Air Conditioning

AIR CONDITIONING

The A/C refrigerant system is a clutch cycling orifice-type tube including a thermostatic expansion valve (TXV) type auxiliary system for traction battery cooling. The system consists of the following components:
- A/C compressor
- A/C clutch
- A/C condenser core
- A/C evaporator core
- A/C compressor pressure relief valve
- Auxiliary evaporator core
- Auxiliary TXV
- Underbody refrigerant lines
- In-line TXV filter inside the auxiliary evaporator inlet line at the TXV inlet connection
- A/C charge port valve (high side)
- A/C charge port valve (low side)
- Connecting refrigerant lines
- Suction accumulator

The refrigerant system operation is controlled by the following:
- Front evaporator thermistor
- Auxiliary evaporator thermistor
- Passenger zone valve
- Battery zone valve
- Traction battery control module (TBCM)
- Function selector switch
- A/C evaporator core orifice
- A/C cycling (low charge protection) switch
- High pressure cutoff switch
- Powertrain control module (PCM)
- Dual function pressure switch (DFPS)

The refrigerant system incorporates an A/C compressor controlled by the PCM.

In addition, the A/C low charge protection switch senses A/C evaporator core pressure to protect the A/C compressor due to a low refrigerant charge.

The dual function pressure switch (DFPS) is used to interrupt the A/C compressor operation in the event of high system discharge pressures. The DFPS is mounted on a Schrader-type valve fitting on the compressor manifold and tube assembly. It is not necessary to recover the refrigerant when removing the switch. A valve depressor, located in the threaded end of the DFPS, presses on the Schrader-type valve stem allowing the DFPS to monitor the A/C compressor discharge pressure. When the compressor discharge pressure rises, the switch contacts open allowing the PCM to disable the A/C compressor operation. When the compressor discharge pressure drops, the switch contacts close, allowing the PCM to enable the A/C compressor operation.

The DFPS has a second set of electrical contacts used for high-speed cooling fan control. When the A/C compressor discharge pressure rises, the contacts close and send a signal to the PCM requesting high-speed cooling fan operation. When the pressure drops, the contacts open and the signal for high speed engine cooling fan operation is removed.

An A/C evaporator core orifice is installed in the condenser to evaporator line to meter the liquid and vapor refrigerant mixture into the A/C evaporator core.

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

If cabin MAX A/C is selected 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. 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 MAX 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.

If the A/C or A/C RECIRC position 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.