Air Conditioning: Notes

WARNING: This page is about a different car, the 2010 Ford Focus. However, it is still accessible from the selected car via links, so may be relevant.

The refrigerant system components include the following:

A/C compressor and clutch assembly
A/C condenser core
A/C evaporator core
Receiver/drier
Connecting refrigerant lines
Thermostatic Expansion Valve (TXV)

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 to the Instrument Cluster (IC), which relays the request to the PCM. An evaporator discharge air temperature sensor is used to cycle the A/C compressor off when the evaporator core temperature falls below an acceptable temperature.

The HVAC module will send an A/C request signal to the instrument cluster if the following conditions are met:

A mode which requires A/C operation has been manually selected by the driver.
The A/C evaporator discharge air temperature sensor is reading an acceptable temperature.

When an A/C request is received, the A/C compressor clutch will only be engaged by the PCM through the A/C clutch relay if all of the following conditions are met:

The A/C pressure transducer is reading an acceptable pressure in the high-pressure side of the refrigerant system.
The engine coolant temperature is not excessively high.
The PCM has not detected a Wide Open Throttle (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.