Air Conditioning: Notes

WARNING: This page is about a different car, the 2011 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.

The A/C system components include the following:

A/C compressor
A/C clutch assembly
A/C condenser/transmission oil combo cooler
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 over the Medium Speed Controller Area Network (MS-CAN) to the Instrument Cluster (IC) which relays the request to the PCM over the High Speed Controller Area Network (HS-CAN). An evaporator discharge air temperature sensor is used to disengage the A/C compressor clutch when the evaporator core temperature falls below 5.5°C (42°F).

NOTE: To prevent erroneous readings that can result from underhood heat sources, the PCM uses data from several sources to calculate ambient temperature. The vehicle must be driven for a sufficient time, speed and distance after startup before the calculated ambient temperature is updated in the PCM. If a vehicle is moved from a below-freezing environment to a warm environment (such as being moved from outside into a garage, or when delivered from a cold climate to a warm climate), the minimal amount of driving may not be sufficient for the calculated ambient temperature to be updated. In this event, the PCM will believe the ambient temperature is too low for A/C operation and will not engage the A/C compressor in any mode to prevent an increased risk of compressor slugging or damage. To manually reset the PCM calculated ambient temperature to the current temperature, run the vehicle until the thermostat opens and then clear the PCM Keep Alive Memory (KAM). For the KAM resetting procedure, refer to ENGINE CONTROLS - INTRODUCTION - GASOLINE MODELS . When the PCM KAM is reset, the ambient temperature will reset to the current higher value (a value closer to actual surrounding conditions) and the A/C compressor will operate normally.

An A/C pressure relief valve is installed in the bottom rear of 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.