Externally Controlled Variable Displacement A/C Compressor

WARNING: This page is about a different car, the 2020 Lincoln Nautilus. However, it is still accessible from the selected car via links, so may be relevant.

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 externally controlled variable displacement compressor has:

a non-serviceable shaft seal.
a non-serviceable pressure relief valve installed in the rear of the compressor to protect the refrigerant system against excessively high refrigerant pressures.
Refer to Specifications for the appropriate refrigerant and refrigerant oil. 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.

Variable displacement compressors have a swash plate that rotates to reciprocate pistons, which compresses refrigerant. Variable displacement compressors change the swash plate angle to change the refrigerant displacement. The externally controlled variable displacement compressor changes the swash plate angle in response to an electrical signal from the PCM. The externally controlled variable displacement compressor manages displacement by controlling refrigerant differential pressure before and after a throttle at the discharge side; achieving precise cooling capability control in response to cabin environment and driving conditions.

The PCM sends a PWM signal to the solenoid in the compressor to control the compressor displacement based upon the:

Ambient air temperature
Evaporator temperature
Engine RPM
Vehicle speed
A/C high side pressure
Temperature and mode settings of the climate control head
Intake air temperature