Compressor HVAC: Testing and Inspection

Excessive noise while using the A/C system, can be caused by loose mounts, loose clutch, or high operating pressure. Verify compressor drive belt condition, proper refrigerant charge and head pressure before compressor repair is performed.

With the close tolerances of a compressor, it is possible to experience a temporary lockup. The longer the A/C system is inactive, the more likely the condition is to occur.

This condition is the result of normal refrigerant movement within the A/C system caused by temperature changes. The refrigerant movement may wash the oil out of the compressor.

NOTE: Anytime a vehicle is to be out of service or stored for more than two weeks, the A/C system should be operated to insure adequate oil flow throughout the system components. Turn on the A/C system for a minimum of 5 minutes using the Fresh Air and High Blower mode.

If the A/C drive belt slips at initial start-up, it does not necessarily mean the compressor has failed.

The following steps can be used to diagnose noise problems.
- Start the vehicle and run at idle.
- Turn the A/C system ON and listen for drive belt squeal.
- Immediately turn the system OFF if squealing is heard.
- If squealing stops when the A/C is turned OFF, perform the following procedures.

1. Using an appropriate sized oil filter removal tool or strap wrench, grasp the outer diameter of the A/C compressor clutch hub that houses the rubber doughnut. 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 can be replaced following the Compressor Replacement directions.
2. Turn the hub clockwise 5 complete revolutions and remove the tool.
3. Start the vehicle, engage the A/C system and run at idle.
4. Observe the A/C compressor and system for normal operation, noting A/C performance and noise levels. Operate for 5 minutes before shutdown. If acceptable performance continues during operation, the compressor does not need to be replaced.