, then go to step 37 . If no resistance measurement is greater than 5 ohms, go to step 18 .
  12. Disconnect A/C clutch relay. Using a test light connected to ground, probe ignition feed circuits at A/C clutch relay connector. If test light comes on, go to next step. If test light does not come on, go to step 31 .
  13. Connect a fused jumper wire between A/C clutch relay ignition feed circuit and A/C compressor clutch battery feed circuit (Dark Green wire) at A/C clutch relay connector. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, leave jumper wire in place and go to step 15 .
  14. Check for poor connections at A/C clutch relay. Repair as necessary. Go to step 37 . If no problem is found, go to step 32 .
  15. Disconnect A/C compressor clutch harness connector. Connect a test light between A/C compressor clutch battery feed circuit (Dark Green wire) and A/C compressor clutch ground circuit (Black wire). If test light comes on, go to next step. If test light does not come on, go to step 17 .
  16. Check for poor connections at A/C compressor clutch harness connector. Repair as necessary. Go to step 37 . If no problem is found, go to step 33 .
  17. Check for an open or short to ground in A/C compressor clutch battery feed circuit (Dark Green wire). Repair as necessary. Go to step 37 . If no problem is found, go to step 34 .
  18. Leave PCM and A/C pressure sensor harness connectors disconnected at PCM. Turn ignition switch to ON position. Using a DVOM, measure voltage between ground and A/C pressure sensor signal circuit (Red/Black wire). If reading is near zero volts, go to next step. If reading is not as specified, go to step 20 .
  19. Check for the following conditions: 5-volt reference "B" circuit (Gray wire) for a poor connection at PCM or A/C pressure sensor. A/C pressure sensor signal circuit (Red/Black wire) for a poor connection at PCM or A/C pressure sensor. Sensor ground circuit (Black wire) for a poor connection at A/C pressure sensor. Repair as necessary and go to step 37 . If no problem is found, go to step 36 .
  20. Locate and repair short to voltage in A/C pressure sensor signal circuit (Red/Black wire). Go to step 37 .
  21. Turn ignition on, A/C off. Observe A/C REQUEST on scan tool. If A/C REQUEST displays YES, go to next step. If A/C REQUEST does not display YES, go to step 24 .
  22. Turn ignition switch to OFF position. Disconnect PCM harness connectors. Turn ignition on, A/C off. Using a DVOM, measure voltage between ground and A/C request signal circuit (Dark Green/White wire) at PCM harness connector. If reading is near battery voltage, go to next step. If reading is not as specified, go to step 35 .
  23. Turn ignition switch to OFF position. Disconnect A/C control head/programmer harness connectors. Turn ignition switch to ON position. Check A/C request circuit for a short to voltage. Repair as necessary. Go to step 37 . If no problem is found, diagnose A/C controls. See MANUAL A/C-HEATER SYSTEMS - MONTANA, SILHOUETTE & VENTURE article.
  24. Disconnect A/C clutch relay. Start engine and observe A/C compressor clutch. If A/C compressor clutch is engaged, go to step 29 . If A/C compressor clutch is not engaged, go to next step.
  25. Using a test light connected to ground, probe A/C compressor clutch battery feed circuit (Dark Green wire) at A/C clutch relay harness connector. If test light comes on, go to step 27 . If test light does not come on, go to next step.
  26. Replace A/C clutch relay. Go to step 37 .
  27. Turn ignition switch to OFF position. Disconnect PCM harness connectors. Using a test light connected to battery voltage, probe A/C clutch relay control circuit (Dark Green/White wire) at PCM harness connector. If test light comes on, go to next step. If test light does not come on, go to step 28 .
  28. Repair short to ground in A/C clutch relay control circuit (Dark Green/White wire). Go to step 37 .
  29. Turn ignition switch to OFF position. Disconnect A/C compressor clutch harness connector. Start engine and observe A/C compressor clutch. If A/C compressor clutch is engaged, go to step 33 . If A/C compressor clutch is not engaged, go to next step.
  30. Locate and repair short to voltage in A/C compressor clutch battery feed circuit (Dark Green wire). Go to step 37 .
  31. Repair open or short to ground in ignition feed circuit to A/C clutch relay. Go to step 37 .
  32. Replace A/C clutch relay. Go to step 37 .
  33. Repair A/C compressor clutch. Go to step 37 .
  34. Locate and repair open in A/C compressor clutch ground circuit (Black wire). Go to step 37 .
  35. Replace PCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Go to step 37 .
  36. Replace A/C pressure sensor. Go to next step.
  37. Ensure ambient temperature is greater than 48°F (9°C). Ensure engine coolant temperature is less than 246°F (119°C). With A/C off, start engine and let idle. Observe A/C compressor clutch. If A/C compressor clutch is engaged, go to step 21 . If A/C compressor clutch is not engaged, go to next step.
  38. Run engine at 1000-1500 RPM. Select A/C mode on A/C control panel. Observe A/C compressor clutch. If A/C compressor clutch is engaged, system is okay. If A/C compressor clutch is not engaged, go to step 5 .

Check for poor harness connections at PCM and A/C-heater control panel. Inspect for corrosion, backed-out terminal pins, and broken wires inside insulation. Check for damaged wire harness. If harness and connections are okay, disconnect PCM harness connectors. Connect a DVOM between ground and A/C clutch relay control circuit at PCM harness connector. Turn ignition switch to ON position. Observe DVOM while wiggling harness and connectors. A change in voltage indicates location of fault.

An A/C refrigerant pressure less than 35 psi (2.5 kg/cm 2 ), or greater than 414 psi (29.1 kg/cm 2 ) will cause PCM to disable A/C compressor clutch. With engine running and A/C on, use scan tool to monitor A/C high-side system pressure for 2 minutes. If pressure goes out of range, diagnose A/C-heater system. See MANUAL A/C-HEATER SYSTEMS - MONTANA, SILHOUETTE & VENTURE article.

4.3L: "C", "G", "K", "L", "M", "P", "S" & "T" SERIES (INCLUDING SIERRA & SILVERADO), 5.0L: "C", "G" & "K" SERIES OR 5.7L, 6.5L & 7.4L: "C", "G", "K" & "P" SERIES

Note. The 6.5L diesel engines are equipped with a Powertrain Control Module (PCM). Substitute VCM with PCM in the following test when diagnosing vehicles equipped with diesel engines.

The A/C clutch relay is controlled by Vehicle Control Module (VCM) to delay A/C compressor clutch engagement after A/C is turned on. This allows VCM to adjust engine RPM before A/C compressor clutch engages. VCM will engage A/C compressor clutch any time A/C has been requested unless coolant temperature is high, A/C system pressure is low, A/C system pressure is high, wide open throttle, or high engine RPM.

When A/C-heater control panel is placed in A/C mode, a 12-volt signal is sent to VCM. When VCM receives this signal, VCM will ground A/C clutch relay control circuit to energize A/C clutch relay. This is shown on scan tool as A/C REQUEST YES.

When an A/C request has been detected by VCM, VCM will ground A/C clutch relay control circuit. As a result, relay contacts close, allowing current to flow through relay to A/C compressor clutch. When A/C REQUEST has been detected by VCM, cooling fans will turn on when A/C pressure is greater than a predetermined value.

  1. Install A/C manifold gauge set. Ensure A/C system is fully charged. Charge system if necessary and go to next step.
  2. Start engine and allow it to reach normal operating temperature. Turn A/C on. If A/C compressor clutch engages, then disengages within 60 seconds, diagnose A/C-heater system. See «DIAGNOSTIC AIDS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls) . If operation is not as specified, go to next step.
  3. Turn engine off. Install scan tool. With A/C on, monitor A/C REQUEST on scan tool display. If scan tool displays A/C REQUEST as YES, go to next step. If scan tool does not display A/C REQUEST as YES, go to step 14 .
  4. Monitor A/C evaporator switch on scan tool display. If scan tool indicates switch is closed, go to step 8 . If scan tool does not indicate the switch is closed, go to next step.
  5. Turn ignition switch to OFF position. Disconnect A/C evaporator cycling cut-off switch connector. Turn ignition switch on, engine off. Connect a fused jumper wire between connector terminal "A" and ground. See «WIRING DIAGRAMS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__wiring-diagrams) . If scan tool indicates switch is closed, go to next step. If scan tool does not indicate switch is closed, go to step 27 .
  6. With a test light connected to battery voltage, probe A/C evaporator cycling cut-off switch connector terminal "B". If test light comes on, go to next step. If test light does not come on, go to step 30 .
  7. Replace A/C evaporator cycling cut-off switch. Go to step 33 .
  8. Turn ignition switch to OFF position. Disconnect A/C compressor clutch connector. Start engine. Turn A/C to ON position. With a test light connected to ground, probe A/C clutch signal circuit at A/C compressor clutch connector. If test light comes on, go to next step. If test light does not come on, go to step 16 .
  9. With a test light connected to battery voltage, probe A/C compressor clutch ground terminal. If test light comes on, go to go to step 11 . If test light does not come on, go to next step.
  10. Repair A/C clutch ground circuit. After repair, go to step 33 .
  11. Check for poor connection at A/C compressor clutch connector. If connections are faulty, go to next step. If connections are okay, go to step 13 .
  12. Repair terminals or replace A/C compressor clutch connector. After repairs, go to step 33 .
  13. Replace A/C compressor clutch. After repairs, go to step 33 .
  14. Turn ignition switch to OFF position. Disconnect VCM connector C3. Turn ignition on, engine off. Turn A/C to on position. With a test light connected to ground, probe VCM connector C3 terminal No. 25. If test light comes on, go to step 29 . If test light does not come on, go to next step.
  15. Check for open in A/C request signal circuit between HAVC control module and VCM. If circuit is faulty, go to step 30 . If circuit is okay, go to step 28 .
  16. Reconnect A/C compressor clutch connector. Install scan tool and turn ignition on, engine off. Use scan tool to command A/C relay ON. If relay turns on, go to step 22 . If relay does not turn on, go to next step.
  17. Disconnect A/C relay. With a test light connected to ground, probe ignition voltage circuit at A/C relay connector. If test light comes on, go to step 19 . If test light does not come on, go to next step.
  18. Repair open in A/C relay ignition voltage circuit. Check fuse for A/C relay ignition voltage circuit. If fuse is blown, repair short to ground on circuit. A blown fuse or lack of voltage to fuse may cause other problems or DTCs to set. After repairs, go to step 33 .
  19. With a test light connected to battery voltage, probe A/C relay connector control circuit terminal. Using scan tool, command A/C relay ON. If test light comes on, go to step 25 . If test light does not come on, go to next step.
  20. Check for open or short to voltage in circuit between underhood fuse block A/C relay connector cavity and VCM connector C3 terminal No. 1. If circuit is faulty, go to next step. If circuit is okay, go to step 29 .
  21. Repair open in circuit between underhood fuse block A/C relay connector cavity and VCM connector C3 terminal No. 1. After repairs, go to step 33 .
  22. Remove A/C relay. With a test light connected to ground, probe A/C relay battery feed circuit terminal. If test light comes on, go to step 24 . If test light does not come on, go to next step.
  23. Repair open in A/C relay battery feed circuit. Check fuse for A/C relay battery feed circuit. If fuse is blown, repair short to ground on circuit. A blown fuse or lack of voltage to fuse may cause other problems or DTCs to set. After repairs, go to step 33 .
  24. Turn ignition on, engine off. Connect a fused jumper wire between A/C relay battery feed circuit terminal and A/C compressor clutch circuit terminal. If A/C compressor engages, go to next step. If A/C compressor clutch does not engage, go to step 26 .
  25. Repair open or short to ground in A/C compressor clutch circuit. After repairs, go to step 33 .
  26. Repair open or short to ground in A/C compressor clutch control circuit (Dark Green wire). After repairs, go to step 33 .
  27. Check for open in A/C cycling switch circuit. If circuit is faulty, go to step 30 . If circuit is okay, go to step 29 .
  28. Replace HVAC control assembly. After repairs, go to step 33 .
  29. Check for poor VCM connections. If connections are faulty, go to next step. If connections are okay, go to step 31 .
  30. Repair circuit or connection as necessary. After repairs, go to step 33 .
  31. Replace VCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. After repairs, go to next step.
  32. Start engine and allow to idle until operating temperature is reached. Turn A/C to ON position. If A/C compressor engages within 60 seconds, go to next step. If A/C compressor clutch does not engage within 60 seconds, go to step 2 .
  33. Check for DTCs with scan tool. If scan tool indicates more undiagnosed DTCs, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no additional DTCs are indicated, system is operating normally.

Intermittent conditions can be caused by poor connections, rubbed wire through insulation or a broken wire within the insulation. Check circuits thoroughly. For additional information, see appropriate AUTOMATIC or MANUAL A/C-HEATER SYSTEMS article.

4.8L, 5.3L & 6.0L: SIERRA & SILVERADO

Note. The following diagnostic procedure is only for PCM controlled A/C circuits. For VCM controlled A/C circuits, see 4.3L: "C", "G", "K", "L", "M", "P", "S" & "T" SERIES (INCLUDING SIERRA & SILVERADO) diagnosis.

The PCM controls operation of A/C clutch relay. When any A/C mode is selected on Heating, Ventilation and Air Conditioning (HVAC) control module, a 12-volt signal is sent through the A/C high pressure switch and to the PCM. If conditions are met, the PCM will send another 12-volt signal to the A/C compressor cycling switch, which is the ground signal. When these two signals are received by the PCM, the PCM supplies a ground for the A/C relay.

The PCM controlled HVAC system consists of the following components

  1. A/C high pressure switch.
  2. A/C compressor cycling switch.
  3. A/C compressor relay.
  4. PCM

The PCM will engage the A/C compressor clutch unless one or more of the following conditions occur

  1. Throttle angle at 100 percent.
  2. A/C compressor cycling switch pressure is less than 18 psi (1.2 km/cm 2 ) or greater than 49 psi (3.4 km/cm 2 ).
  3. A/C high pressure cut-out switch pressure is greater than 420 psi (29.5 km/cm 2 ).
  4. Engine speed is greater than 5500 RPM.
  5. Engine coolant temperature greater than 250°F (121°C).

Any condition described above will prevent operation of the A/C compressor clutch.

  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If OBD System Check has been performed, go to next step.
  2. This diagnostic procedure only diagnoses the A/C compressor clutch circuit. This procedure assumes the following conditions are true: A/C system is fully charged. A/C compressor has no mechanical failures. Engine coolant temperature is greater than 140°F (60°C), but less than 250°F (121°C). HVAC control module is functioning normally. Start engine and turn HVAC controls to off position. If A/C compressor clutch is engaged, go to step 12 . If A/C compressor clutch is not engaged, go to next step.
  3. Select any A/C position on HVAC control panel. Set blower switch to high. If A/C compressor clutch engages, system is operating properly at this time. If A/C compressor clutch is not engaged, go to next step.
  4. Check condition of both A/C and IGN E fuses (10-amp). If both fuses are okay, go to next step. If one or more fuses are blown, go to step 28 .
  5. Connect scan tool and monitor A/C request signal. If scan tool displays A/C request as YES, go to next step. If scan tool displays A/C request as NO, go to step 20 .
  6. Monitor A/C compressor cycling switch signal with scan tool. If scan tool displays A/C cycling switch as closed, go to next step. If scan tool does not display A/C cycling switch as closed, go to step 24 .
  7. Turn ignition switch to OFF position. Disconnect A/C clutch relay. Turn ignition switch on, engine off. With test light connected to battery voltage, probe A/C clutch relay control circuit (Dark Green/White wire). See «WIRING DIAGRAMS»(/gmc/savana/i-1996-2002/remont/ac-compressor/#hvac-system-compressor-clutch-controls__wiring-diagrams) . Using scan tool, command A/C clutch relay on and off. If test light turns on and off, go to next step. If test light does not turn on and off, go to step 31 .
  8. With a test light connected to ground, probe both A/C relay battery voltage supply circuits. If test light comes on at both terminals, go to next step. If test light does not come on at both terminals, go to step 32 .
  9. Connect a fused jumper between battery voltage circuit and A/C compressor clutch circuit (Dark Green wire). If A/C compressor clutch engages, go to step 34 . If A/C compressor clutch does not engage, go to next step.
  10. With a fused jumper connected, raise and support vehicle. Disconnect A/C compressor clutch connector. With a test light connected to ground, probe A/C compressor clutch connector feed from relay terminal (Dark Green wire). If test light comes on, go to next step. If test light does not come on, go to step 33 .
  11. Connect a test light between terminals of A/C compressor clutch connector. If test light comes on, go to step 35 . If test light does not come on, go to step 36 .
  12. Monitor A/C request signal on scan tool. If scan tool indicates A/C request as YES, go to next step. If scan tool indicates A/C request as NO, go to step 16 .
  13. Disconnect A/C high pressure cut-out switch located on rear of compressor. If scan tool indicates A/C request as YES, go to next step. If scan tool indicates A/C request as NO, diagnose A/C-heater system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article.
  14. Turn ignition switch to OFF position. Disconnect PCM connector C2. Turn ignition switch to ON position. Use a DVOM to measure voltage between PCM connector C2 A/C request terminal (Dark Green/White wire) and ground. If any voltage reading is indicated, go to step 37 . If no voltage reading is indicated, go to next step.
  15. Turn ignition switch to OFF position. Use a DVOM to measure resistance between A/C request terminal (Dark Green/White wire) and all other terminals at connector C2. If reading is 0-2 ohms at any terminal, go to step 38 . If reading is not 0-2 ohms at any terminal, go to step 55 .
  16. Disconnect A/C clutch relay. If A/C compressor clutch disengages, go to next step. If A/C compressor clutch does not disengage, go to step 39 .
  17. With a test light connected to battery voltage, probe A/C clutch relay control circuit (Dark Green/White wire) at relay connector. If test light comes on, go to next step. If test light does not come on, go to step 40 .
  18. Turn ignition switch to OFF position. Disconnect PCM connector C2. With a test light connected to battery voltage, probe A/C clutch relay control circuit terminal (Dark Green/White wire) at PCM connector C2. If test light comes on, go to step 41 . If test light does not come on, go to next step.
  19. Use a DVOM to measure resistance between A/C clutch relay control circuit terminal (Dark Green/White wire) and all other terminals at connector C2. If reading is 0-2 ohms at any terminal, go to step 42 . If reading is not 0-2 ohms at any terminal, go to step 55 .
  20. Turn engine off. Disconnect A/C high pressure cut-out switch located on rear of compressor. Turn ignition switch to ON position. Use a DVOM to measure voltage between ground and A/C request circuit (Dark Green/White wire) on HVAC module side. If battery voltage is indicated, go to next step. If battery voltage is not indicated, diagnose A/C-heater system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article.
  21. Connect a fused jumper wire between A/C high pressure cut-out switch connector terminals. Start engine and monitor A/C request on scan tool. If scan tool indicates A/C request as YES, go to step 43 . If scan tool indicates A/C request as NO, go to next step.
  22. Turn ignition switch to OFF position. Disconnect PCM connector C2. Use a DVOM to check for continuity of A/C request signal circuit between PCM and A/C high pressure cut-out switch (Dark Green/White wire). If continuity is indicated, go to next step. If continuity is not indicated, go to step 45 .
  23. Use a DVOM to check continuity of A/C request signal circuit to ground. If continuity is indicated, go to step 46 . If continuity is not indicated, go to step 54 .
  24. Turn engine off. Disconnect A/C compressor cycling switch connector to the accumulator. Turn ignition switch to ON position. Use DVOM to measure voltage between battery ground and A/C compressor cycling switch signal circuit (Dark Green wire). If battery voltage is indicated, go to next step. If battery voltage is not indicated, go to step 26 .
  25. Connect a fused jumper wire between A/C compressor cycling switch connector terminals. If scan tool indicates A/C compressor cycling switch as closed, go to step 47 . If scan tool does not indicate A/C compressor cycling switch as closed, go to step 49 .
  26. Turn ignition switch to OFF position. Disconnect PCM connector C2. Use a DVOM to check continuity of A/C compressor cycling switch circuit between PCM and cycling switch (Dark Green wire). If continuity is indicated, go to next step. If continuity is not indicated, go to step 50 .
  27. Use a DVOM to check continuity between A/C compressor cycling switch circuit and ground. If continuity is indicated, go to step 51 . If continuity is not indicated, go to step 54 .
  28. If A/C fuse (10-amp) is blown, go to step 52 . If A/C fuse is okay, go to next step.
  29. Remove A/C clutch relay from underhood electrical center. With a test light connected to battery voltage, probe A/C clutch relay ignition supply circuit on fuse side. If test light come on, go to step 52 . If test light does not come on, go to next step.
  30. Raise and support vehicle. Disconnect A/C compressor clutch connector. With a test light connected to battery voltage, probe A/C compressor clutch supply circuit terminal (Dark Green wire). If test light comes on, go to step 53 . If test light does not come on, replace A/C compressor clutch.
  31. Turn ignition switch to OFF position. Disconnect PCM connector C2. Use a DVOM to check continuity of A/C relay control circuit between PCM and underhood electrical center (Dark Green/White wire). If continuity is indicated, go to step 54 . If continuity is not indicated, go to step 56 .
  32. Repair open in circuit that did not turn test light on. Recheck system operation.
  33. Repair open in A/C clutch circuit between relay and clutch. Recheck system operation.
  34. Replace A/C clutch relay. Recheck system operation.
  35. Check for proper terminal contact at A/C compressor clutch. If poor connection is found, repair as necessary and recheck system operation. If connections are okay, replace A/C compressor clutch.
  36. Repair open in A/C clutch ground circuit (Black wire). Recheck system operation.
  37. Repair short to voltage in A/C request circuit (Dark Green/White wire) between A/C high pressure cut-out switch and PCM. Recheck system operation.
  38. Repair short to voltage in circuit that had continuity. Recheck system operation.
  39. Repair short to voltage in Dark Green wire between A/C clutch relay and A/C compressor clutch. Recheck system operation.
  40. Replace A/C clutch relay. Recheck system operation.
  41. Repair short to ground in Dark Green/White wire between A/C clutch relay and PCM. Recheck system operation.
  42. Repair short to ground in circuit that had continuity. Recheck system operation.
  43. Check for proper terminal contact at A/C high pressure cut-out switch. Repair as necessary and recheck system operation. If connections are okay, go to next step.
  44. Replace A/C high pressure cut-out switch. Recheck system operation.
  45. Repair open in Dark Green/White wire between A/C high pressure cut-out switch and PCM. Recheck system operation.
  46. Repair short to ground in Dark Green/White wire between A/C high pressure cut-out switch and PCM. Recheck system operation.
  47. Check for proper terminal contact at A/C compressor cycling switch. Repair as necessary and recheck system operation. If connections are okay, go to next step.
  48. Replace A/C compressor cycling switch. Recheck system operation.
  49. Repair open in A/C compressor cycling switch ground circuit (Black wire). Recheck system operation.
  50. Repair open in A/C compressor cycling switch signal circuit (Dark Green wire). Recheck system operation.
  51. Repair short to ground in A/C compressor cycling switch signal circuit (Dark Green wire). Recheck system operation.
  52. Replace underhood electrical center. Recheck system operation.
  53. Check for, and repair, short to ground in Dark Green wire. If wire is okay, replace shorted A/C compressor clutch diode. Recheck system operation.
  54. Check for proper terminal contact at PCM. Repair as necessary and recheck system operation. If connections are okay, go to next step.
  55. Replace PCM and program. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION in ENGINE PERFORMANCE. Recheck system operation.
  56. Repair open in A/C clutch relay control circuit (Dark Green/White wire) between underhood fuse block and PCM. Recheck system operation.

WIRING DIAGRAMS

Note. Wiring diagrams for Aurora, Park Avenue, and Riviera are not available from manufacturer.

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

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

A/C Compressor Clutch Control Circuit Wiring Diagram (Astro & Safari). Scheme 2

Scheme 2: A/C Compressor Clutch Control Circuit Wiring Diagram (Astro & Safari)
Scheme 2: A/C Compressor Clutch Control Circuit Wiring Diagram (Astro & Safari)

A/C Compressor Clutch Control Circuit Wiring Diagram (Blazer, Jimmy, Sonoma & S10 Pickup - With Manual A/C-Heater System & 4.3L VINs W & X Engine). Scheme 3

Scheme 3: A/C Compressor Clutch Control Circuit Wiring Diagram (Blazer, Jimmy, Sonoma & S10 Pickup - With Manual A/C-Heater System & 4.3L VINs W & X Engine)
Scheme 3: A/C Compressor Clutch Control Circuit Wiring Diagram (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 (Blazer, Bravada, Envoy & Jimmy - With Automatic A/C-Heater System). Scheme 4

Scheme 4: A/C Compressor Clutch Control Circuit Wiring Diagram (Blazer, Bravada, Envoy & Jimmy - With Automatic A/C-Heater System)
Scheme 4: A/C Compressor Clutch Control Circuit Wiring Diagram (Blazer, Bravada, Envoy & Jimmy - With Automatic A/C-Heater System)

A/C Compressor Clutch Control Circuit Wiring Diagram (Bonneville, Eighty Eight, LeSabre & LSS). Scheme 5

Scheme 5: A/C Compressor Clutch Control Circuit Wiring Diagram (Bonneville, Eighty Eight, LeSabre & LSS)
Scheme 5: A/C Compressor Clutch Control Circuit Wiring Diagram (Bonneville, Eighty Eight, LeSabre & LSS)

A/C Compressor Clutch Control Circuit Wiring Diagram (Camaro & Firebird - With 3.8L VIN K Engine). Scheme 6

Scheme 6: A/C Compressor Clutch Control Circuit Wiring Diagram (Camaro & Firebird - With 3.8L VIN K Engine)
Scheme 6: A/C Compressor Clutch Control Circuit Wiring Diagram (Camaro & Firebird - With 3.8L VIN K Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram (Camaro & Firebird - With 5.7L VIN G Engine). Scheme 7

Scheme 7: A/C Compressor Clutch Control Circuit Wiring Diagram (Camaro & Firebird - With 5.7L VIN G Engine)
Scheme 7: A/C Compressor Clutch Control Circuit Wiring Diagram (Camaro & Firebird - With 5.7L VIN G Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram (Catera). Scheme 8

Scheme 8: A/C Compressor Clutch Control Circuit Wiring Diagram (Catera)
Scheme 8: A/C Compressor Clutch Control Circuit Wiring Diagram (Catera)

A/C Compressor Clutch Control Circuit Wiring Diagram (Cavalier & Sunfire). Scheme 9

Scheme 9: A/C Compressor Clutch Control Circuit Wiring Diagram (Cavalier & Sunfire)
Scheme 9: A/C Compressor Clutch Control Circuit Wiring Diagram (Cavalier & Sunfire)

A/C Compressor Clutch Control Circuit Wiring Diagram (Century & Regal). Scheme 10

Scheme 10: A/C Compressor Clutch Control Circuit Wiring Diagram (Century & Regal)
Scheme 10: A/C Compressor Clutch Control Circuit Wiring Diagram (Century & Regal)

A/C Compressor Clutch Control Circuit Wiring Diagram (Corvette). Scheme 11

Scheme 11: A/C Compressor Clutch Control Circuit Wiring Diagram (Corvette)
Scheme 11: A/C Compressor Clutch Control Circuit Wiring Diagram (Corvette)

A/C Compressor Clutch Control Circuit Wiring Diagram (Cutlass & Malibu). Scheme 12

Scheme 12: A/C Compressor Clutch Control Circuit Wiring Diagram (Cutlass & Malibu)
Scheme 12: A/C Compressor Clutch Control Circuit Wiring Diagram (Cutlass & Malibu)

A/C Compressor Clutch Control Circuit Wiring Diagram ("C" & "K" Pickups, Escalade, Suburban, Tahoe & Yukon - Except Diesel Engine). Scheme 13

Scheme 13: A/C Compressor Clutch Control Circuit Wiring Diagram ("C" & "K" Pickups, Escalade, Suburban, Tahoe & Yukon - Except Diesel Engine)
Scheme 13: A/C Compressor Clutch Control Circuit Wiring Diagram ("C" & "K" Pickups, Escalade, Suburban, Tahoe & Yukon - Except Diesel Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram ("C" & "K" Pickups, Suburban, Tahoe & Yukon - Diesel Engine). Scheme 14

Scheme 14: A/C Compressor Clutch Control Circuit Wiring Diagram ("C" & "K" Pickups, Suburban, Tahoe & Yukon - Diesel Engine)
Scheme 14: A/C Compressor Clutch Control Circuit Wiring Diagram ("C" & "K" Pickups, Suburban, Tahoe & Yukon - Diesel Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram (DeVille & Eldorado). Scheme 15

Scheme 15: A/C Compressor Clutch Control Circuit Wiring Diagram (DeVille & Eldorado)
Scheme 15: A/C Compressor Clutch Control Circuit Wiring Diagram (DeVille & Eldorado)

A/C Compressor Clutch Control Circuit Wiring Diagram ("G" 1500/3500, Express & Savana - Except Diesel Engine). Scheme 16

Scheme 16: A/C Compressor Clutch Control Circuit Wiring Diagram ("G" 1500/3500, Express & Savana - Except Diesel Engine)
Scheme 16: A/C Compressor Clutch Control Circuit Wiring Diagram ("G" 1500/3500, Express & Savana - Except Diesel Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram ("G" 2500/3500, Express & Savana - Diesel Engine). Scheme 17

Scheme 17: A/C Compressor Clutch Control Circuit Wiring Diagram ("G" 2500/3500, Express & Savana - Diesel Engine)
Scheme 17: A/C Compressor Clutch Control Circuit Wiring Diagram ("G" 2500/3500, Express & Savana - Diesel Engine)

A/C Compressor Clutch Control Circuit Wiring Diagram (Grand Prix). Scheme 18

Scheme 18: A/C Compressor Clutch Control Circuit Wiring Diagram (Grand Prix)
Scheme 18: A/C Compressor Clutch Control Circuit Wiring Diagram (Grand Prix)

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

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

A/C Compressor Clutch Control Circuit Wiring Diagram (Lumina & Monte Carlo). Scheme 20

Scheme 20: A/C Compressor Clutch Control Circuit Wiring Diagram (Lumina & Monte Carlo)
Scheme 20: A/C Compressor Clutch Control Circuit Wiring Diagram (Lumina & Monte Carlo)

A/C Compressor Clutch Control Circuit Wiring Diagram (Montana, Silhouette & Venture). Scheme 21

Scheme 21: A/C Compressor Clutch Control Circuit Wiring Diagram (Montana, Silhouette & Venture)
Scheme 21: A/C Compressor Clutch Control Circuit Wiring Diagram (Montana, Silhouette & Venture)

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

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

A/C Compressor Clutch Control Circuit Wiring Diagram (Sonoma & S10 Pickup - 2.2L VIN 4 Engine). Scheme 23

Scheme 23: A/C Compressor Clutch Control Circuit Wiring Diagram (Sonoma & S10 Pickup - 2.2L VIN 4 Engine)
Scheme 23: A/C Compressor Clutch Control Circuit Wiring Diagram (Sonoma & S10 Pickup - 2.2L VIN 4 Engine)