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Air Conditioning System Overview



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AIR CONDITIONING SYSTEM OVERVIEW - HYBRID

Air Conditioning

- Electric A/C compressor
- A/C condenser core
- A/C evaporator core
- Receiver/drier
- Connecting refrigerant lines
- Thermostatic Expansion Valve (TXV)The refrigerant system incorporates an A/C compressor controlled by the PCM through an A/C clutch relay. The HVAC module sends an A/C request signal to the Instrument Cluster (IC), which relays the request to the PCM. An evaporator discharge air temperature sensor is used to cycle the A/C compressor off when the evaporator core temperature falls below an acceptable temperature.The HVAC module will send an A/C request signal to the IC if the ambient temperature is above approximately 35°F (2°C) and any one of the following conditions are met:

- A mode which requires A/C operation has been manually selected by the driver.
- The driver selects the A/C button while operating in manual mode.
- A/C is operating automatically via AUTO mode and the driver has not deselected A/C operation.

NOTE:The HVAC module will send the A/C request to the PCM as well as relaying the evaporator discharge air temperature sensor reading to the PCM. The PCM will then cycle the A/C compressor ON or OFF based on the sensor reading.
When an A/C request is received by the PCM, the A/C compressor will only be engaged through the A/C clutch relay if all of the following conditions are met:

- The evaporator discharge air temperature sensor is reading an acceptable temperature.
- The low-charge protection switch is not open due to excessively low refrigerant pressure.
- The A/C pressure transducer is reading an acceptable pressure in the high-pressure side of the refrigerant system.
- The engine coolant temperature is not excessively high.
- The PCM has not detected a Wide Open Throttle (WOT) condition.An A/C pressure relief valve is installed to protect the refrigerant system against excessively high refrigerant pressures.Refrigerant flow into the evaporator core is metered by a TXV.

Electric A/C Compressor

CAUTION:Electric Compressor Oil only must be used as a refrigerant system lubricant for hybrid vehicles. Addition of any oil other than Electric Compressor Oil to the hybrid vehicle electric refrigerant system will damage the electric Air Conditioning (A/C) compressor and contaminate the refrigerant system. See Refrigerant Oil Adding.
Hybrid vehicles are equipped with a variable-speed electric A/C compressor that is powered by the high-voltage traction battery system. The electric A/C compressor allows for A/C operation to continue even when the vehicle is in full electric mode and the gasoline engine is not running. The Air Conditioning Control Module (ACCM) is an integral part of the electric A/C compressor and cannot be removed from the compressor.

A/C Condenser

The A/C condenser is an aluminum fin-and-micro-channel design heat exchanger located in front of the vehicle radiator. It cools compressed refrigerant gas by allowing air to pass over fins and tubes to extract heat and by condensing gas to liquid refrigerant as it is cooled.

Evaporator Core

The evaporator core is an aluminum plate/fin-type and is located in the heater core and evaporator core housing. A mixture of liquid refrigerant and oil enters the bottom of the evaporator core through the evaporator core inlet tube and continues out of the evaporator core through the evaporator core outlet tube as a vapor. During A/C compressor operation, airflow from the blower motor is cooled and dehumidified as it flows through the evaporator core fins.

Thermostatic Expansion Valve (TXV)

The TXV is located at the evaporator core inlet and outlet tubes at the dash panel at the rear of the engine compartment. 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.

Receiver/Drier

NOTE:Installation of a new receiver/drier is not required when repairing the A/C system, except when there is physical evidence of contamination from a failed A/C compressor or damage to the receiver/drier. Damage to the receiver/drier includes leaks, physical damage to the receiver/drier shell or desiccant, or moisture contamination. Moisture contamination results only from a complete loss of refrigerant, and equalization of the refrigerant system pressure with atmospheric pressure for a period longer than one hour. If even a slight amount of positive refrigerant pressure is present in the refrigerant system before repairs are carried out, a new receiver/drier should not be installed.
The receiver/drier is mounted at the RH shock tower for hybrid vehicles. It stores high-pressure liquid after it leaves the condenser core. A desiccant cartridge mounted inside the receiver/drier removes any retained moisture from the refrigerant.

Evaporator Discharge Air Temperature Sensor

The evaporator discharge air temperature sensor contains a thermistor. The resistance of this thermistor varies by a specific amount based on the evaporator discharge air temperature. The HVAC module measures a voltage ratio between the reference voltage it supplies to the sensor and the sensor return voltage to determine this resistance and the associated discharge air temperature.The evaporator discharge air temperature sensor maintains evaporator core temperature and prevents icing of the evaporator core. It does this by signaling the PCM to cycle the A/C compressor off when the evaporator discharge air temperature sensor reading falls below acceptable levels. The A/C compressor will be switched back on when the evaporator temperature rises above acceptable levels.The evaporator discharge air temperature sensor is located on the heater core and evaporator core housing behind the glove compartment.

Dual-Function Pressure Switch

The dual-function pressure switch is located on the receiver/drier and includes 2 separate sets of contacts that are opened at 2 different pressures.The first set of contacts in the dual-function pressure switch is used to interrupt A/C compressor operation in the event of excessively high discharge pressure in the high-pressure side of the refrigerant system. The PCM monitors the first set of contacts in the dual-function pressure switch in-series with the low-charge protection switch. When the contacts are open, the PCM will disengage the A/C compressor.The second set of contacts in the dual-function pressure switch is used by the PCM to engage the high-speed cooling fan. When the A/C pressure rises above a preset level, the second set of contacts will close and the high-speed cooling fan will be engaged.The dual-function pressure switch is installed on a Schrader-type valve core fitting on the receiver/drier. It is not necessary to recover the refrigerant to remove the dual-function pressure switch.

Low-Charge Protection Switch

The low-charge protection switch is installed on the evaporator outlet line to cycle the A/C compressor off in the event of a low refrigerant charge. The PCM monitors the low-charge protection switch in-series with the dual-function pressure switch. When the low-side pressure drops below acceptable levels, the low-charge protection switch contacts open. When the low-charge protection switch contacts are open, the PCM will disengage the A/C compressor.The low-charge protection switch is installed on a Schrader-type valve core fitting on the evaporator outlet line. It is not necessary to recover the refrigerant to remove the low-charge protection switch.

Service Gauge Port Valves

The high-pressure service gauge port valve is located on the receiver/drier inlet line.The low-pressure service gauge port valve is located on the evaporator outlet line.
NOTE:Different valve cores are used for different engine applications Use only the valve core listed in the parts catalog for the vehicle and fitting being serviced.










The fitting is an integral part of the refrigerant line or component.

- Special couplings are required for both the high-side and low-side service gauge ports.
- A very small amount of leakage will always be detectable around the Schrader-type valve with the service gauge port valve cap removed, and is considered normal. A new Schrader-type valve core can be installed if the seal leaks excessively.
- The service gauge port valve caps are used as primary seals in the refrigerant system to prevent leakage through the Schrader-type valves from reaching the atmosphere. Always install and tighten the A/C service gauge port valve caps to the correct torque after they are removed.

Refrigerant System Dye

CAUTION:Fluorescent refrigerant system dye mixed with PAG oil should never be added to hybrid vehicle Air Conditioning (A/C) systems equipped with an electric Air Conditioning (A/C) compressor. Addition if fluorescent refrigerant system dye containing PAG oil will damage the electric A/C compressor and contaminate the refrigerant system.
For hybrid vehicles equipped with an electric compressor, additional refrigerant system dye should only be added by installing a new receiver/drier. Replacement receiver/driers include a fluorescent dye "wafer" which will dissolve after approximately one hour of continued A/C operation. Fluorescent refrigerant system dye mixed with PAG oil should never be used in hybrid vehicles with an electric A/C compressor.

Refrigerant Line Fittings

CAUTION:Use only a plastic or nonmetallic tool for removing O-ring seals and gasket seals from the refrigerant line fittings. Use of a metallic tool will create scratches on the sealing surface of the fitting that can result in refrigerant system leaks.
Whenever a refrigerant line fitting is disconnected, the fitting must be cleaned of any foreign material and new O-ring seals and/or gasket seals must be installed. Use only the O-ring seals and gasket seals specified in the parts catalog or equivalent.If a refrigerant system line fitting must remain disconnected for an extended period of time, it should be capped to avoid contamination of the refrigerant system.

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