Air Conditioning: Notes

WARNING: This page is about a different car, the 2014 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

The A/C refrigerant system is a clutch cycling TXV type. The system components are the following:

A/C compressor
A/C condenser core
A/C evaporator core
Connecting refrigerant lines

The refrigeration system operation is controlled by the following:

TXV
Evaporator temperature sensor
A/C compressor pressure relief valve
A/C pressure transducer

The refrigerant system incorporates an A/C compressor controlled by the PCM through an A/C clutch relay. The HVAC module sends an A/C request signal over the MS-CAN to the BCM which relays the request over the HS-CAN to the PCM . An evaporator temperature sensor is used to disengage the A/C compressor clutch when the evaporator core temperature is slightly above the freezing point of water.

The PCM commands the A/C clutch relay to turn on the A/C compressor clutch if all of the following conditions are met:

The HVAC module is set to a mode which provides an A/C request to the PCM via the IPC .
The evaporator temperature sensor is reading an acceptable temperature.
The A/C pressure transducer is not reading a pressure above 2, 841 kPa (412 psi) in the high side of the refrigerant system.
The A/C pressure transducer is not reading a pressure that is too low (indicating a low charge condition) in the high-pressure side of the refrigerant system.
The engine coolant temperature is not excessively high.
The PCM has not detected a WOT condition.

An A/C compressor pressure relief valve is installed in the A/C compressor to protect the refrigerant system against excessively high refrigerant pressures as a redundant backup to the A/C pressure transducer.