Air Conditioning System Overview

WARNING: This page is about a different car, the 2008 Mercury Mariner and 2008 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:

A/C compressor and clutch assembly
A/C condenser core
A/C evaporator core
Receiver/drier
Connecting refrigerant lines
Thermostatic expansion valve (TXV)
Passenger zone valve (hybrid only)
Battery zone valve (hybrid only)
Auxiliary evaporator core (hybrid only)
Auxiliary TXV (hybrid only)

NOTE: An auxiliary air conditioning system is used only on hybrid vehicles for high-voltage traction battery (HVTB) cooling. The auxiliary system branches off of the main refrigerant system circuit to an additional thermostatic expansion valve (TXV) and evaporator core located under the LH rear quarter panel. For information on hybrid-specific auxiliary system components, refer to AUXILIARY CLIMATE CONTROL - HYBRID article.

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, which relays the request to the PCM. An evaporator discharge air temperature sensor is used to cycle the A/C compressor off (or close the passenger zone valve on hybrid vehicles) when the evaporator core temperature falls below an acceptable temperature.

Hybrid vehicles also use the air conditioning system for HVTB cooling. The traction battery control module (TBCM) will also send an A/C request to the PCM if HVTB cooling is required.

The HVAC module will send an A/C request signal to the instrument cluster 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 operation in manual mode.
A/C is operating automatically via AUTO mode and the driver has not deselected A/C operation.

NOTE: For 2.3L or 3.0L (4V) 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 clutch will only be engaged through the A/C clutch relay if all of the following conditions are met:

The low-charge protection switch is not open due to excessively low refrigerant pressure.
The dual-function pressure switch is not open due to excessively high refrigerant pressure.
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. For 2.3L or 3.0L (4V) vehicles, the A/C pressure relief valve is located on the A/C compressor. For hybrid vehicles, the pressure relief valve is located on the A/C compressor manifold and tube assembly at the compressor manifold fitting.

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