Air Conditioning

Air Conditioning


Air Conditioning System Overview

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 A/C 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 TXV and evaporator core located under the LH rear quarter panel.

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 (or close the passenger zone valve on hybrid vehicles) when the evaporator core temperature falls below an acceptable temperature.

Hybrid vehicles also use the A/C 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 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 operation in manual mode.
- A/C is operating automatically via AUTO mode and the driver has not deselected A/C operation.

NOTE: For 2.5L 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 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. For 2.5L 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.


A/C Compressor and Clutch Assembly

NOTE: Internal A/C compressor components are not serviced separately. The A/C compressor is serviced only as an assembly. The A/C compressor clutch, A/C compressor pulley and A/C clutch field coil are serviceable.

NOTE: Installation of a new receiver/drier is not required when repairing the A/C system, except when there is physical evidence of contamination from a failed A/C compressor or damage to the receiver/drier.

The A/C compressor has the following characteristics:

- A non-serviceable shaft seal.
- The A/C compressor uses PAG Refrigerant Compressor Oil (R-134a Systems) YN-12-D. This oil contains special additives required for the A/C compressor.
- The A/C compressor oil in the A/C system may darken over time while maintaining normal oil viscosity. This is normal for A/C systems because of break-in wear and the addition of fluorescent leak detection dye that can discolor the oil.
- Use the oil matching procedure specified for this vehicle when installing a new A/C compressor or any other A/C component.

When battery voltage is applied to the A/C compressor clutch field coil, the clutch disc and hub assembly is drawn toward the A/C clutch pulley. The magnetic force locks the clutch disc and hub assembly and the A/C clutch pulley together as one unit, causing the compressor shaft to rotate. When battery voltage is removed from the A/C compressor clutch field coil, springs in the clutch disc and hub assembly move the clutch plate away from the A/C clutch pulley.


Thermal Protection Switch (Hybrid Only)

Under high A/C load conditions, the A/C compressor temperature may get hot enough to trigger the compressor thermal protection switch which will disengage the A/C compressor clutch. The thermal protection switch is located in the A/C compressor housing, near the discharge port and is wired in series with the A/C clutch field coil. When refrigerant discharge temperatures heat the switch to 115°C (239°F), the switch will open and disengage the compressor, but no PCM DTCs will be set. The switch will close once the temperature cools to approximately 105°C (221°F). If the switch were to stick open, it would remain open at room temperature.


A/C Condenser

The A/C condenser is an aluminum fin-and-micro-channel design heat exchanger located in front of the vehicle radiator. It cools compressed refrigerant gas by allowing air to pass over fins and tubes to extract heat and by condensing gas to liquid refrigerant as it is cooled.

On 2.5L or 3.0L (4V) vehicles equipped with an automatic transmission, the top portion of the condenser is partitioned from the refrigerant system and is used for transmission fluid cooling.


Evaporator Core

NOTE: A second (auxiliary) evaporator core is used for HVTB cooling on hybrid vehicles.

The evaporator core is an aluminum plate/fin-type and is located in the heater core and evaporator core housing. A mixture of liquid refrigerant and oil enters the bottom of the evaporator core through the evaporator core inlet tube and continues out of the evaporator core through the evaporator core outlet tube as a vapor. During A/C compressor operation, airflow from the blower motor is cooled and dehumidified as it flows through the evaporator core fins.


Thermostatic Expansion Valve (TXV)

NOTE: A second (auxiliary) TXV is used for High Voltage Traction Battery (HVTB) cooling on hybrid vehicles.

The TXV is located at the evaporator core inlet and outlet tubes at the dash panel at the rear of the engine compartment. The TXV provides a restriction to the flow of refrigerant from the high-pressure side of the refrigerant system and separates the low-pressure and high-pressure sides of the refrigerant system. Refrigerant entering and exiting the evaporator core passes through the TXV through 2 separate flow paths. An internal temperature sensing bulb senses the temperature of the refrigerant flowing out of the evaporator core and adjusts an internal pin-type valve to meter the refrigerant flow into the evaporator core. The internal pin-type valve decreases the amount of refrigerant entering the evaporator core at lower temperatures and increases the amount of refrigerant entering the evaporator core at higher temperatures.


Receiver/Drier

NOTE: Installation of a new receiver/drier is not required when repairing the A/C system, except when there is physical evidence of contamination from a failed A/C compressor or damage to the receiver/drier. Damage to the receiver/drier includes leaks, physical damage to the receiver/drier shell or desiccant, or moisture contamination. Moisture contamination results only from a complete loss of refrigerant, and equalization of the refrigerant system pressure with atmospheric pressure for a period longer than one hour. If even a slight amount of positive refrigerant pressure is present in the refrigerant system before repairs are carried out, a new receiver/drier should not be installed.

The receiver/drier is mounted to the right of the radiator support for 2.5L or 3.0L (4V) vehicles, or at the RH shock tower for hybrid vehicles. It stores high-pressure liquid after it leaves the condenser core. A desiccant cartridge mounted inside the receiver/drier removes any retained moisture from the refrigerant.


Evaporator Discharge Air Temperature Sensor

NOTE: A second (auxiliary) evaporator discharge air temperature sensor is used for the auxiliary evaporator core on hybrid vehicles.

The evaporator discharge air temperature sensor contains a thermistor. The resistance of this thermistor varies by a specific amount based on the evaporator discharge air temperature. The HVAC module measures a voltage ratio between the reference voltage it supplies to the sensor and the sensor return voltage to determine this resistance and the associated discharge air temperature.

The evaporator discharge air temperature sensor maintains evaporator core temperature and prevents icing of the evaporator core. It does this by signaling the HVAC module to switch off the A/C request signal to the instrument cluster on 2.5L or 3.0L (4V) vehicles, or signaling the PCM to cycle the A/C compressor off when the evaporator discharge air temperature sensor reading falls below acceptable levels. The A/C request or A/C compressor will be switched back on when the evaporator temperature rises above acceptable levels.

On hybrid vehicles, the A/C compressor will continue to run and the passenger zone valve will be closed by the PCM if the evaporator discharge air temperature sensor is reading a temperature below acceptable levels, but the TBCM is requesting A/C operation for HVTB cooling. This allows continued refrigerant flow to the auxiliary evaporator core while allowing the front (main) evaporator core to warm to acceptable levels.

The evaporator discharge air temperature sensor is located on the heater core and evaporator core housing behind the glove compartment.


A/C Pressure Transducer (2.5L or 3.0L [4V] Only)

The A/C pressure transducer monitors the compressor discharge pressure and communicates with the PCM. The PCM will interrupt A/C compressor operation in the event that the A/C pressure transducer indicates high system discharge pressures. It is also used to sense low charge conditions. If the pressure is below a predetermined value for a given ambient temperature, the PCM will not allow the clutch to engage.

The A/C pressure transducer is located on the receiver/drier. It is not necessary to recover the refrigerant before removing the A/C pressure transducer.


Dual-Function Pressure Switch (Hybrid Only)










The dual-function pressure switch is located on the receiver/drier and includes 2 separate sets of contacts that are opened at 2 different pressures.

The first set of contacts in the dual-function pressure switch is used to interrupt A/C compressor operation in the event of excessively high discharge pressure in the high-pressure side of the refrigerant system. The PCM monitors the first set of contacts in the dual-function pressure switch in-series with the low-charge protection switch. When the contacts are open, the PCM will disengage the A/C compressor clutch.

The second set of contacts in the dual-function pressure switch is used by the PCM to engage the high-speed cooling fan. When the A/C pressure rises above a preset level, the second set of contacts will close and the high-speed cooling fan will be engaged.

The dual-function pressure switch is installed on a Schrader-type valve core fitting on the receiver/drier. It is not necessary to recover the refrigerant to remove the dual-function pressure switch.


Low-Charge Protection Switch (Hybrid Only)










The low-charge protection switch is installed on the evaporator outlet line to cycle the A/C compressor off in the event of a low refrigerant charge. The PCM monitors the low-charge protection switch in-series with the dual-function pressure switch. When the low-side pressure drops below acceptable levels, the low-charge protection switch contacts open. When the low-charge protection switch contacts are open, the PCM will disengage the A/C compressor clutch.

The low-charge protection switch is installed on a Schrader-type valve core fitting on the evaporator outlet line. It is not necessary to recover the refrigerant to remove the low-charge protection switch.


Passenger Zone Valve (Hybrid Only)

The passenger zone valve is a solenoid-type valve used on hybrid vehicles to isolate the front (main) evaporator core from the refrigerant system when the A/C compressor is operating for HVTB cooling and A/C operation has not been selected for the passenger compartment. When A/C operation has been selected for the passenger compartment, the passenger zone valve will also be closed to prevent freezing of the front evaporator core if the front evaporator discharge air temperature sensor indicates that the front evaporator temperature has fallen below acceptable levels, while the auxiliary evaporator discharge air temperature sensor is reading within acceptable levels. This is done to prevent the A/C compressor from having to be cycled off when HVTB cooling is still required.

When voltage is applied to the passenger zone valve, it will be in the open state. When voltage is removed, the passenger zone valve will be in the closed state.

The passenger zone valve will only be in either the fully open or the fully closed state and cannot be partially opened.

The passenger zone valve is mounted at the top of the RH shock tower.


Battery Zone Valve (Hybrid Only)

The battery zone valve is a solenoid-type valve used by the PCM on hybrid vehicles to isolate the auxiliary evaporator core from the refrigerant system, when the A/C compressor is operating for passenger compartment cooling and A/C operation has not been requested for HVTB cooling. When A/C operation is requested for HVTB cooling, the battery zone valve will also be closed to prevent freezing of the auxiliary evaporator core if the auxiliary evaporator discharge air temperature sensor indicates that the auxiliary evaporator temperature has fallen below acceptable levels, while the front (main) evaporator discharge air temperature sensor is reading within acceptable levels. This is done to prevent the A/C compressor from having to be cycled off when passenger compartment cooling is still required.

The battery zone valve will periodically be briefly opened during front (main) A/C operation for system maintenance. When A/C operation is not requested, the battery zone valve is closed.

When voltage is applied to the battery zone valve, it will be in the open state. When voltage is removed, the battery zone valve will be in the closed state. The battery zone valve will only be in the fully open or the fully closed state and cannot be partially opened.

The battery zone valve is mounted to the bottom of the auxiliary climate control housing.


Service Gauge Port Valves

The high-pressure service gauge port valve is located on the receiver/drier inlet line.

The low-pressure service gauge port valve is located on the evaporator outlet line.

NOTE: Different valve cores are used for different engine applications. Use only the valve core listed in the Ford Master Parts Catalog for the vehicle and fitting being serviced.










The fitting is an integral part of the refrigerant line or component.

- Special couplings are required for both the high-side and low-side service gauge ports.
- A very small amount of leakage will always be detectable around the Schrader-type valve with the service gauge port valve cap removed, and is considered normal. A new Schrader-type valve core can be installed if the seal leaks excessively.
- The service gauge port valve caps are used as primary seals in the refrigerant system to prevent leakage through the Schrader-type valves from reaching the atmosphere. Always install and tighten the A/C service gauge port valve caps to the correct torque after they are removed.


Refrigerant System Dye

Fluorescent refrigerant system dye is added to the refrigerant system at the factory to assist in refrigerant system leak diagnosis using a Rotunda-approved ultraviolet blacklight. It is not necessary to add additional dye to the refrigerant system before diagnosing leaks, even if a significant amount of refrigerant has been removed from the system. Replacement receiver/driers are shipped with a fluorescent dye "wafer" included in the desiccant cartridge, which will dissolve after approximately 30 minutes of continued A/C operation. It is not necessary to add dye after flushing or filtering the refrigerant system because a new receiver/drier is installed as part of the flushing or filtering procedure. Additional refrigerant system dye should only be added if more than 50 percent of the refrigerant system lubricant capacity has been lost due to a fitting separation or hose rupture.


Refrigerant Line Fittings

NOTICE: Use only a plastic or nonmetallic tool for removing O-ring seals and gasket seals from the refrigerant line fittings. Use of a metallic tool will create scratches on the sealing surface of the fitting that can result in refrigerant system leaks.

Whenever a refrigerant line fitting is disconnected, the fitting must be cleaned of any foreign material and new O-ring seals and/or gasket seals must be installed. Use only the O-ring seals and gasket seals specified in the Ford Master Parts Catalog.

If a refrigerant system line fitting must remain disconnected for an extended period of time, it should be capped to avoid contamination of the refrigerant system.