A/C System Noise Check

Air conditioning refrigerant or lubricant vapor can irritate your eyes, nose, or throat.

Be careful when connecting service equipment.

Do not breathe refrigerant or vapor.

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

NOTE:

If an accidental system discharge occurs, ventilate the work area before resuming service.

Additional health and safety information may be obtained from the refrigerant and lubricant manufacturers.

Identify the conditions when the noise occurs. The weather, the vehicle speed, the vehicle being in gear or in neutral, the engine temperature, or other conditions may be factors in determining the noise source.

Do the A/C system inspection, and correct any problems found prior to diagnosing abnormal noises.

Abnormal A/C noises can be misleading. For example, a sound similar to a failed bearing may be caused by loose fasteners or a faulty A/C compressor clutch assembly.

1.	Other System - Noise Check

Turn the vehicle to the OFF (LOCK) mode, and check the following. Correct any problems found.

Drive belt

Excessive wear

Oil contamination

Improper belt routing

Faulty belt tensioner

Air inlet grille (in the cowl cover) for debris

Start the engine, run the A/C system, and check if the noise is coming from the following. Repair or replace any faulty components.

Drive belt

Belt tensioner

Any of the pulleys

2.	A/C System (Cabin) - Noise Check

Cycle the HVAC system through all blower speeds and all air distribution modes, and check for unusual noises and excessive vibration. If noise and/or vibration are present, do the following checks.

NOTE: During this inspection, close the doors and windows, and do not start the engine.

Check for

Result

Also Check for

Conditions when the noise occurs

The noise or vibration occurs only in a specific mode or setting.

Check the operation of the air mix control motor, door, and linkage.

Check the operation of the mode control motor, door, and linkage.

Check the operation of the recirculation control motor, door, and linkage.

There is a squeaking or chirping noise, but no unusual vibration.

Replace the blower motor.

Foreign material in the blower motor and fan

Foreign material (leaves or twigs, for example) is present.

Remove it, and recheck for noise.

No foreign material (leaves or twigs, for example) is present.

Remove the blower motor, and check these items below. Replace the blower motor if any problems are present.

Damage on the fan blades

Tightness of the fan retainer

Fan alignment on the blower motor shaft

3.	A/C System (Under-Hood) - Noise Check

Set up the vehicle for the running A/C checks:

Select a quiet area for testing.

Apply the parking brake.

Shift the vehicle to P, N position/mode, or Neutral.

Start the engine.

Set the A/C system to the following conditions:

Temperature control: MAX COOL

Mode control: VENT

Fan control: minimum (but not OFF)

A/C: ON

Switch the A/C 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.

Listen for noises coming from the A/C lines, the A/C hoses, the A/C condenser, the evaporator, the receiver/dryer, or the expansion valve, and check these items:

Check for	Result	Also Check for
Noises caused by A/C components touching other components or the body	The noise is present	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	Loose, damaged or excessively worn item is present	Repair or replace the faulty component(s) or hardware, and recheck for noise.
A moaning noise coming from the suction pipe and suction hose	A moaning noise is present	Check the system refrigerant charge. If the refrigerant charge is OK, replace the receiver/dryer.
A whistling or hissing noise from the expansion valve	A whistling or hissing noise is present	Evacuate the system for 3 hours, then recheck. If the noise is still present, replace the expansion valve.

Check the operation of the A/C compressor clutch:

Check for

Result

Also Check for

The A/C compressor clutch engages without slipping when the A/C is switched on.

Does slip

Replace the A/C compressor clutch.

Replace the A/C compressor also if there is a leak from the shaft seal.

Does not engage

Troubleshoot the A/C compressor clutch circuit.

The A/C compressor clutch disengages when the A/C is switched off.

Does not disengage

Do the A/C compressor clutch check. If the A/C compressor clutch is OK, replace the A/C compressor.

The A/C compressor clutch cycles on/off normally.

Rapid on/off cycle

Do the refrigerant leak check.

If the refrigerant charge is OK, and there are no leaks, troubleshoot the A/C compressor clutch circuit.

Listen with a stethoscope for noises coming from the A/C compressor, and check these items:

Check for	Result	Also Check for
The noise changes when the A/C compressor clutch disengages (off).	Does not change	Check for the noise coming from the engine-related components.
The A/C system operating pressures are normal.	Abnormal	Troubleshoot the problem using the pressure test table in the A/C system test. Correct the pressure-related problem(s), and recheck for noise.
The A/C compressor hose connections and fasteners are in good condition.	Loose, damaged, or excessively worn.	Repair or replace the faulty component(s) or hardware, and recheck for noise.
	In good condition	Replace the A/C compressor.