Air Conditioning: Notes

WARNING: This page is about a different car, the 2008 Mercury Milan, 2008 Lincoln MKZ, and 2008 Ford Fusion. 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
A/C clutch assembly
A/C condenser core
A/C evaporator core
Receiver/drier cartridge
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 climate control assembly sends an A/C request signal to the instrument cluster module, which relays the request to the PCM. An evaporator discharge air temperature sensor is used to disengage the A/C compressor clutch when the evaporator core temperature falls below an acceptable temperature.

The A/C compressor clutch will only be engaged by the PCM 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 Instrument Cluster (IC).
The evaporator discharge air temperature sensor is reading an acceptable temperature.
The A/C pressure transducer is reading an acceptable pressure in the high side of the refrigerant system.
The A/C compressor relay is switched to the closed position by the PCM.
The engine coolant temperature is not excessively high.
The PCM has not detected a Wide Open Throttle (WOT) condition.

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

Refrigerant flow into the evaporator core is metered by a TXV.