Hybrid Climate Control System Operation

The PCM uses input from the TBCM, the EATC module and the front evaporator thermistor to determine the position of the passenger zone valve and the operation of the A/C compressor.

If cabin A/C is requested and the TBCM does not require cooling, the PCM sends a high speed controller area network (HS-CAN) message to the TBCM commanding the battery zone valve closed. The PCM will open the passenger zone valve and start the engine in order to run the A/C compressor if the ECON mode is not selected. The A/C system then operates similar to a standard vehicle, unless the PCM receives a signal from the front evaporator thermistor indicating an impending freezing condition. At that time, the PCM will disengage the A/C compressor clutch until the upper temperature threshold is reached within the front evaporator housing, at which time normal A/C operation will begin again.

If high-voltage battery cooling is active and cabin A/C is activated, the PCM opens the passenger zone valve and runs the engine continuously in order to operate the A/C compressor. The A/C system then operates similar to a standard vehicle, unless the PCM receives a signal from the front evaporator thermistor or the battery compartment thermistor indicating an impending freezing condition. When the front evaporator begins to freeze, the PCM will close the passenger zone valve until the temperature reaches the upper threshold. During this time, the A/C compressor will continue to run as long as the TBCM requests cooling and the battery compartment thermistor does not indicate an impending freezing condition. Normal cabin A/C operation will resume once the front evaporator reaches the upper temperature threshold.

When the cabin A/C is off, it is normal for the A/C compressor to run when high-voltage battery cooling is necessary. During this time, the passenger zone valve is closed and the gasoline engine may operate on demand or continuously based on these conditions to cool the battery.

If ECON mode is selected on the climate control assembly, the engine will not run continuously. It will turn off periodically, which will cause the vent discharge air temperature to rise until the engine turns on again.

For a complete description and operation of the battery zone valve and the passenger zone valve, refer to AUXILIARY CLIMATE CONTROL - HYBRID article.