Compressor HVAC: Testing and Inspection

When investigating an air conditioning related noise, you must first know the conditions when the noise occurs. These conditions are: weather, vehicle speed, in gear or neutral, engine temperature, or any other special condition.

Noises that develop during air conditioning operation can often be misleading. For example: what sounds like a failed front bearing or connecting rod, may be caused by loose bolts, nuts, mounting brackets, or a loose clutch assembly Improper drive belt tension can cause a misleading noise when compressor is engaged. The noise may not occur when compressor is disengaged.

Drive belt(s) are speed sensitive. At different engine speeds and depending upon belt tension, belt(s) can develop noises that are mistaken for a compressor noise.

1. Select a quiet area for testing. Duplicate conditions as much as possible. Switch compressor on and off several times to clearly identify compressor noise. Listen to compressor clutch while engaged and disengaged.
2. To duplicate high-ambient condition (high-head pressure), restrict air flow through condenser. Install manifold gauge set to make sure discharge pressure doesn't exceed 2,070 kPa (300 psi).
3. Tighten ALL compressor mounting bolts, clutch mounting bolt, clutch coil mounting screws
4. Check refrigerant hoses for rubbing or interference which can cause unusual noises.
5. Check refrigerant charge (refer to Charging the System).
6. Check compressor noise as in Step 1.
7. If noise still exists, loosen compressor mounting bolts and torque. Repeat Step 1.
8. If noise continues, replace compressor and repeat Step 1.