A/C System Noise Testing

A/C SYSTEM NOISE

CAUTION: The A/C condenser and receiver/drier must be replaced as an assembly if an internal failure of the A/C compressor has occurred. Failure to replace the A/C condenser and receiver/drier can cause serious damage to the replacement A/C compressor A/C Condenser - Removal .

When investigating an A/C system related noise, you must first know the conditions under which the noise occurs. These conditions include: weather, vehicle speed, transmission in gear or neutral, engine speed, engine temperature, and any other special conditions. Noises that develop during A/C operation can often be misleading. For example: What sounds like a failed front engine bearing or connecting rod, may be caused by loose bolts, nuts, mounting brackets or a loose compressor clutch assembly.

Drive belts are speed sensitive. At different engine speeds and depending upon drive belt tension, drive belts can develop noises that are mistaken for an A/C compressor noise. Improper drive belt tension can cause a misleading noise when the compressor clutch is engaged, which may not occur when the compressor clutch is disengaged. Check the accessory drive belt condition and tension as described in Cooling before beginning this procedure.

1. Select a quiet area for testing. Duplicate the complaint conditions as much as possible. Turn the A/C compressor On and Off several times to clearly identify the compressor noise.
2. Loosen all of the compressor mounting hardware and retighten. Check the A/C clutch. Be certain that the clutch coil, clutch plate and pulley are mounted securely to the A/C compressor, and that the clutch plate and pulley are properly aligned and have the correct air gap.
3. To duplicate high-ambient temperature conditions (high head pressure), restrict the air flow through the A/C condenser. Install a manifold gauge set or a scan tool to be certain that the high side pressure does not exceed 3.53 MPa (512 psi).
4. Check the refrigerant system plumbing for incorrect routing, rubbing or interference, which can cause unusual noises. Also check the refrigerant lines and hoses for kinks or sharp bends that will restrict refrigerant flow, which can cause noises.
5. Listen to the A/C compressor while the clutch is engaged and disengaged. Probe the A/C compressor with an engine stethoscope or a long screwdriver with the handle held to your ear to better localize the source of the noise. If the noise is from the A/C compressor, conduct the A/C Performance test and verify refrigerant charge level A/C Performance.
6. If the A/C clutch and refrigerant charge level is ok, but the noise persists, replace the A/C compressor A/C Compressor - Removal.