Noises generated by the air conditioning compressor (Mitsubishi Carisma)

First, it is necessary to determine the causes of the noise. These include: weather conditions, vehicle speed, which gear is engaged or in neutral, engine temperature, or other specific conditions. Noises that occur when the air conditioner is running can often be misleading. For example, noise similar to the sound of a faulty front bearing or a connecting rod knock can be caused by loose bolts, nuts, brackets, or loose (increased wear) of the air conditioner compressor clutch. Also check the tension of the alternator and power steering pump drive belts.

Incorrectly adjusted tension of the accessory drive belts when the air conditioner compressor clutch is engaged may cause noise that may be confused with the air conditioner compressor, and when the air conditioner compressor clutch is disengaged, little or no noise may be produced. The noise from the drive belts depends on their rotation speed. Therefore, depending on the belt tension at different engine speeds, the drive belts may produce extraneous noises that are often mistaken for the sounds of a faulty compressor.

Adjustment

1. Select a quiet location to conduct the test. Identify the conditions that produce the extraneous noise as closely as possible. Switch the compressor on and off several times to clearly isolate the sound of the compressor. Limit the air flow through the condenser to simulate high-altitude conditions. Install a measuring manifold assembly to monitor the discharge pressure, which should not exceed 2070 kPa.



2. Tighten all compressor mounting bolts, the air conditioner compressor clutch mounting bolt and adjust the compressor drive belt tension. Check the reliability of the electromagnetic clutch winding installation (no rotation or wobble).

3. Check that the air conditioning hoses do not touch or rub against adjacent parts, which may cause extraneous noise.

4. Check the refrigerant level.

5. Listen again to the sound of the compressor running.

6. If the noise remains, loosen the compressor mounting bolts and retighten them.

7. If the extraneous noise remains, replace the compressor and repeat the check.