Changing the air conditioning compressor - troubleshooting & instructions

Check all retaining clamps and fixing points for breaks or cracks and any missing nuts or bolts.

Any vibration resulting from this may be the cause of excessive compressor noise. Observe whether the noise changes if you apply force onto the retaining clamps or fixing points using an assembly lever, for example (Figure 1). If the noise changes, the noises are most likely not being caused by the compressor.

Check the hoses and lines to determine whether vibrations from the engine or pulsing refrigerant are being transmitted to the vehicle interior.

For this purpose, hold them with one hand and observe possible changes in the noise (Figure 2).

Excessive high pressure (Figure 3) can cause unusual compressor noises.
 

If the high pressure service connection is located behind a blockage in the system, the high pressure may be higher than that indicated on the manometer. In order to diagnose such a problem, it is useful to measure the temperatures at the condenser.

The condenser can also be considered a cause of unusual noise.
 

If insufficient air is routed through the condenser, the refrigerant cannot sufficiently condense and the high pressure increases excessively. This can result in unusual noises. Therefore, check whether the fan(s) transport(s) sufficient air through the condenser. Check the condenser and radiator fins for possible contamination as well (Figure 4).

Noise can often also be caused by contaminated expansion valves (Figure 5) or throttle valves.
 

This can be caused by contamination in the form of metal abrasion, for example. This reduces the refrigerant flow and causes excessive high pressure. "Defective" expansion valves can generate various buzzing, whistling, or droning noises, for example, which are clearly audible in the vehicle interior.

Follow the manufacturer’s instructions and instruction leaflets/note the viscosity.

1. Distribution of the oil
There is refrigerant oil in every component of the air-conditioning system. The oil is removed with the replaced component during repairs. It is therefore essential to refill the appropriate quantity of oil. The graphic on the right shows the average distribution of the quantities of oil within the system.

2. Observe the quantity and specification of the oil
Before mounting a new compressor or when refilling refrigerant oil, always check the oil quantity and the viscosity in the vehicle manufacturer’s instructions.

3. Correct quantity of system oil in the compressor
As one and the same compressor can potentially be used for different vehicles or systems, it is essential that the oil filling quantity be checked/corrected before mounting the compressor. For this purpose, all the oil must be siphoned off and collected. The compressor must then be refilled with the entire oil quantity specified by the vehicle manufacturer (system oil quantity). To ensure that the oil is distributed equally, the compressor must be turned 10 times by hand before installation. This also corresponds to
the instructions from the compressor manufacturer Sanden;
specifications from the vehicle manufacturer
must be observed separately in each case.