Mechanics

CHEVY AC CLUTCH NOT ENGAGING

2000 Chevrolet Malibu

Air Conditioning problem
2000 Chevy Malibu 6 cyl Front Wheel Drive Automatic

my A/C and my radiator cooling fans quit working at about the same time.

the control relays are not getting turned on by the PCM.

If I provide the ground to the relay coils that the PCM usually provides both systems will run.

Could there be a common ground splice for the PCM and where is it at, OR is the PCM just bad?

PS
I do have trouble codes set for cooling fan control circuit malfunction and air conditioning relay control circuit
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Thousndlrbill
May 22, 2009.



4.3L: " M" & " L" SERIES NOTE: For circuit, wire color and terminal identification, see WIRING DIAGRAMS. Also see WIRING DIAGRAMS in appropriate MANUAL or AUTOMATIC A/C HEATER SYSTEMS article. NOTE: HVAC control assembly may be referred to as HVAC control module. 2000 vehicles use a Vehicle Control Module (VCM) and 2001 vehicles use a Powertrain Control Module (PCM). Description Regardless of selected A/C mode setting, a request is made to Powertrain Control Module (PCM)/Vehicle Control Module (VCM) to turn on A/C compressor clutch. Request is sent to PCM/VCM through A/C request signal circuit from HVAC control assembly. Power and ground is provided to HVAC control assembly by ignition voltage and ground circuits. PCM/VCM turns on A/C compressor by providing a path to ground through A/C clutch relay control circuit for A/C compressor clutch relay. Ignition voltage circuit provides power to A/C compressor clutch relay control. Once relay contact closes its internal switch, power from battery voltage circuit is provided to A/C compressor clutch through A/C compressor clutch supply voltage circuit. Whenever compressor is turned off, A/C compressor clutch diode prevents a voltage spike from entering vehicles electrical system. Ground circuit provides a pathway to ground for compressor. Both A/C request signal and A/C clutch relay control circuits are grounded internally within PCM/VCM. A/C system is protected by 2 pressure switches. A/C high pressure switch interrupts A/C request signal when A/C line pressure exceeds a predetermined value. A/C low pressure switch interrupts A/C low pressure switch signal when A/C line pressure drops below a predetermined value. When PCM/VCM stops receiving required signals, A/C compressor clutch relay control circuit is no longer grounded, thus shutting off compressor. Compressor Clutch Does Not Engage Ensure outside air temperature is greater than 38 °F (3 °C). Start engine. Turn blower motor switch to maximum speed position. Place mode switch in bi-level position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step. 1. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE-TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING. 2. If HVAC control assembly is inoperative, go to step 17. If HVAC control assembly is not inoperative, go to next step. 3. Page 1 of 4 A/C COMPRESSOR CLUTCH CONTROLS -2000 Chevrolet Malibu Start engine. Using scan tool, observe A/C REQUEST parameter. Place air temperature switch in coldest position. Place mode switch in bi-level position. If scan tool indicates A/C REQUEST parameter is ON, go to step 6. If scan tool does not indicate A/C REQUEST parameter is ON, go to next step. 4. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Connect fused jumper (3 amp) between A/C request circuits (Light Orange wire and Dark Green/White wire) at A/C high pressure switch connector. Start engine. Using scan tool, observe A/C REQUEST parameter. Place air temperature switch in coldest position. Place mode switch in bi-level position. If scan tool indicated A/C request parameter is ON, go to step 29. If scan tool does not indicate A/C REQUEST parameter is ON, go to step 23. 5. If scan tool indicates A/C LOW PRESSURE SWITCH parameter is CLOSED, go to step 8. If scan tool does not indicate A/C LOW PRESSURE SWITCH parameter is CLOSED, go to next step. 6. Turn ignition switch to OFF position. Disconnect A/C low pressure switch. Connect fused jumper (3 amp) between A/C low pressure switch signal circuit (Dark Green wire) and ground circuit (Black wire) at A/C low pressure switch connector. Start engine. Using scan tool, observe A/C LOW PRESSURE SWITCH parameter. If scan tool indicates A/C LOW PRESSURE SWITCH parameter is CLOSED, go to step 26. If scan tool does not indicate A/C LOW PRESSURE SWITCH is CLOSED, go to step 19. 7. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turn on and off with each command, go to step 14. If A/C compressor clutch relay does not turn on and off with each command, go to next step. 8. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 24. 9. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 25. If test light does not turn on and off with each command, go to next step. 10. If test light remains on with each command, go to step 13. If test light does not remain on with each command, go to next step. 11. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to step 30. 12. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to step 30. 13. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit (Orange wire) of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 16. 14. Connect fused jumper (10 amp) between switch side voltage circuit (Orange wire) of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 25. If A/C compressor clutch does not engage, go to step 21. 15. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 37. 16. Check ignition voltage circuit (Brown wire) of HVAC control assembly for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to next step. 17. Check ground circuit (Black wire) of HVAC control assembly for open. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to step 28. 18. Check A/C low pressure switch signal circuit (Dark Green wire) for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to step 20. 19. Check ground circuit (Black wire) of A/C low pressure switch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to step 30. 20. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to next step. 21. Check ground circuit (Black wire) of A/C compressor clutch for high resistance or open. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to step 27. 22. Turn ignition switch to OFF position. Reconnect A/C high pressure switch. Check A/C request signal circuit (Light Green wire and Dark Green/White wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to step 30. 23. Repair coil side voltage supply circuit (Pink wire) of A/C compressor clutch relay. After repairs, go to step 37. 24. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to step 31. 25. Check A/C low pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to step 32. 26. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to step 34. At the harness connector of the A/C compressor clutch. 27. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to step 35. 28. Check A/C high pressure switch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to step 33. 29. Check PCM/VCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 37. If problem was not found, go to step 36. 30. Replace A/C compressor clutch relay. After repairs, go to step 37. 31. Replace A/C low pressure switch. After repairs, go to step 37. 32. Replace A/C high pressure switch. After repairs, go to step 37. 33. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 37. 34. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 37. 35. Replace PCM/VCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step. 36. Operate system to verify repair. 37. Compressor Clutch Does Not Disengage Start engine. Place blower motor switch in OFF position. Place mode switch in OFF position. If A/C compressor operates, go to next step. If A/C compressor does not operate, problem is intermittent. 1. Using scan tool, observe A/C REQUEST parameter in POWERTRAIN data list. If scan tool indicates A/C REQUEST parameter is ON, go to next step. If scan tool does not indicate A/C REQUEST parameter in ON, go to step 5. 2. Check A/C request signal circuit (Light Green wire and Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to next step. 3. Turn ignition switch to OFF position. Disconnect A/C high pressure switch. Start engine. Using scan tool, observe A/C REQUEST parameter. If scan tool indicates A/C REQUEST parameter is ON, go to step 11. If scan tool does not indicate A/C REQUEST parameter is ON, go to step 10. 4. Remove A/C compressor clutch relay. If A/C compressor clutch turns off, go to next step. If A/C compressor clutch does not turn off, go to step 8. 5. Measure resistance between switch side A/C compressor clutch relay terminals. If resistance is infinite, go to next step. If resistance is not infinite, go to step 9. 6. Check A/C clutch relay control circuit (Dark Green/White wire) for short to ground. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 11. 7. Check A/C compressor clutch supply voltage circuit (Dark Green wire) for short to voltage. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 13. 8. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 12. 9. Check HVAC control assembly connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 14. 10. Check PCM/VCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 16. If problem was not found, go to step 15. 11. Replace A/C compressor clutch relay. After repairs, go to step 16. 12. Replace A/C compressor clutch. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 16. 13. Replace HVAC control assembly. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 16. 14. Replace PCM/VCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step. 15. Operate system to verify repair. 16.
5/23/2009

Merlin2021
May 23, 2009.
I have a 2000 Malibu and cannot find a low pressure switch for it, could you tell me where it is, I have looked at the accumulator and it is not on there, it has a high pressure switch on the high side line. I am not getting the ground to the relay coil that energizes the ground for the compressor, when I take a wire and ground it connected to the ground of the relay coil, my compressor comes on, I know that it has enough Freon in it, I have checked the pressures.
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Tiny
Uhsnoebird
Apr 13, 2014.

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