HVAC System - Manual - Troubleshooting Cadillac DeVille Concours I final

MODEL IDENTIFICATION

Note. This article does not cover Metro, Prizm or Saturn. For these models, see appropriate MANUAL A/C-HEATER SYSTEM article.

BODY DESIGNATION

SERIES DESIGNATION

OPERATIONAL TESTING

When trouble shooting and diagnosing an air conditioning system, always refer to appropriate vacuum diagram (if available) and wiring diagrams for the system involved. See appropriate MANUAL A/C-HEATER SYSTEMS article.

Electrical circuits are functioning properly if blower operates at all speeds and compressor clutch engages. If evaporator inlet pipe and accumulator surface appear to be the same temperature when felt by hand, system is properly charged with refrigerant. Ensure vacuum diaphragms and/or electric servo motors function properly when moving mode selector control.

BLOWER MOTOR WILL NOT RUN

Check fuses. Turn ignition switch to RUN position. Check for voltage at function control switch. Place blower switch in HI position. Check for voltage at switch and at high-speed blower relay. Ground blower motor ground circuit with ignition switch in ON position. If blower operates, motor is okay.

BLOWER DOES NOT OPERATE IN HI

Check for voltage at high-speed blower relay with ignition switch in ON position and blower switch in HI position. If voltage is not present, check for voltage at blower switch.

BLOWER OPERATES ONLY IN HI

Check blower resistors for open condition. Check blower switch for voltage at each position.

A/C DOES NOT WORK

With engine running and function control switch at A/C or NORM position, check for voltage at pressure cycling switch. Check for voltage between pressure cycling switch and A/C compressor clutch. Ground A/C compressor clutch circuit. If A/C clutch engages, check wide-open throttle cut-out switch and A/C compressor cut-off switch.

HEATER OUTPUT TEMPERATURE CHECK

1. Select heater (floor) mode, high temperature setting and high blower speed. Idle engine for about 20 minutes or until engine reaches normal operating temperature.
2. Drive vehicle at 30 MPH (48 KM/H). Measure ambient air temperature and floor outlet air temperature. If floor outlet air temperature exceeds minimum specification, heater output temperature is considered sufficient. See «HEATER OUTPUT TEMPERATURE MINIMUM SPECIFICATIONS»(/cadillac/deville-concours/i-final-1999-1999/remont/manual-hvac-system/#hvac-system-manual-troubleshooting) table.

HEATER OUTPUT TEMPERATURE MINIMUM SPECIFICATIONS

FUNCTIONAL TEST

1. Idle engine for about 20 minutes, until warm, or until thermostat opens. Ensure coolant temperature is about 194°F (90°C). Select bi-level mode. Move temperature lever to coldest temperature setting. Select high blower speed. Air should exit all outlets and should be about the same temperature as outside air.
2. Select vent mode. Air should exit vent outlets and should be about the same temperature as outside air. Air should not exit floor, defrost, or window defogger outlets.
3. Select heater (floor) mode. Most air should exit floor outlets, with remaining air exiting defrost and window defogger outlets. Air should not exit vent outlets. Air should be about the same temperature as outside air.
4. Select blend (floor-defrost) mode. An equal volume of air should exit defrost and floor outlets, with some air exiting side window defogger outlets.
5. Select defrost mode. Most air should exit defrost outlets, with a low volume of air exiting floor outlets.
6. Select bi-level mode. Move temperature lever to maximum hot setting. Air should exit vent outlets and its temperature should rapidly increase to about 131°F (55°C) or greater. For more precise heater output temperature check, see «HEATER OUTPUT TEMPERATURE CHECK»(/cadillac/deville-concours/i-final-1999-1999/remont/manual-hvac-system/#hvac-system-manual-troubleshooting__heater-output-temperature-check) . Defrost nozzle airflow volume should diminish and floor outlet airflow volume may increase slightly.
7. Move temperature lever to maximum cold setting. Air temperature should decrease to about the same temperature as outside air.
8. Slowly turn blower motor speed control knob toward OFF position, stopping briefly at each intermediate position to check force of airflow exiting instrument panel center outlets to hear blower noise. Airflow and blower noise should decrease noticeably at each intermediate position.

INSUFFICIENT HEATING

Insufficient heating may be caused by any of the following conditions

1. Low coolant level.
2. Loose or worn coolant pump drive belt.
3. Partially or fully clogged heater core or heater hose.
4. Obstruction to air circulation.
5. An air leak into passenger compartment.

1. Inspect cooling system and components for any of the conditions listed above. Repair as necessary. If no system faults are detected at this time, go to next step.
2. Place heater controls to heat mode. Place blower speed control to highest setting. Place temperature control to full warm position. Start engine and allow to idle. Inspect floor air outlet. If there is a high airflow, go to next step. If there is not a high airflow, go to step 15 .
3. Inspect blower speed for airflow change with changes in blower speed switch. If airflow changes in relation to blower switch change, system is okay at this time. If airflow does not change with changes in blower speed switch position, go to next step.
4. Inspect blower speed switch and/or blower motor resistor. Repair or replace as necessary. Check for heater output. See «HEATER OUTPUT TEMPERATURE CHECK»(/cadillac/deville-concours/i-final-1999-1999/remont/manual-hvac-system/#hvac-system-manual-troubleshooting__heater-output-temperature-check) . If heater output check is okay, go to next step. If heater output is not correct, go to step 6 .
5. Inspect vehicle for air leaks at the cowl, heater case, and vents. Inspect under the seat for obstructions.
6. Turn ignition on. Place blower on low speed setting. Place temperature control to mid-position. Rapidly move temperature control to full hot position. Listen for slam of temperature door. If slam of door is not heard, go to next step. If temperature door slam is heard, go to step 8 .
7. Inspect temperature control cable for correct adjustment. See appropriate ADJUSTMENTS article. Adjust, repair or replace as necessary.
8. Place temperature to full warm position. Start vehicle. Check temperature of heater inlet and outlet hoses by feel. If inlet hose is warmer than outlet hose, go to step 12 . If inlet hose is not warmer than outlet hose, go to next step.
9. Back flush heater core. Drain and refill cooling system. Retest heater system operation. See «HEATER OUTPUT TEMPERATURE CHECK»(/cadillac/deville-concours/i-final-1999-1999/remont/manual-hvac-system/#hvac-system-manual-troubleshooting__heater-output-temperature-check) .
10. Repeat heater test. See «HEATER OUTPUT TEMPERATURE CHECK»(/cadillac/deville-concours/i-final-1999-1999/remont/manual-hvac-system/#hvac-system-manual-troubleshooting__heater-output-temperature-check) . If symptoms still exist, go to next step.
11. Replace heater core.
12. Check thermostat for proper installation and seating. If thermostat is properly installed, go to step 14 .
13. Replace thermostat.
14. Remove, inspect, and install thermostat properly.
15. Perform functional check. See «FUNCTIONAL CHECK»(/cadillac/deville-concours/i-final-1999-1999/remont/manual-hvac-system/#hvac-system-manual-troubleshooting__functional-test) .
16. Inspect airflow from defroster and vent outlets. If airflow from these outlets is good, go to next step. If airflow from these outlets is poor, go to step 18 .
17. Inspect vacuum system of A/C-heater system. Repair as necessary.
18. Place mode control to defrost position. If airflow is coming from defroster outlets, go to next step. If airflow is not coming from defroster outlets, go to step 20 .
19. Inspect floor air outlet for obstructions.
20. Check for changes in airflow velocity, in relation to changes in blower speed setting.
21. Inspect blower inlet for obstructions. Repair as necessary. If no obstructions exist, go to next step.
22. Place blower on high speed setting. Move temperature control from full warm to full cold position, while listening for change in airflow. If there is a change in speed of airflow, go to next step. If there is no change in airflow speed, go to step 24 .
23. Inspect for obstruction between blower and system outlets. Repair as necessary.
24. Inspect temperature control valve, temperature control cable, and other temperature control components. Repair as necessary.

INSUFFICIENT COOLING (V5 TXV/VDOT SYSTEMS)

Note. Quick check procedure may be used to check for proper refrigerant charge, provided ambient temperature is more than 70°F (21°C). On vehicles with Cycling Clutch Orifice Tube (CCOT) system, compressor will cycle on and off to meet system requirements.

Quick Check Procedure

1. Ensure engine is at normal operating temperature. Open vehicle doors and hood. Select MAX A/C or RECIRC mode. Move temperature lever to COLD position. Blower switch in HIGH position. Engine should be at normal idle speed.
2. While compressor is engaged, feel temperature of accumulator surface and evaporator inlet pipe. If temperature of both components is the same, system is normal. If evaporator inlet pipe is frosted or feels cooler than accumulator surface, refrigerant charge is low.
3. Add refrigerant in 4-ounce increments, allowing system to stabilize between refrigerant additions, until accumulator and inlet pipe are the same temperature. Add an additional 14 ounces of refrigerant.

Thorough Check Procedure

See V5/TXV SYSTEM DIAGNOSIS or V5/VDOT SYSTEM DIAGNOSIS . For adjustments, diagnosis, or removal and installation procedures, go to appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article.

INSUFFICIENT COOLING (CCOT SYSTEMS)

Note. Ambient temperature is above 50°F (10°C) before performing diagnosis.

1. Inspect fuses, wire connectors, and blower fan operation of the A/C system. Repair faults as necessary. If system is okay, go to next step.
2. Inspect A/C compressor drive belt. If belt is in good condition and operating properly, go to next step. If belt is damaged, loose or missing, go to step 4 .
3. Start engine and allow to idle. Turn A/C on and place mode to VENT position. Place blower motor switch to highest speed setting. Observe A/C compressor clutch operation for 5 minutes. If A/C compressor clutch engages or cycles, go to step 7 . If A/C compressor clutch does not engage, go to step 11 .
4. Ensure the A/C compressor is not seized. If A/C compressor is seized, go to next step. If A/C compressor is not seized, go to step 6 .
5. Replace A/C compressor and orifice tube. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article. Evacuate and charge A/C system. Check for leaks.
6. Tighten or replace A/C compressor belt as necessary. Go to step 3 .
7. Feel the liquid refrigerant line before the orifice tube. If the orifice tube is cold, go to next step. If liquid orifice tube is not cold, go to step 9 .
8. Inspect high-side refrigerant line for frost spot or location of a restriction. Repair as necessary. Evacuate and charge A/C system. Check for leaks.
9. Feel evaporator inlet refrigerant tube. Feel evaporator outlet refrigerant tube. If inlet tube is cooler than outlet tube, go to next step. If inlet tube is not cooler than outlet tube, go to step 24 .
10. Conduct a leak test of refrigerant system. Repair as necessary. Evacuate and charge A/C system. Check for leaks.
11. Connect a fused jumper wire from A/C compressor clutch lead to positive battery terminal. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, go to step 18 .
12. Remove fused jumper wire. Inspect refrigerant pressure at accumulator fitting. If pressure is less than 50 psi (3.5 kg/cm 2 ), go to next step. If pressure is greater than specified value, go to step 15 .
13. Inspect refrigerant high-side pressure reading. If pressure is less than 50 psi (3.5 kg/cm 2 ), go to next step. If pressure is greater than specified value, go to step 10 .
14. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Locate and repair or replace restriction in high-side of refrigerant system or orifice tube. Evacuate and charge A/C system.
15. Connect a fused jumper wire between pressure switch and positive battery terminal. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, go to step 17 .
16. Replace A/C pressure switch. Check Schrader valve for leaks.
17. Inspect A/C pressure switch and wiring for an open or shorted condition. Repair as necessary.
18. Apply an external ground to A/C compressor clutch. If A/C compressor clutch engages, repair compressor ground circuit as necessary. If A/C compressor clutch does not engage while grounding compressor, go to next step.
19. Replace A/C compressor clutch or A/C compressor.
20. Add 16 ounces of refrigerant to system. Start vehicle and inspect A/C compressor clutch cycling. If A/C compressor clutch cycles more than 8 times per minute, go to next step. If A/C compressor clutch does not cycle more than 8 times per minute, go to step 22 .
21. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Inspect for a plugged orifice tube. Repair as necessary. Evacuate and charge A/C system.
22. Feel evaporator inlet refrigerant tube. Feel evaporator outlet refrigerant tube. If inlet tube is cooler than outlet tube, go to next step. If inlet tube is not cooler than outlet tube, system is okay at this time.
23. Add 16 ounces of refrigerant to system. Feel evaporator inlet refrigerant tube. Feel evaporator outlet refrigerant tube. If inlet tube is cooler than outlet tube, go to next step. If inlet tube is not cooler than outlet tube, system is okay at this time.
24. Install manifold gauge set. Check A/C compressor clutch cycling pressure. If A/C compressor cycles ON within 41-51 psi (2.9-3.6 kg/cm 2 ), go to next step. If A/C compressor does not cycle on within specified range, go to step 27 .
25. Check A/C compressor clutch cycling pressure. If A/C compressor cycles OFF within 20-28 psi (1.4-2.0 kg/cm 2 ), go to next step. If A/C compressor does not cycle of within specified range, go to step 27 .
26. Start engine and allow to idle. Turn A/C on. Place mode to upper vents position. Place blower motor switch to MAX position. Close all windows and doors of vehicle. Install a thermometer in center vent outlet. Stabilize engine speed for 5 minutes. Compare thermometer temperature reading with «A/C SYSTEM PERFORMANCE»(/cadillac/deville-concours/i-final-1999-1999/remont/manual-hvac-system/#hvac-system-manual-troubleshooting) table. If temperature reading is within limits, system is okay at this time. If readings are not within limits, go to step 31 . A/C SYSTEM PERFORMANCE Relative Humidity Ambient Temp. °F (°C) Max Outlet Temp. °F (°C) 20% 70 (21.1) 42 (5.6) 80 (26.7) 44 (6.7) 90 (32.2) 50 (10.0) 100 (37.8) 52 (11.1) 30% 70 (21.1) 44 (6.7) 80 (26.7) 48 (8.9) 90 (32.2) 54 (12.2) 100 (37.8) 58 (14.4) 40% 70 (21.1) 46 (7.8) 80 (26.7) 50 (10.0) 90 (32.2) 58 (14.4) 100 (37.8) 64 (17.8) 50% 70 (21.1) 48 (8.9) 80 (26.7) 54 (12.2) 90 (32.2) 60 (15.6) 100 (37.8) 70 (21.1) 60% 70 (21.1) 50 (10.0) 80 (26.7) 56 (13.3) 90 (32.2) 64 (17.8) 100 (37.8) 74 (23.3) 70% 70 (21.1) 52 (11.1) 80 (26.7) 60 (15.6) 90 (32.2) 66 (18.9) 80% 70 (21.1) 54 (12.2) 80 (26.7) 62 (16.7) 90 (32.2) 70 (21.1) 90% 70 (21.1) 55 (13.3) 80 (26.7) 64 (17.8)
27. If A/C compressor clutch cycles ON above 51 psi (3.6 kg/cm 2 ), go to next step. If A/C compressor clutch does not cycle ON above specified pressure, go to step 29 .
28. If A/C compressor clutch cycles OFF below 20 psi (1.4 kg/cm 2 ), go to step 16 . If A/C compressor clutch does not cycle OFF below 20 psi. (1.4 kg/cm 2 ), go to next step.
29. Disconnect blower motor connector. Determine at what pressure A/C compressor clutch cycles OFF. If A/C compressor clutch cycles OFF below 20 psi (1.4 kg/cm 2 ), go to step 16 . If A/C compressor clutch does not cycle OFF below 20 psi (1.4 kg/cm 2 ), go to next step.
30. Connect blower motor connector. Go to step 26 .
31. Observe A/C compressor clutch cycling. If A/C compressor clutch cycles continuously, go to next step. If A/C compressor clutch does not continuously cycle, go to step 21 .
32. Discharge A/C system, using approved refrigerant recovery/recycling equipment. If orifice tube is missing, go to next step. If orifice tube is installed, go to step 34 .
33. Replace orifice tube. Evacuate and charge A/C system. Check for leaks.
34. Inspect suction line for restriction. If suction line is restricted, go to next step. If suction line is okay, go to step 36 .
35. Repair suction line as necessary. Go to next step.
36. Evacuate and charge A/C system. Ensure A/C system is operating properly.

Preliminary Checks

Check and repair the following

1. Connect Tech 1 scan tool to Data Link Connector (DLC). Check for stored trouble codes. If codes are found, see appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article or appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
2. Check A/C fuse(s).
3. Check A/C blower operation.
4. On vehicles with cable operated temperature door, move temperature lever rapidly from cold to hot. Listen for temperature door hitting travel stops at each end. Adjust as necessary.
5. Check A/C compressor clutch coil connection.
6. Check A/C pressure transducer connection.
7. Check A/C compressor belt condition. Adjust or replace as necessary.
8. Check cooling fan operation.
9. Check for restricted airflow across condenser.
10. Check Technical Service Bulletins (TSBs) for A/C system updates.

Diagnostic Procedure

1. Perform preliminary inspection. Repair as necessary. Go to next step.
2. Turn ignition off. Inspect A/C, heater, and ignition fuses. Replace as necessary. Set parking brake. Start engine. Set blower speed switch to any position except off. Turn A/C compressor on. Turn blower speed switch off. Turn ignition off. Inspect fuses again. If any or all fuses are now blown, go to step 20 . If fuses are okay, go to next step.
3. Turn ignition on. While listening to blower motor, turn blower speed switch through each speed setting, and back to off. If blower motor speed increased and decreased in relation to blower speed selection, go to next step. If blower speed does not change with blower switch setting, go to step 21 .
4. While monitoring temperature door operation, move temperature control from COLD to HOT and back to COLD position. If temperature door operates from cold to hot positions, go to next step. If temperature door does not operate with changes in temperature setting, go to step 22 .
5. Inspect for loose, damaged or missing A/C compressor drive belt. Replace as necessary. If drive belt is okay, go to next step.
6. Ensure engine cooling fan is operating properly. Repair as necessary. If engine cooling fan is operating properly, go to next step.
7. Inspect condenser for restriction in airflow. Clean, repair, or replace as necessary. If airflow across condenser is okay, go to next step.
8. Ensure ambient air temperature is greater than 60°F (16°C) before continuing. Start engine. Set mode selector to VENT position. Set blower speed to highest speed. Set temperature selector to full COLD position. Turn A/C on. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, go to step 11 .
9. Monitor compressor for any unusual knocking, moaning, or drive belt slipping noises. Cycle A/C compressor clutch off and on to verify noise is from compressor. If A/C compressor noise is excessive, go to step 23 . If A/C compressor is not making any excessive noises, go to next step.
10. Feel the liquid refrigerant line between condenser and receiver/drier (should feel warm). If liquid refrigerant line feels cool or cold, go to step 24 . If line feels warm, go to step 14 .
11. Turn ignition off. Install a manifold gauge set to A/C system. Both readings should be equal at about 50 psi (3.5 kg/cm 2 ) or greater. If readings are as described, go to step 25 . If readings are not as described, go to next step.
12. Monitor low-side and high-side pressure readings of manifold gauge set. If readings are 10-50 psi (.7-3.5 kg/cm 2 ), go to next step.
13. Add 16 ounces of refrigerant to A/C system. Check A/C system for leaks. If a refrigerant leak is found, go to step 26 . If a leak in A/C system cannot be found, go to step 28 .
14. Feel evaporator inlet line (small tube) and evaporator outlet line near evaporator. Evaporator inlet line should feel warm. If evaporator inlet line feels cooler than outlet line, go to next step. If inlet does not feel cooler than outlet, go to step 18 .
15. Inspect A/C system for leaks. If a refrigerant leak is found, go to step 26 . If a leak in A/C system cannot be found, go to next step.
16. Add 16 ounces of refrigerant to A/C system. Monitor A/C compressor clutch cycle rate. If A/C compressor clutch cycle rate is more than 8 cycles per minute, go to step 27 . If A/C compressor clutch cycle rate is less than 8 cycles per minute, go to next step.
17. Start engine. Set mode selector to VENT position. Set blower speed to highest speed. Set temperature selector to full COLD position. Turn A/C on. Feel evaporator inlet line (small tube) and evaporator outlet line near evaporator. If evaporator inlet line feels cooler than outlet line, go to step 27 . If inlet does not feel cooler than outlet, go to step 28 .
18. Inspect high-side pressure reading of manifold gauge set. If A/C compressor engages within 28-455 psi (2.0-32.0 kg/cm 2 ), go to next step. If A/C compressor does not engage within specified value, go to step 29 .
19. Run A/C compressor. Monitor A/C compressor clutch operation and high-side pressure reading for 5 minutes. The A/C compressor clutch should disengage if high-side pressure switch senses pressure outside the specified range of 28-455 psi (2.0-32.0 kg/cm 2 ). If A/C compressor remains engaged, go to step 29 . If A/C compressor disengages as described, go to step 30 .
20. Check A/C compressor clutch controls. See A/C COMPRESSOR CLUTCH CONTROLS article or appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article. Go to step 3 .
21. Check blower motor controls. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article. Go to step 4 .
22. Check A/C-heater system temperature control cable or linkage adjustments. See appropriate HEATER SYSTEMS or MANUAL A/C-HEATER SYSTEMS article.
23. Locate and repair cause of excessive A/C compressor noise. Repair as necessary. Go to step 10 .
24. Locate high-side refrigerant lines for frost spot in order to locate restriction in high-side of A/C system. Repair restriction in high-side portion of A/C system as necessary. Go to step 14 .
25. Check A/C-heater system control cable or linkage adjustments. See appropriate HEATER SYSTEMS or MANUAL A/C-HEATER SYSTEMS article. Go to step 9 .
26. Repair refrigerant leak as necessary. Evacuate and charge A/C system. Go to step 30 .
27. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Inspect for restriction in expansion valve or in high-side line of A/C system. Evacuate and charge A/C system. Go to step 30 .
28. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Evacuate and charge A/C system. Go to step 30 .
29. Replace A/C refrigerant pressure switch. Go to step 30 .
30. Check A/C system performance. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article.

Check and repair the following

1. Check A/C fuse(s).
2. Check A/C blower operation.
3. On vehicles with cable operated temperature door, move temperature lever rapidly from cold to hot. Listen for temperature door hitting travel stops at each end. Adjust as necessary.
4. Check clutch coil and connections at rear head pressure switch(es).
5. Check A/C compressor belt condition. Adjust or replace as necessary.
6. Check cooling fan operation.
7. Check for restricted airflow across condenser.
8. Check Technical Service Bulletins (TSBs) for A/C system updates.

If discharge air temperature with A/C on is normal after making repairs, system is operating properly. If further trouble shooting is required, go to appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article.

Scheme 1

1. Perform preliminary inspection. Repair as necessary. Go to next step.
2. Ensure ambient air temperature is greater than 60°F (16°C) before continuing. Turn ignition off. Connect manifold gauge set. If high-side and low-side pressures are equal, and readings are about 50 psi (3.5 kg/cm 2 ), go to step 7. If readings are not equal, or less than specified, go to next step.
3. Inspect A/C system for leaks. If a leak is found, go to step 5. If no leak is found in A/C system, go to next step.
4. If high-side and low-side readings are within 30-50 psi (2.1-3.5 kg/cm 2 ), system is okay at this time. If readings are not within specified range, go to next step.
5. Repair leak in A/C system. Go to next step.
6. Evacuate and charge A/C system. If system pressures are equal, and above 50 psi (3.5 kg/cm 2 ) system is okay at this time. If readings are not equal, and not greater than 50 psi (3.5 kg/cm 2 ), go to next step.
7. Allow engine to idle. Set A/C mode control to VENT position. Set blower speed to highest setting. Set temperature to full cold position. Turn A/C on. If A/C compressor engages, go to next step. If A/C compressor does not engage, go to step 16.
8. Inspect for excessive noise coming from A/C compressor area. If excessive noise is coming from A/C compressor or drive belt, go to next step. If there are no excessive noises, go to step 19.
9. Inspect A/C compressor drive belt for slippage. If noise from A/C compressor is due to drive belt slippage, go to next step. If A/C compressor drive belt is not slipping, go to step 11.
10. Replace A/C compressor drive belt. Retest A/C system operation.
11. Turn A/C on and off, to verify if noise is coming from A/C compressor. If noise is coming from A/C compressor, go to next step. If noise is not coming from A/C compressor, go to step 14.
12. Inspect A/C refrigerant lines for contact with components. If refrigerant lines are contacting other components, go to next step. If lines are not contacting any other components, go to step 14.
13. Reposition or replace refrigerant lines as necessary. Go to step 19.
14. If noise is coming from A/C compressor. go to next step. If noise is not coming from A/C compressor, go to step 19.
15. Replace A/C compressor. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article. If noise is still present, go to step 19.
16. Turn ignition off. Disconnect A/C compressor clutch connector. Using jumper wires, connect one A/C compressor clutch terminal to ground, and the other to battery positive. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, go to step 18.
17. Repair electrical circuit to A/C compressor clutch. Start engine and allow to idle. Set controls for maximum A/C delivery. If A/C compressor clutch engages, system is okay. If A/C compressor clutch does not engage, go to step 19.
18. Replace A/C compressor clutch coil. See COMPRESSOR SERVICING in GENERAL SERVICING.
19. Close all windows and doors of vehicle. Set A/C control panel to VENT position, blower speed to highest setting and temperature to full cold. Start engine and allow to idle for 5 minutes. Feel liquid refrigerant line on both sides of expansion (orifice) tube. If temperature feels the same on both side of expansion (orifice) tube, go to next step. If change in temperature can be felt from both sides of expansion (orifice) tube, go to step 25.
20. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Check for missing orifice tube. If expansion (orifice) tube is missing, go to next step. If orifice tube is not missing, go to step 22.
21. Install missing expansion (orifice) tube.
22. Inspect for restriction in high-side line or in orifice tube. If found, go to step 24.
23. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Check system for leaks. Evacuate and charge A/C system. Check A/C system for normal operation. If okay, system is okay at this time. If A/C system does not operate normally, go to step 25.
24. Repair restriction in high-side of A/C system as necessary. Evacuate and charge A/C system. Test system for normal operation.
25. Operate A/C system for 5 minutes or longer. Record high-side and low-side pressure readings when electric cooling fans are ON. Locate cross-section of high-side and low-side pressure readings on chart. (Scheme 1) If readings intersect on the right side of the chart, go to next step. If readings do not intersect on the right side of the chart, go to step 36.
26. Set mode selector to VENT position. Set blower speed to highest speed. Set temperature selector to full COLD position. Turn A/C on. Feel refrigerant line between condenser and expansion (orifice) tube. If liquid line feels cold, go to next step. If liquid line does not feel cold, go to step 31.
27. Check cooling fan operation. If cooling fans are operating, go to next step. If cooling fans are not operating, go to step 29.
28. Check for good airflow across condenser. If air flow is restricted, go to step 30. If airflow across condenser is okay, check A/C system performance. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article.
29. Repair cooling fans as necessary. Check A/C system performance.
30. Remove, repair, or replace as necessary to promote good airflow across condenser. Check A/C system performance.
31. Check refrigerant system for indication of overcharging. If system overcharged, go to next step. If system does not appear to be overcharged, go to step 33.
32. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Evacuate and charge A/C system. Check A/C system for normal operation.
33. Check for presence of air in A/C system. If air is found in A/C system, go to next step. If no air is present in A/C system, check A/C system for normal operation.
34. Leak test A/C system. If a leak is present, go to next step.
35. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Evacuate and charge A/C system. Check A/C system for normal operation.
36. With engine running, compare high-side and low-side readings. If readings are equal to about 30 psi (2.1 kg/cm 2 ), go to next step. If both readings are not equal to about 30 psi (2.1 kg/cm 2 ), go to step 42.
37. Close all doors and windows. Run engine at 2000 RPM. Set temperature to full cold. Set blower to highest setting. Cycle between VENT and A/C modes every 20 seconds for about 3 minutes. If pressure readings are equal to about 30 psi (2.1 kg/cm 2 ), go to next step.
38. Check for the following conditions: Slow rise in pressure readings of both high-side and low-side gauges. Compressor suction line is warm. Discharge line is very hot. If all these conditions exist, go to next step. If all of these conditions are not met, go to step 40.
39. Replace A/C compressor. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article.
40. Turn engine off. With A/C compressor clutch disengaged, check if compressor clutch drive (not pulley) turns freely by hand. If drive can be turned by hand, go to step 39. If drive cannot be turned freely, go to next step.
41. Check for a rapid rise in low-side pressure when engine is at 2000-2800 RPM. If there is a rapid rise in low-side pressure, go to step 52. If there is no rapid rise in low-side pressure, go to step 39.
42. If low-side pressure is between 27-38 psi (1.9-2.7 kg/cm 2 ), go to next step. If readings are not as specified, go to step 52.
43. If liquid line before expansion (orifice) tube is cold, go to next step. If liquid line is not cold, perform A/C system performance test.
44. Locate restriction in liquid line before expansion (orifice) tube. If restriction is found, go to next step.
45. Repair restriction in liquid line as necessary.
46. Add 16 ounces of refrigerant to A/C system. Check if cooling improves. If cooling improves, go to next step. If cooling does not improve, go to step 49.
47. Leak test A/C system. If a leak is found, go to next step.
48. Repair leak in A/C system. Evacuate and charge A/C system as necessary.
49. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Check for a plugged orifice tube. If orifice tube is plugged, go to next step.
50. Clean or replace orifice tube. Go to next step.
51. Evacuate and charge A/C system. Check A/C system for normal operation.
52. Connect manifold gauge set. Close all windows and doors. Run engine at about 2000 RPM. Set mode control to VENT position. Set temperature to full cold position. Turn A/C on. Set blower speed to low setting. If low-side pressure is 25-35 psi (1.7-2.5 kg/cm 2 ), check A/C system performance. If readings are not as specified, go to next step.
53. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Using snap ring pliers, remove A/C compressor control valve retaining ring. Remove A/C compressor control valve. Replace A/C compressor control valve. Go to next step.
54. Evacuate and charge A/C system. Check A/C system for normal operation.

See also:
• HEATER OUTPUT TEMPERATURE MINIMUM SPECIFICATIONS
• HEATER OUTPUT TEMPERATURE CHECK
• FUNCTIONAL CHECK