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HOMESERVICE MANUALSBUICK1996ROADMASTER BASEREPAIR AND DIAGNOSIS (SINGLE PAGE)HEATING, VENTILATION & A/C (HVAC)A/C COMPRESSOR CLUTCH CONTROLSTROUBLE SHOOTING CHARTSA/C CLUTCH CIRCUIT DIAGNOSISCOMPRESSOR CLUTCH CONTROL CIRCUIT DIAGNOSIS
1996 Buick Roadmaster Base

Compressor Clutch Control Circuit Diagnosis

1996 Buick Roadmaster BaseSECTION Compressor Clutch Control Circuit Diagnosis
  1. If On-Board Diagnostic (OBD) System Check has not been performed, see appropriate ENGINE PERFORMANCE article in the ENGINE PERFORMANCE section and go to OBD SYSTEM CHECK. If OBD SYSTEM CHECK has been performed, go to next step.
  2. Check if any Diagnostic Trouble Codes (DTCs) are stored. If any DTCs are set, perform diagnosis for codes first. See appropriate ENGINE PERFORMANCE article in the ENGINE PERFORMANCE section and go to OBD SYSTEM CHECK. If no DTCs are set, go to next step.
  3. Install scan tester. Run engine at idle. Turn A/C off. Using scan tester on ENG 1 data list, monitor A/C REQUEST. If scan tester indicates A/C REQUEST as YES, go to step 9). If scan tester does not indicate A/C REQUEST as YES, go to next step.
  4. Turn ignition on. Turn A/C on. If scan tester indicates A/C REQUEST as YES, system is now operating correctly. If scan tester does not indicate A/C REQUEST as YES, go to next step.
  5. Disconnect A/C pressure cycling switch. Using test light, probe A/C pressure cycling switch harness connector (Dark Green wire). If test light comes on, go to next step. If test light does not come on, see article below:
  6. Using a fused jumper wire, jumper terminals "A" (Dark Blue wire) and "B" (Dark Green/White wire) together at A/C pressure cycling switch harness connector. If scan tester indicates A/C REQUEST as YES, go to step 13). If scan tester does not indicate A/C REQUEST as YES, go to next step.
  7. Turn ignition off. Disconnect PCM connector C2. Check continuity of A/C request circuit (Dark Green/White wire) between PCM and A/C pressure cycling switch. If A/C request circuit is open, go to step 15). If A/C request circuit is not open, go to next step.
  8. Check continuity of A/C request circuit to ground. If A/C request circuit is shorted to ground, go to step 16). If A/C request circuit is not shorted to ground, go to step 12).
  9. Disconnect A/C pressure cycling switch. If scan tester indicates A/C REQUEST as YES, go to next step. If scan tester does not indicate A/C REQUEST as YES, see appropriate article below:
  10. Using a test light connected to ground, probe A/C request circuit at A/C pressure cycling switch harness connector (Dark Green/White wire). If test light comes on, go to next step. If test light does not come on, go to step 17).
  11. Repair A/C request circuit for a short to voltage.
  12. Check PCM connections. If connections are okay, go to step 17). If a connection repair was made, system should now be okay.
  13. Check A/C pressure cycling switch harness connector connections. If connections are okay, go to step 14). If a connection repair was made, system should now be okay.
  14. Replace A/C pressure cycling switch.
  15. Repair open A/C request circuit (Dark Green/White wire) between switch and PCM.
  16. Repair grounded A/C request circuit (Dark Green/White wire) between switch and PCM.
  17. Replace PCM.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.