Fixed Displacement A/C Compressor

NOTE: Proper Air Conditioning (A/C) system diagnosis on a vehicle's compressor is dependent on correct refrigerant system charge and tested in ambient temperatures above 21.1 °C (70 °F).

The fixed displacement compressor has:

a non-serviceable shaft seal.
a serviceable pressure relief valve installed in the rear of the compressor to protect the refrigerant system against excessively high refrigerant pressures.
a serviceable A/C clutch and field coil.
Fixed displacement A/C compressors use Motorcraft ® PAG Refrigerant Compressor Oil (YN-12-D). This oil contains special additives required for the A/C compressor. The oil may have some slightly dark-colored streaks while maintaining normal oil viscosity. This is normal for this A/C compressor because of break-in wear that can discolor the oil.

Fixed displacement A/C compressors are always at 100% displacement. The pistons are placed around an angled plate (swash plate) and are pushed back and forth as the plate rotates. Cooling performance is controlled by switching the compressor clutch on or off depending upon the evaporator temperature.