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A/C System Noise Diagnosis

WARNING: This page is about a different car, the 2002 GMC Safari and 2002 Chevrolet Astro. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Definition: Noise originating from the A/C compressor, drive belt, or the A/C lines.
  1. Were you sent here from SYMPTOM DIAGNOSIS  or another diagnostic table? If so, go to next step. If not, see TROUBLE SHOOTING .
  2. A/C system noises can be generally categorized into 3 areas:
    • Screeching, squealing or chirping noises.
    • Moaning noises.
    • Vibration/rattle noises.
    Start the engine. Ensure that the A/C is on. Is a screeching, squealing noise heard when the A/C is engaged? If so, go to next step. If not, go to step  9.
  3. With the engine off, inspect the drive belt for excessive wear. Is the drive belt excessively worn? If so, go to step  18. If not, go to next step.
  4. Inspect the drive belt tension. See BELT ADJUSTMENT in COOLING SYSTEM SPECIFICATIONS & DRIVE BELT ROUTING - ALL MODELS article in ENGINES. Is the drive belt tension correct? If so, go to next step. If not, go to step  19.
  5. Inspect the drive belt for excess oil coverage. Is the drive belt covered with oil? If so, go to step  17. If not, go to next step.
  6. Start the engine. Ensure that the A/C is on. Inspect the compressor and the clutch. Is the compressor locked up? If so, go to step  24. If not, go to next step.
  7. Is the A/C compressor clutch slipping? If so, go to step  23. If not, go to next step.
  8. Using a stethoscope, listen to the A/C compressor for any abnormal noises. Is the compressor causing an abnormal noise? If so, go to step  15. If not, go to step  10.
  9. Does a moaning noise exist when the A/C clutch is engaged? If so, go to next step. If not, go to step  12.
  10. Listen to the A/C compressor components and mounting for noise concerns using a stethoscope. Are any of these components loose, damaged or excessively worn? If so, go to step  20. If not, go to next step.
  11. Idle the engine. Engage the A/C compressor clutch. Using a stethoscope, move around the entire refrigerant plumbing system, inspecting for any abnormal noises caused by component ground-out. Are any of the A/C components grounding out and causing a noise? If so, go to step  22. If not, go to step  13.
  12. Does a vibration or rattle noise exist when the A/C clutch is engaged? If so, go to next step. If not, go to step  14.
  13. Does the noise stop when the A/C clutch is disengaged? If so, go to step  15. If not, go to step  25.
  14. Idle the engine in Park with the A/C compressor clutch engaged. Using a stethoscope, move around the entire A/C system testing for any abnormal noises caused by a component. Do any of the A/C components cause an abnormal noise? If so, go to step  21. If not, go to step  25.
  15. Verify that the A/C system is properly charged. See SPECIFICATIONS  and PERFORMANCE TESTS  . Is the A/C system properly charged? If so, go to step  26. If not, go to next step.
  16. Recharge the A/C system to specification. See RECOVERY, EVACUATION & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Is the abnormal compressor noise still present? If so, go to step  24. If not, go to step  26.
  17. Repair the oil leak. See appropriate ENGINE MECHANICAL article in ENGINES. After repairs are complete, go to step  26.
  18. Replace the drive belt. See appropriate ENGINE MECHANICAL article in ENGINES. After repairs are complete, go to step  26.
  19. Replace the drive belt tensioner. See appropriate ENGINE MECHANICAL article in ENGINES. After repairs are complete, go to step  26.
  20. Repair or replace the A/C compressor mounting component. After repairs are complete, go to step  26.
  21. Repair or replace the component which is causing the moaning concern as needed. After repairs are complete, go to step  26.
  22. Correctly route or insulate the A/C component. After repairs are complete, go to step  26.
  23. After repairs are complete, go to step  26.
  24. Replace the A/C compressor clutch. See COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs are complete, go to step  26.
  25. The concern may be caused by an engine related component. See appropriate ENGINES article. After repairs, go to next step.
  26. Operate the system in order to verify the repair. If system operates normally, repair is complete. If system still malfunctions, return to step  2.
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