Air Conditioning

AIR CONDITIONING

The auxiliary evaporator housing contains an auxiliary battery zone air filter. This is to reduce the amount of airborne particulates entering the battery compartment. The filter is located inside the auxiliary evaporator housing.

The battery zone air filter should be:
- Inspected every 10,000 miles (16,000 km) and replaced if needed.
- Replaced every 20,000 miles (32,000 km).

To remove the air filter, remove the LH rear quarter trim access panel. The air filter is located behind the auxiliary evaporator housing access door.

The A/C refrigerant system is a clutch cycling orifice-type tube including a thermostatic expansion valve 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 thermostatic expansion valve (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 evaporative 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 traction battery control module (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 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.

A/C Compressor and Clutch Assembly

NOTE:
- Internal A/C compressor components are not repaired separately. Install a new A/C compressor only as an assembly. The A/C clutch disc and hub assembly, A/C clutch pulley and A/C clutch field coil are repairable.
- Installation of a new suction accumulator is not required when repairing the air conditioning system except when there is physical evidence of system contamination from a failed A/C compressor or damage to the suction accumulator.

The SC90V variable scroll A/C compressor has the following characteristics:
- Variable capacity function controlled by a suction pressure sensing device
- Fixed and orbiting scroll to provide refrigerant compression
- Non-repairable shaft seal
- A/C compressor uses PAG compressor oil (oil contains special additives necessary for the A/C compressor)
- A/C compressor contains a thermal cut-out switch which senses the A/C compressor housing temperature (switch disengages the A/C compressor clutch if the housing temperature exceeds 120°C (247°F).

The magnetic A/C clutch has the following characteristics:
- Drives the compressor shaft
- When battery positive voltage (B+) is applied to the A/C clutch field coil, the clutch disc and hub assembly is drawn toward the A/C clutch pulley
- 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 B+ is removed from the A/C clutch field coil, springs in the clutch disc and hub assembly move the clutch disc away from the A/C clutch pulley

A/C Compressor Pressure Relief Valve
An A/C compressor pressure relief valve is incorporated in the compressor A/C manifold and tube to:
- relieve unusually high refrigerant system discharge pressure buildups of 3,792 kPa (550 psi) and above.
- prevent damage to the A/C compressor and other system components.
- avoid total refrigerant loss by closing after the excessive pressure has been relieved.

Refrigerant Lines

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

The condenser to evaporator line contains high-pressure liquid refrigerant upstream of the evaporator core orifice. The A/C manifold and tube assembly is attached to the compressor with O-ring seals.

There is also an additional set of lines that carry refrigerant to the rear evaporator for high-voltage battery cooling. These lines are spliced into the front lines in the engine compartment and the liquid line contains a filter.

Evaporator Core

NOTE: Installation of a new suction accumulator is not required when repairing the air conditioning system except when there is physical evidence of system contamination from a failed A/C component or damage to the suction accumulator.

There are 2 evaporator cores on the vehicle: one in the front evaporator housing and one in the auxiliary evaporator housing. The evaporator core is the plate/fin type.

The front evaporator core is for cabin cooling and the rear evaporator core is for high-voltage battery cooling.

Front Evaporator Core Orifice Tube

NOTE:
- Install a new evaporator core orifice whenever a new A/C compressor is installed.
- Adjustment or repair cannot be made to the evaporator core orifice. A new evaporator core orifice must be installed.

The front evaporator core orifice has the following characteristics:
- Color-coded orange
- Orifice diameter of 1.44 mm (0.057 inch)
- Located in the condenser-to-evaporator line
- Changes the high-pressure liquid refrigerant into a low-pressure liquid
- Filter screens located on the inlet and outlet ends of the orifice body
- the inlet filter screen acts as a strainer for the liquid refrigerant flowing through the A/C evaporator core orifice
- O-ring seals on the evaporator core orifice prevent the high-pressure liquid refrigerant from bypassing the evaporator core orifice

Air Conditioning (A/C) Low Charge Protection Switch
The A/C low charge protection switch is mounted on a Schrader-type valve fitting on the top of the suction accumulator.
- A valve depressor, located inside the threaded end of the A/C low charge protection switch presses in on the Schrader-type valve stem.
- This allows the suction pressure inside the suction accumulator to control the operation of the A/C low charge protection switch.
- The electrical switch contacts open when the suction pressure drops to 80-90 kPa (11-13 psi).
- The contacts close when the suction pressure rises to 276 max kPa (40 psi max).
- While the A/C low charge protection switch is closed, voltage is sent to the PCM signaling normal pressure in the A/C system, and the PCM continues to control operation of the A/C compressor based on other inputs.
- When the A/C low charge protection switch contacts open, voltage is removed to the PCM and the A/C compressor is disengaged.
- It is not necessary to discharge the refrigerant system to remove the A/C low charge protection switch.

High Pressure Cutoff Switch
The high pressure cutoff switch, also referred to as the dual function pressure switch, is used to interrupt A/C compressor operation and/or the electric engine cooling fan in the event of high system discharge pressures.
- The high pressure cutoff switch is mounted on a Schrader-type valve fitting on the high pressure side of the condenser to evaporator line.
- A valve depressor, located inside the threaded end of the dual function pressure switch, is used to monitor the compressor discharge pressure.
- It is not necessary to discharge the refrigerant system to remove the dual function pressure switch.
- The high pressure cutoff switch has 2 sets of contacts. One electrical contact is normally closed.
- When the compressor discharge pressure rises to approximately 3,000-3,275 kPa (435-475 psi), the switch contacts open, signaling the PCM to disengage the A/C compressor.
- When the pressure drops to approximately 1,517-1,931 kPa (220-280 psi), the contacts close to allow operation of the A/C compressor.

The switch contains a second set of electrical contacts used for high-speed fan control.
- When the compressor discharge pressure reaches approximately 2,137-2,344 kPa (310-340 psi), these contacts close and send a signal to the PCM to engage the high-speed fan control.
- When the pressure drops to approximately 1,655-2,137 kPa (240-310 psi), the contacts again open and the high speed fan control is disengaged.