Test the diode for cotinuity, should work one way only, this protects from voltage spikes as the clutch energizes, and each time it turns on it also causes a spike. Check gree/white stripe wire for short to grond beteen compressor and PCM. Description Compressor for air conditioning system is belt-driven by engine through A/C compressor clutch. Clutch allows compressor to engage for A/C and defroster operation, disengage when air conditioning is not requested and disengage when engine load must be reduced. Battery voltage is supplied to powertrain control module (PCM) when heater and A/C control mode selector knob is in MAX A/C, NORM A/C, BI-LEVEL, DEFOG or DEFROST modes. Voltage signal tells PCM that A/C compressor operation is requested. Under normal operating conditions, PCM supplies a ground to relay coil of A/C compressor control. Relay energizes. Voltage is supplied to A/C compressor clutch through relay center fuse. A/C compressor clutch engages. Compressor runs. If PCM determines engine load should be reduced, such as during full throttle conditions, PCM de-energizes A/C compressor control relay in order to disengage compressor clutch. De-energization occurs even though voltage signal from heater and A/C control is still present. Diode of A/C compressor clutch connects across terminals of A/C compressor clutch. Diode provides a path for current which results from voltage spikes. Voltage spikes generate from collapsing magnetic field of A/C compressor clutch coil. Voltage spikes occur every time coil de-energizes. Diagnostic System Check 1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article. 2. Turn ignition on, engine off. Try to establish scan tool communication with Powertrain Control Module (PCM). If communication with PCM is established, go to next step. If communication with PCM is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article. 3. Select display DTC function for PCM. Record all displayed DTCs and status of displayed DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see COMPRESSOR CLUTCH DOES NOT ENGAGE or COMPRESSOR CLUTCH DOES NOT DISENGAGE. 4. If scan tool does not display DTCs beginning with "U", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with "U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article. Compressor Does Not Engage 1. If diagnostic system check has not been performed, see DIAGNOSTIC SYSTEM CHECK. If diagnostic system check has been performed, go to next step. 2. Ensure outside air temperature is greater than 38 °F (3 °C). Start engine. Turn blower motor switch to maximum speed position. Place A/C switch in ON position. Place air temperature control switch in coldest position. If A/C compressor operates, problem is intermittent. If A/C compressor does not operate, go to next step. 3. Park vehicle inside or in shade. Open windows in order to ventilate interior of vehicle. If A/C system was operating, then allow A/C system to equalize for about 2 minutes. Turn ignition switch to OFF position. Install Refrigerant Station (J 43600 ACR 2000). Record outside air temperature at vehicle. Record readings of low and high side static pressures. Compare pressure values with specifications for ambient air temperature. See PRESSURE- TEMPERATURE RELATIONSHIP article in GENERAL SERVICING. If pressure values are within specification for ambient air temperature and within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If pressure values are not within specification for ambient air temperature or within 15 psi (1.1 kg/cm 2 ) of each other, see LEAK TESTING article in GENERAL SERVICING. 4. Turn ignition switch to ON position, with engine off. Using scan tool, observe A/C HIGH SIDE PRESSURE SENSOR parameter in POWERTRAIN data list. Compare A/C high side pressure on scan tool to high side pressure value on refrigerant station. If high side pressure values are within 15 psi (1.1 kg/cm 2 ) of each other, go to next step. If high side pressure values are not within 15 psi (1.1 kg/cm 2 ) of each other, go to step 18. 5. If HVAC control module is inoperative, go to step 17. If HVAC control module is not inoperative, go to next step. 6. Start engine. Using scan tool, observe A/C REQUEST parameter in ENGINE DATA 2 data list. Turn air temperature switch to coldest position. Turn blower motor to ON position. Place A/C request switch in ON position. If scan tool indicates A/C REQUEST parameter is ON, go to step 11. If scan tool does not indicate A/C REQUEST parameter is ON, go to next step. 7. If A/C request indicator illuminates, go to step 9. If A/C request indicator does not illuminate, go to next step. 8. Ensure blower motor switch is in ON position. Turn ignition switch to ON position. Check blower motor off circuit (Dark Green wire) at HVAC control assembly for short to voltage. If problem was found, repair as necessary. After repairs, go to step 36. If problem was not found, go to step 29. 9. Turn ignition switch to OFF position. Disconnect PCM. Turn ignition switch to ON position, with engine off. Turn air temperature switch to coldest position. Turn blower motor switch to maximum speed position. Place A/C request switch in ON position. Measure voltage between A/C request signal circuit (Dark Green/White wire) of PCM and ground. If voltage is 10-12.5 volts, go to step 30. If voltage is not 10-12.5 volts, go to next step. 10. Turn ignition switch to OFF position. Check A/C request signal circuit (Dark Green/White wire) for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 36. If problem was not found, go to step 29. 11. Using scan tool, command A/C compressor clutch relay on and off. If A/C compressor clutch relay turns on and off with each command, go to step 15. If A/C compressor clutch relay does not turn on and off with each command, go to next step. 12. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Turn ignition switch to ON position, with engine off. Using test light connected to ground, probe coil side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 25. 13. Connect test light between control circuit (Dark Green/White wire) of A/C compressor clutch relay and coil side voltage supply circuit of A/C compressor clutch relay. Using scan tool, command A/C compressor clutch relay on and off. If test light turns on and off with each command, go to step 27. If test light does not turn on and off with each command, go to next step. 14. If test light remains on with each command, go to step 21. If test light does not remain on with each command, go to step 20. 15. Turn ignition switch to OFF position. Disconnect A/C compressor clutch relay. Using test light connected to ground, probe switch side voltage supply circuit of A/C compressor clutch relay. If test light is on, go to next step. If test light is off, go to step 24. 16. Connect fused jumper (10 amp) between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit (Dark Green wire) of A/C compressor clutch. Turn ignition switch to ON position, with engine off. If A/C compressor clutch engages, go to step 27. If A/C compressor clutch does not engage, go to step 22. 17. Test ignition voltage circuit (Brown wire) of HVAC control module for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 36. If problem was not found, go to step 19. 18. Check ground circuit (Black wire) of A/C refrigerant pressure sensor for open. If problem was found, repair as necessary. After repairs, go to step 36. If problem was not found, go to step 26. 19. Check ground circuit (Black wire) of HVAC control module for open. If problem was found, repair as necessary. After repairs, go to step 36. If problem was not found, go to step 29. 20. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for open. If problem was found, repair as necessary. After repairs, go to step 36. If problem was not found, go to step 30. 21. Check control circuit (Dark Green/White wire) of A/C compressor clutch relay for short to ground. If problem was found, repair as necessary. After repairs, go to step 36. If problem was not found, go to step 30. 22. Check A/C compressor clutch supply voltage circuit (Dark Green wire) at A/C compressor clutch for short to ground, high resistance, or open. If problem was found, repair as necessary. After repairs, go to step 36. If problem was not found, go to next step. 23. Check ground circuit (Black wire) of A/C compressor clutch for a high resistance or open. If problem was found, repair as necessary. After repairs, go to step 36. If problem was not found, go to step 28. 24. Repair switch side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 36. 25. Repair coil side voltage supply circuit of A/C compressor clutch relay. After repairs, go to step 36. 26. Check A/C refrigerant pressure sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 36. If problem was not found, go to step 31. 27. Check A/C compressor clutch relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 36. If problem was not found, go to step 32. 28. Check A/C compressor clutch connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 36. If problem was not found, go to step 33. 29. Check HVAC control module connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 36. If problem was not found, go to step 34. 30. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step 36. If problem was not found, go to step 35. 31. Replace A/C refrigerant pressure sensor. After repairs, go to step 36. 32. Replace A/C compressor clutch relay. After repairs, go to step 36. 33. Replace A/C compressor clutch coil. See appropriate COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs, go to step 36. 34. Replace HVAC control module. See REMOVAL & INSTALLATION in appropriate MANUAL A/C-HEATER SYSTEMS article. After repairs, go to step 36. 35. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. After repairs, go to next step. 36. Operate system to verify repair.
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Saturday, September 5th, 2009 AT 1:36 PM
