Air Conditioning System Overview

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

NOTE: All component descriptions contained in this system description are common for both non-hybrid and hybrid Escape/Mariner vehicles unless specified otherwise.

The refrigerant system components include the following:

Pulley driven A/C compressor and clutch assembly (non-hybrid)
Electric A/C compressor (hybrid)
A/C compressor clutch assembly (non-hybrid)
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 IC if the ambient temperature is above approximately 35°F (2°C) and any one of the following conditions are met:

A mode which requires A/C operation has been manually selected by the driver.
The driver selects the A/C button while operating in manual mode.
A/C is operating automatically via AUTO mode and the driver has not deselected A/C operation.

NOTE: For non-hybrid vehicles, the HVAC module will also require the evaporator discharge air temperature sensor to be reading an acceptable evaporator core temperature before sending an A/C request to the PCM. For hybrid vehicles, the HVAC module will send the A/C request to the PCM as well as relaying the evaporator discharge air temperature sensor reading to the PCM. The PCM will then cycle the A/C compressor ON or OFF based on the sensor reading.

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

The evaporator discharge air temperature sensor is reading an acceptable temperature.
The low-charge protection switch is not open due to excessively low refrigerant pressure.
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 pressure relief valve is installed to protect the refrigerant system against excessively high refrigerant pressures.

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