LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> HVAC Systems - Manual >> Symptom Tests >> Test A: A/C Compressor Clutch Does Not Engage >> 4.3L Engine

4.3L Engine

NOTE: For circuit reference, see CONNECTOR IDENTIFICATION  and/or WIRING DIAGRAMS  .
  1. Perform DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After check is complete, go to next step.
  2. Install scan tool. Start engine. Using scan tool, observe ENGINE COOLANT TEMPERATURE (ECT) parameter in Powertrain Data List. If scan tool indicates ENGINE COOLANT TEMPERATURE parameter is greater than 275°F (125°C), check engine for overheating condition. Repair as necessary. If scan tool indicates ENGINE COOLANT TEMPERATURE parameter is less than 275°F (125°C), go to next step.
    3. NOTE: Ambient (outside) air temperature must be greater than 38°F (3°C).
  3. Start engine. Place blower motor switch in maximum speed position. Press A/C switch to ON position. Place air temperature switch in coldest position. If A/C compressor operates, problem is intermittent. Check wiring and connections. If A/C compressor does not operate, go to next step.
  4. Park vehicle out of direct sunlight. Open windows to ventilate interior of vehicle. Allow A/C system to equalize for approximately 2 minutes. Turn ignition off. Install manifold gauge set. Record ambient air temperature at vehicle. Record readings of low and high side STATIC pressures. Compare low and high side pressure values with allowable limits for the recorded ambient air temperature. See Figure. If low and high side pressure values are within allowable limits for recorded ambient air temperature, and within 15 psi (1.1 kg/cm2 ) of each other, go to next step. If low and high side pressure values are within allowable limits for recorded ambient air temperature, and/or are not within 15 psi (1.1 kg/cm2 ) of each other, leak test vehicle. See LEAK TESTING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING.
  5. If HVAC control assembly is inoperative, go to step  18. If HVAC control assembly is operative, go to next step.
  6. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter in Powertrain Engine Data 2 list. Place air temperature switch in coldest position. Place mode switch in bi-level position. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step  8. If scan tool indicates A/C REQUEST SIGNAL parameter is NO, go to next step.
  7. Turn ignition off. Disconnect A/C high pressure switch. Connect a 3-amp fused jumper wire between A/C request signal circuits at A/C high pressure switch connector. Start engine. Using scan tool, observe A/C REQUEST SIGNAL parameter. Place air temperature switch in coldest position. Place mode switch in bi-level position. If scan tool indicates A/C REQUEST SIGNAL parameter is YES, go to step  31. If scan tool indicates A/C REQUEST SIGNAL parameter is NO, go to step  24.
  8. If scan tool indicates A/C COMPRESSOR CYCLING SWITCH parameter is NORMAL, go to step  10. If scan tool does not indicate A/C COMPRESSOR CYCLING SWITCH parameter is NORMAL, go to next step.
  9. Turn ignition off. Disconnect A/C low pressure switch. Connect a 3-amp fused jumper wire between A/C low pressure switch signal and ground circuits. Start engine. Using scan tool, observe A/C COMPRESSOR CYCLING SWITCH parameter. If scan tool indicates A/C COMPRESSOR CYCLING SWITCH parameter is NORMAL, go to step  28. If scan tool does not indicate A/C COMPRESSOR CYCLING SWITCH parameter is NORMAL, go to step  20.
  10. Using scan tool, command A/C Relay ON and OFF. If A/C compressor clutch relay turns 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.
  11. Turn ignition off. Disconnect A/C compressor clutch relay. Turn ignition on. Probe coil side voltage supply circuit of A/C compressor clutch relay with test light connected to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step  26.
  12. Connect a test light between A/C compressor clutch relay control circuit and coil side voltage supply circuit. 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.
  13. If test light remains illuminated with each command, go to step  17. If test light does not remain illuminated with each command, go to step  16.
  14. Turn ignition off. Disconnect the A/C compressor clutch relay. Probe A/C compressor clutch relay switch side voltage supply circuit with test light connected to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step  25.
  15. Connect a 10-amp fused jumper wire between switch side voltage circuit of A/C compressor clutch relay and A/C compressor clutch supply voltage circuit of A/C compressor clutch. If A/C compressor clutch engages, go to step  27. If A/C compressor clutch does not engage, go to step  22.
  16. Check A/C compressor clutch relay control circuit for an open. Repair circuit as necessary, then go to step  39. If circuit is okay, go to step  32.
  17. Check A/C compressor clutch relay control circuit for a short to ground. Repair circuit as necessary, then go to step  39. If circuit is okay, go to step  32.
  18. Check HVAC control assembly ignition voltage circuit for a short to ground, a high resistance, or an open. Repair circuit as necessary, then go to step  39. If circuit is okay, go to next step.
  19. Check HVAC control assembly ground circuit for an open. Repair circuit as necessary, then go to step  39. If circuit is okay, go to step  30.
  20. Check A/C low pressure switch signal circuit for a high resistance or an open. Repair circuit as necessary, then go to step  39. If circuit is okay, go to next step.
  21. Check A/C low pressure switch ground circuit for a high resistance or an open. Repair circuit as necessary, then go to step  39. If circuit is okay, go to step  32.
  22. Check A/C compressor clutch supply voltage circuit at A/C compressor clutch for a short to ground, a high resistance, or an open. Repair circuit as necessary, then go to step  39. If circuit is okay, go to next step.
  23. Check A/C compressor clutch ground circuit for a high resistance or an open. Repair circuit as necessary, then go to step  39. If circuit is okay, go to step  29.
  24. Turn ignition off. Reconnect A/C high pressure switch. Check both A/C request signal circuits at high pressure switch for a short to ground, a high resistance, or an open. Repair circuit as necessary, then go to step  39. If circuit is okay, go to step  32.
  25. Repair A/C compressor clutch relay switch side voltage supply circuit. After repairs are complete, go to step  39.
  26. Repair A/C compressor clutch relay coil side voltage supply circuit. After repairs are complete, go to step  39.
  27. Check A/C compressor clutch relay for loose wires and/or poor connections. Repair as necessary, then go to step  39. If wiring and connections are okay, go to step  33.
  28. Check A/C low pressure switch for loose wires and/or poor connections. Repair as necessary, then go to step  39. If wiring and connections are okay, go to step  34.
  29. Check A/C compressor clutch harness connector for loose wires and/or poor connections. Repair as necessary, then go to step  39. If wiring and connections are okay, go to step  36.
  30. Check HVAC control module harness connector for loose wires and/or poor connections. Repair as necessary, then go to step  39. If wiring and connections are okay, go to step  37.
  31. Check A/C high pressure switch for loose wires and/or poor connections. Repair as necessary, then go to step  39. If wiring and connections are okay, go to step  35.
  32. Check PCM harness connector for loose wires and/or poor connections. Repair as necessary, then go to step  39. If wiring and connections are okay, go to step  38.
  33. Replace A/C compressor clutch relay. See COMPRESSOR RELAY  under REMOVAL & INSTALLATION. After replacement, go to step  39.
  34. Replace A/C low pressure switch. See PRESSURE SWITCHES  under REMOVAL & INSTALLATION. After replacement, go to step  39.
  35. Replace A/C high pressure switch. See PRESSURE SWITCHES  under REMOVAL & INSTALLATION. After replacement, go to step  39.
  36. Replace A/C compressor clutch coil. See COMPRESSOR SERVICING in GENERAL SERVICING. After replacement, go to step  39.
  37. Replace HVAC control assembly. See HVAC CONTROL ASSEMBLY  under REMOVAL & INSTALLATION. After replacement, go to step  39.
  38. Replace and reprogram PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - BLAZER (JIMMY CANADIAN), SONOMA & S10 PICKUP article in ENGINE PERFORMANCE. After replacement, go to next step.
  39. Operate system to verify repair. If system does not operate properly, go to step  4. If system operates correctly, test is complete.
scientia non olet · About LEMON Manuals