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Test C: A/C System Noise

WARNING: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.
NOTE: For circuit reference, see CONNECTOR IDENTIFICATION  and/or WIRING DIAGRAMS  .
NOTE: Definition: Noise originating from the A/C compressor, drive belt or the A/C lines.
  1. Were you sent here from another test? If so, go to next step. If not, see SYMPTOM DIAGNOSIS  under TROUBLE SHOOTING. If problem is not found in SYMPTOM DIAGNOSIS, go to next step.
  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 in ENGINE COOLING. Is the drive belt tension correct? If so, go to next step. If not, go to step  19.
  5. Inspect the drive belt for excessive 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 A/C 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. Listening for any abnormal noises caused by a component of the A/C system touching another component. Are any of the A/C components grounding out and causing a vibration 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 Figure. 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, EVACUATING & 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 repair procedure in ENGINE MECHANICAL article in ENGINES. After repairs are complete, go to step  26.
  18. Replace the drive belt. After repairs are complete, go to step  26.
  19. Replace the drive belt tensioner. See TENSIONER under REMOVAL & INSTALLATION in 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. Replace the A/C compressor clutch. See COMPRESSOR SERVICING article in GENERAL SERVICING. After repairs are complete, go to step  26.
  24. Replace the A/C compressor. See COMPRESSOR  in REMOVAL & INSTALLATION. After repairs are complete, go to step  26.
  25. The concern may be caused by an engine related component. Repair component as necessary. After repairs are complete, go to step  26.
  26. Operate the system in order to verify the repair. Did you find and correct the condition? If so, system is okay. If not, go to step  2.
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