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Climate Control System Operation



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CLIMATE CONTROL SYSTEM OPERATION - HYBRID

Description and Operation

The system components are the following:

- A/C compressor
- A/C compressor clutch assembly
- A/C condenser core
- A/C evaporator core
- Receiver/drier
- Connecting refrigerant lines
- Thermostatic expansion valve (TXV)
- Low charge protection switch
- Dual-function pressure switch
- Heater core and evaporator core housing
- Dual automatic temperature control (DATC) module
- Temperature blend door actuators
- Floor/defrost/panel door actuator
- Air inlet door actuator
- Blower motor resistor or speed control module
- Blower motor
- Ambient temperature sensor
- In-vehicle temperature sensor
- Solar radiation sensor
- Evaporator discharge air temperature sensor

Hybrid Climate Control System Components

The hybrid system consists of the following unique components:

- Auxiliary evaporator core
- Auxiliary thermal expansion valve (TXV)
- Underbody refrigerant lines
- Front evaporator thermistor
- Auxiliary evaporator thermistor
- Passenger zone valve
- Battery zone valve
- Traction battery control module (TBCM)
- DATC module
- PCM

The hybrid refrigerant system operation is controlled by the following:

Hybrid Climate Control System Operation

The PCM uses input from the TBCM, the DATC 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 opens the passenger zone valve and starts 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 disengages the A/C compressor clutch until the upper temperature threshold is reached within the front evaporator housing, at which time normal A/C operation begins 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 continues 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 resumes 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 causes 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, see - Auxiliary Climate Control.

A/C Compressor Operation


NOTE: The following A/C compressor operation description outlines A/C compressor operation based on control by the HVAC module only. The Traction Battery Control Module (TBCM) may override the HVAC module and independently operate the A/C compressor at any time if needed for High Voltage Traction Battery (HVTB) cooling.
The HVAC module will control A/C compressor operation based on the system settings. See the appropriate heading below for a description of operation in each climate control mode.

Defrost/Floor

- The HVAC module will transmit an A/C request to the PCM via the Instrument Cluster (IC).
- The A/C compressor will cycle per normal compressor operation if the ambient temperature is above freezing.
- The engine will run continuously and will not shut off when the A/C compressor cycles off if the ambient temperature is above freezing.
- The A/C compressor will not operate and the engine will cycle per normal hybrid operation if the ambient temperature is below freezing.

Defrost

- The HVAC module will transmit an A/C request to the PCM via the IC.
- The A/C compressor will cycle per normal compressor operation if the ambient temperature is above freezing.
- The engine will run continuously and will not shut off when the A/C compressor cycles off if the ambient temperature is above freezing.
- The A/C compressor will not operate and the engine will cycle per normal hybrid operation if the ambient temperature is below freezing.

Panel

- The HVAC module will transmit an A/C request to the PCM via the IC only if the A/C button is selected.
- If the ambient temperature is above approximately 10°C (50°F), the A/C button is selected and the ECON button is not selected, the engine will run continuously and the A/C compressor will cycle per normal A/C compressor operation.
- If the ambient temperature is below approximately 10°C (50°F), the A/C button is selected and the ECON button is not selected, the engine will cycle per normal hybrid operation and the A/C compressor will run only while the engine is running.
- If the A/C button is selected and the ECON button is selected, the engine will cycle per normal hybrid operation and the A/C compressor will run only while the engine is running.

Panel/Floor

- The HVAC module will transmit an A/C request to the PCM via the IC only if the A/C button is selected.
- If the ambient temperature is above approximately 10°C (50°F), the A/C button is selected and the ECON button is not selected, the engine will run continuously and the A/C compressor will cycle per normal A/C compressor operation.
- If the ambient temperature is below approximately 10°C (50°F), the A/C button is selected and the ECON button is not selected, the engine will cycle per normal hybrid operation and the A/C compressor will run only while the engine is running.
- If the A/C button is selected and the ECON button is selected, the engine will cycle per normal hybrid operation and the A/C compressor will run only while the engine is running.

Floor

- The HVAC module will transmit an A/C request to the PCM via the IC only if the A/C button is selected.
- If the ambient temperature is above approximately 10°C (50°F), the A/C button is selected and the ECON button is not selected, the engine will run continuously and the A/C compressor will cycle per normal A/C compressor operation.
- If the ambient temperature is below approximately 10°C (50°F), the A/C button is selected and the ECON button is not selected, the engine will cycle per normal hybrid operation and the A/C compressor will run only while the engine is running.
- If the A/C button is selected and the ECON button is selected, the engine will cycle per normal hybrid operation and the A/C compressor will run only while the engine is running.

Auto - Econ Mode Off

- The A/C button will be automatically selected and the indicator will be illuminated. The A/C button may be deselected to disable A/C operation.
- The HVAC module will transmit an A/C request and engine run request to the PCM via the IC if the HVAC module has determined that A/C operation is required to achieve the selected temperature.
- If the ambient temperature is below approximately 10°C (50°F), or if the HVAC module determines that A/C operation is not required to achieve the selected temperature, an A/C request and engine run request will not be sent; although, the A/C indicator will remain illuminated. The engine will cycle only per normal hybrid operation and the A/C compressor will not cycle.
- If the ambient temperature is above approximately 10°C (50°F), and A/C operation is required to achieve the set temperature, the engine will run continuously, and will not shut off when the A/C compressor cycles off. The A/C compressor will cycle per normal A/C compressor operation.

Auto - Econ Mode On


NOTE: For vehicles built after 3/2008, in high ambient temperatures, the A/C will engage and the engine will run continuously for a short initial cool down period to allow the A/C compressor to run. This is done to allow the passenger compartment to cool somewhat before the A/C compressor begins cycling off with the engine.

- The A/C button will be automatically selected, and the indicator will be illuminated. The A/C button may be deselected to disable A/C operation and the initial cool down period.
- The HVAC module will transmit an A/C request to the PCM via the IC.
- The HVAC module will sporadically send the engine run request.
- After the initial cool down period, the engine will not typically engage for the purpose of running the A/C compressor; therefore, the A/C compressor will run only when the engine is engaged per normal hybrid operation.

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