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Home >> Chevrolet >> 1997 >> Astro Van Passenger, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing 4.3L >> Miscellaneous Pcm/VCM Controls >> A/C Clutch Circuit Diagnosis >> Compressor Clutch Control Circuit Diagnosis

Compressor Clutch Control Circuit Diagnosis

  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 on A/C. If A/C compressor clutch engages, then disengages within 60 seconds, diagnose A/C-heater system. If operation is not as specified, go to next step.
  3. Install scan tool. With A/C on, monitor A/C REQUEST. 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 8).
  4. Disconnect A/C compressor clutch harness connector. Connect a test light between harness connector terminals. If test light comes on, go to next step. If test light does not come on, go to step 12).
  5. Check for faulty A/C compressor clutch harness connections. If a problem is found, go to next step. If no problem is found, go to step 7).
  6. Repair faulty A/C compressor clutch wire harness connections. Go to step 27).
  7. Replace A/C compressor clutch. Go to step 27).
  8. Turn ignition off. Disconnect VCM harness connectors. Turn ignition on. Using a test light connected to ground, probe A/C request circuit (Dark Green/White wire) at VCM harness connector. If test light comes on, go to next step. If test light does not come on, go to step 11).
  9. Check for poor VCM harness connections. If a problem is found, go to next step. If no problem is found, go to step 26).
  10. Repair VCM harness connector. Go to step 27).
  11. Repair open or short to ground in Dark Green/White wire between VCM and A/C control switch. Go to step 27).
  12. 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 14).
  13. Repair open in A/C compressor clutch ground circuit (Black wire) between harness connector and ground. Go to step 27).
  14. Turn ignition on, engine off. Using scan tool, command A/C relay on. If A/C relay clicks, go to step 23). If A/C relay does not click, go to next step.
  15. Disconnect A/C relay. Using a test light connected to ground, probe A/C relay cavity No. 86 (Pink wire), then cavity No. 87 (Orange wire). If test light comes on for both wires, go to step 17). If test light does not come on for both wires, go to next step.
  16. Repair open or short to ground in affected circuit. Go to step 27).
  17. Connect a test light between A/C relay cavity No. 86 (Pink wire) and cavity No. 85 (Dark Green/White wire). Using scan tool, command A/C relay on. If test light comes on, go to next step. If test light does not come on, go to step 19).
  18. Replace A/C relay. Go to step 27).
  19. Check A/C relay control circuit (Dark Green/White wire) for faulty connection at VCM harness connector. If a problem is found, go to next step. If no problem is found, go to step 21).
  20. Repair faulty connection at VCM. Go to step 27).
  21. Check for open in Dark Green/White wire between VCM and A/C relay. If a problem is found, go to next step. If no problem is found, go to step 26).
  22. Repair open in Dark Green/White wire. Go to step 27).
  23. Remove A/C relay. Using a fused jumper wire, jumper A/C relay cavity No. 87 (Orange wire) and cavity No. 30 (Dark Green wire) together. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, go to step 25).
  24. Replace A/C relay. Go to step 27).
  25. Repair open or short to ground in A/C compressor clutch control circuit (Dark Green wire). Go to step 27).
  26. Replace VCM. Go to next step.
  27. Using scan tool, select DTC CLEAR INFO. Start engine and allow it to reach normal operating temperature. Select DTC SPECIFIC, then enter DTC number that was set. Operate vehicle within conditions that may have set this DTC. If DTC does not reset, go to next step. If DTC resets, go to step 2).
  28. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any DTCs are displayed that have not been diagnosed, perform diagnosis for applicable DTC. See the TESTS W/CODES article. If no DTCs are displayed, system is okay.
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