Auxiliary Climate Control

HIGH-VOLTAGE TRACTION BATTERY COOLING SYSTEM

The high-voltage traction battery (HVTB) cooling system consists of the following components:
- Traction battery control module (TBCM)
- Auxiliary climate control housing
- Auxiliary evaporator discharge air temperature sensor
- Battery zone valve
- Thermostatic expansion valve (TXV)
- Auxiliary evaporator core
- Auxiliary evaporator outlet and inlet lines
- Battery zone air filter
- Auxiliary airflow mode door actuator

Auxiliary Climate Control Housing:

Fresh Air Mode Airflow Diagram:

Recirculated Mode Airflow Diagram:

Fresh Air Intake and Outlet Locations:

Traction Battery Control Module (TBCM)
The TBCM controls the battery temperature by activating or deactivating the fans contained within the HVTB, and by sending an A/C request signal to the PCM, if required. The TBCM also monitors the auxiliary evaporator discharge air temperature sensor and sends a signal to the PCM for A/C compressor and battery zone valve operation.

The TBCM is an integral part of the HVTB.

Auxiliary Evaporator Discharge Air Temperature Sensor
The auxiliary evaporator discharge air temperature sensor contains a thermistor which communicates the auxiliary evaporator air discharge temperature to the TBCM. The TBCM then sends a signal to the PCM to indicate if the auxiliary discharge air temperature signal is indicating a freeze or no-freeze condition.

When the A/C is operating for HVTB cooling, but has not been requested for the passenger compartment, the PCM prevents icing of the auxiliary evaporator core. It does this by switching off the A/C compressor when the TBCM indicates the auxiliary evaporator discharge air temperature sensor reading has fallen below acceptable levels, and by switching on the A/C compressor when the auxiliary evaporator temperature rises above acceptable levels.

When the A/C is operating for both the passenger compartment and HVTB cooling, the A/C compressor will continue to run (A/C request will remain ON), and the battery zone valve will be closed by the PCM if the auxiliary evaporator discharge air temperature sensor is reading a temperature below acceptable levels. This allows continued refrigerant flow to the front (main) evaporator core, while allowing the auxiliary evaporator core to warm to acceptable levels.

The evaporator discharge air temperature sensor is located on the auxiliary climate control housing.

Battery Zone Valve
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. 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.

Passenger Zone Valve
The passenger zone valve is a solenoid-type valve used by the PCM 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 requested for the passenger compartment. Refer to Heating and Air Conditioning for information on the passenger zone valve.

Auxiliary Evaporator Core
The evaporator core is an aluminum plate/fin-type and is located in the auxiliary climate control housing. A mixture of liquid refrigerant and oil enters the evaporator core through the auxiliary evaporator core inlet tube and continues out of the auxiliary evaporator core through the outlet tube as vapor. During A/C compressor operation, airflow through the auxiliary evaporator core housing is cooled and dehumidified as it flows through the evaporator core fins.

Thermostatic Expansion Valve (TXV)

NOTE: This vehicle is not equipped with an in-line TXV filter in the TXV inlet line.

The TXV is located at the evaporator core inlet and outlet tubes at the top of the auxiliary climate control housing. 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.

Auxiliary Airflow Mode Door Actuator
The TBCM uses an electric auxiliary airflow mode door actuator to position the 2 airflow mode doors in the auxiliary climate control housing. When A/C operation is not required for HVTB cooling, the TBCM will position the airflow mode doors to allow fresh air inlet and outlet. When A/C operation is required for HVTB cooling, the TBCM will position the airflow mode doors to the recirculated air position. When the airflow mode doors are in the recirculated air position, airflow from the HVTB will be cooled and dehumidified as it flows through the evaporator core and then returns to the HVTB.

The auxiliary airflow mode door actuator is located on the auxiliary climate control housing.

Battery Zone Air Filter

Battery Zone Air Filter:

The auxiliary evaporator core housing contains an auxiliary battery zone air filter. This is to reduce the amount of airborne particulates entering the battery compartment. An access panel is located on the RH quarter trim panel for the battery zone air filter. The air filter is located behind the battery zone air filter cover in the auxiliary evaporator core housing.

Refer to Maintenance/Service and Repair for battery zone air filter maintenance intervals.