Air Conditioning Component: AC Compressor - Houston's Premier Auto Repair Facility

​Most automotive air conditioning compressors use reciprocating piston compressors, consisting of a main shaft, wobble plate, pistons, valve plate and the compressor housing. In older designs, the angle of the wobble plate was fixed, which meant the pistons always moved the full length of the cylinder. Newer designs have variable wobble plates which allows the compressor load to be adjusted to match the demand for cooling.

The AC Compressor is driven by a belt attached to the engine. The belt always turns the AC pulley, but unless the compressor clutch is engaged by turning on the air conditioning in the car, the pulley will be disconnected from the compressor main shaft so that the internal parts of the compressor will not turn. When the clutch is engaged, the pistons inside the compressor suck the refrigerant out of the evaporator, and force it into the condenser. The pumping action of the compressor will increase the refrigerant pressure from around 30 psi to about 250 psi. Compressors can fail as a result of weak internal valves, worn seals on the pistons, failed clutches, or leaking external seals.

Moving parts inside the compressor can eventually wear, and as a result, small particles are introduced into the A/C system. These small particles increase the wear on the moving parts inside the compressor. As parts deteriorate, the compressor is less able to compress the refrigerant gas to the required pressure, and the air conditioning system is unable to sufficiently cool the vehicle. To resolve this problem, the compressor must be replaced and all particles must be flushed from the system. Failure to flush the system adequately can result in the new compressor being damaged and failing prematurely.

Air conditioning system components such as the expansion valve or metering device, receiver drier, and in some cases the condenser, can also accumulate small particles from the failed compressor that cannot be flushed out. These components must be replaced along with the compressor in order for the new compressor warranty to be valid.

Before replacing the compressor, the refrigerant gas is evacuated from the system, and the refrigerant oil separated from the gas. Most of the system is then dismantled so that the flush procedure can be performed. A solvent mixed with compressed air is sprayed through each part of the system, then each part is sprayed again using compressed air with no solvent. The system is reassembled and placed under vacuum before refilling the system with refrigerant gas and oil.

Services > Air Conditioning & Heating> Air Conditioning System Parts > AC Compressor

Function: Compresses and circulates refrigerant throughout the cooling system.

Signs of Wear: Lack of or insufficient cooling, excessive clicking sounds or unusual noises when using the A/C system.

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