A/C System Noise Check

The A/C system noise check will help you determine the source of abnormal A/C system noise

1. Inspect the air inlet grille in the cowl cover for debris If debris is present, remove it
2. Sit inside the vehicle, close the doors and windows, and turn the ignition switch to ON (II), but do not start the engine Cycle the HVAC system through all blower speeds and all air distribution modes to determine where and when the noise occurs
3. Operate the blower at each speed with the engine and A/C off, and check for unusual noises and excessive vibration If noise and/or vibration are present, do the following checks
   1. If the noise or vibration occurs only in a specific mode or setting, then check these items
      • Operation of the mode control motor, door, and linkage
      • Operation of the air mix control motor(s), door(s), and linkage
      • Operation of the recirculation motors, doors, and linkage
   2. -2 If there is a squeaking or chirping noise, but no unusual vibration, replace the blower motor (see BLOWER UNIT COMPONENT REPLACEMENT )
   3. -3 Remove the blower unit (see BLOWER UNIT REMOVAL/INSTALLATION ), and check for foreign material (leaves or twigs, for example) on the blower motor and fan If foreign material is present, remove it, and recheck for noise If you don't find any foreign material, remove the blower motor (see BLOWER UNIT COMPONENT REPLACEMENT ), and check these items
   • Check if the fan blades are cracked or broken
   • Make sure the fan retainer is tight
   • Inspect the fan alignment on the blower motor shaft

   Replace the blower motor if any problems are present

4. Set up the vehicle for the running A/C checks
   • Select a quiet area for testing
   • Apply the parking brake
   • Shift the vehicle in PARK or in Neutral
   • Start the engine
   • Set the temperature control button to Max Cool
   • Set the mode control button to Vent
   • Set the fan ON/OFF button to minimum (but not OFF)
   • Turn the A/C button ON

   Switch the compressor on and off several times to clearly identify the sound during A/C compressor operation Listen to the noise while the A/C compressor clutch is engaged and disengaged Probe the A/C system with a stethoscope to pinpoint the noise

   NOTE: If the noise does not change when the A/C compressor clutch engages or disengages, the noise may be caused by an engine-related component Probe the engine area with a stethoscope to pinpoint the noise
5. Turn the ignition switch to LOCK (0), and check the drive belt for excessive wear, oil contamination, improper routing, or a faulty belt tensioner (see DRIVE BELT INSPECTION ) Correct any problems found Start the engine, run the A/C system, and check if the noise is coming from the drive belt, the belt tensioner or any of the pulleys Repair or replace any faulty components
6. Listen for noises coming from the A/C lines, the A/C hoses, the condenser, the evaporator, the receiver-drier, or the expansion valve, and check these items
   • Noises caused by A/C components touching other components or the body Reroute or insulate the A/C component(s) as needed, and recheck for noise
   • Loose, damaged or excessively worn A/C components or mounting hardware Repair or replace the faulty component(s) or hardware, and recheck for noise
   • A moaning noise from the A/C suction line If there is a moaning noise, check the system refrigerant charge (see SYSTEM CHARGING ) If the refrigerant charge is OK, replace the receiver/dryer
   • A whistling or hissing noise from the expansion valve Evacuate the system for 3 hours (see SYSTEM EVACUATION ), then recheck If the noise is still present, replace the expansion valve (see EXPANSION VALVE REPLACEMENT )
7. Check the operation of the A/C compressor clutch
   • Make sure compressor clutch engages without slipping If the clutch does not engage, troubleshoot the A/C compressor clutch circuit (see A/C COMPRESSOR CLUTCH CIRCUIT TROUBLESHOOTING ) If the compressor clutch slips, replace the complete clutch assembly (see A/C COMPRESSOR CLUTCH OVERHAUL )
   • Make sure the A/C compressor clutch disengages If the clutch does not disengage, do the A/C compressor clutch circuit troubleshooting (see A/C COMPRESSOR CLUTCH CIRCUIT TROUBLESHOOTING ) If the clutch circuit is OK, do the A/C compressor clutch check (see A/C COMPRESSOR CLUTCH CHECK ), and see if the clutch is mechanically jammed If there are no electrical or mechanical problems with the compressor clutch, replace the A/C compressor (see A/C COMPRESSOR REPLACEMENT )
   • Make sure the A/C compressor clutch cycles normally If the compressor clutch is cycling rapidly, the A/C system is probably low on refrigerant due to a leak Do the refrigerant leak check (see REFRIGERANT LEAK CHECK ) If the refrigerant charge is OK, and there are no leaks, troubleshoot the A/C compressor clutch circuit
8. Listen with a stethoscope for noises coming from the A/C compressor, and check these items
   • The noise changes when the compressor clutch disengages If the noise does not change when the A/C compressor disengages, the noise may be caused by an engine-related component Probe the engine area with a stethoscope to pinpoint the noise
   • The A/C system operating pressures are normal If the system pressures are abnormal, troubleshoot the problem using the pressure test table in the A/C system test (see A/C SYSTEM TEST ) Correct the pressure-related problem(s), and recheck for noise
   • The A/C compressor hose connections, mounting brackets, and fasteners are in good condition If any of these components are loose, damaged, or excessively worn, repair or replace the faulty component(s), and recheck for noise If these components are in good condition, and the noise is still present, replace the A/C compressor (see A/C COMPRESSOR REPLACEMENT )