Compressor HVAC: Testing and Inspection

COMPRESSOR NOISE DIAGNOSIS
Excessive noise while the air conditioning compressor is operating can be caused by loose compressor mounts, a loose compressor clutch, or high operating pressures in the refrigerant system. Verify compressor drive belt condition, proper compressor mounting, correct refrigerant charge level, and compressor head pressure before compressor repair is performed.

With the close tolerances within the compressor, it is possible to experience a temporary lockup. The longer the compressor is inactive, the more likely the condition is to occur. This condition is the result of normal refrigerant migration within the refrigerant system caused by ambient temperature changes. The refrigerant migration may wash the refrigerant oil out of the compressor.

NOTE: Prior to a vehicle being removed from service or stored for more than two weeks, the compressor should be operated to ensure adequate refrigerant oil distribution throughout the system components. Turn ON the air conditioner for a minimum of 5 minutes with outside air and the highest blower speed selected.

Belt Noise
If the compressor drive belt slips at initial start-up, it does not necessarily mean the compressor has failed. The following procedure can be used to identify a compressor drive belt noise problem.
- Start the vehicle and run at idle.
- Turn the air conditioner ON and listen for belt squeal.
- If belt squeal is heard, turn the air conditioner OFF immediately.

If the belt squeal stops when the air conditioner is turned OFF perform the following repair procedures.
1. Using an appropriate sized oil filter wrench or a strap wrench, grasp the outer diameter of the compressor clutch hub. While facing the compressor, rotate the hub clockwise, then counterclockwise. If the hub rotates, proceed to the next step. If the hub will not rotate, the compressor is internally damaged, and must be replaced.
2. Turn the hub clockwise five complete revolutions and remove the tool.
3. Start the vehicle and run at idle.
4. Turn the air conditioner ON. Observe the compressor and the system for normal operation, noting cooling performance and noise levels. Operate for 5 minutes before turning the air conditioner OFF. If acceptable cooling performance is observed during compressor operation, the compressor does not need to be replaced.
5. Inspect the drive belt for wear, damage, and proper tension.