Tech Tips

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Air Conditioning

Automotive Air Conditioning - Glossary of Terms

ACCUMULATOR: A liquid vapor separator that stores and dries the refrigerant. It is located in the low pressure side between the evaporator and the compressor. Used on late model GM, Fords and Imports with the fixed orifice tube.

BLOWER FAN: A motor-driven fan used to force air through the evaporator or heater core and circulate air through the passenger compartment.

CLUTCH CYCLING SWITCH: A switch which uses evaporator core temperature or pressure to control electrical current to the compressor clutch field coil to prevent the evaporator core from freezing.

COMPRESSOR: Refrigeration pump that circulates refrigerant and increases the pressure of refrigerant vapor.

COMPRESSOR CLUTCH: An electro-magnetic coupling that connects or disconnects the belt driven compressor pulley to the compressor shaft.

CONDENSER: System component that removes heat from the refrigerant, changing it from a hot vapor to a warm liquid. It is usually located in the front of the vehicle's radiator.

CYCLING CLUTCH ORIFICE TUBE (CCOT): Designation for a system used by GM, Ford and some Imports that utilizes an accumulator and orifice tube instead of a receiver-drier and expansion valve. The system operates by using a thermostatic switch or a pressure sensing switch to cycle compressor operation.

CYCLING CLUTCH SYSTEM: A system which controls evaporator temperature by turning the compressor on and off with a clutch cycling switch.

DESICCANT: A drying agent used in refrigeration systems to remove excess moisture (molecular sieve or similar substance).

DISCHARGE LINE: Connects the compressor outlet to the condenser inlet.
EVAPORATOR: System component that removes heat from the air entering the passenger compartment. The refrigerant enters as a low pressure liquid, and leaves as a low pressure vapor. It is located near the vehicle cowl.

EXPANSION VALVE: See "THERMOSTATIC EXPANSION VALVE"

HIGH PRESSURE CUT OFF SWITCH: Found mainly on FWD vehicles, this switch will disengage the compressor clutch when excessive discharge pressure is sensed.

LIQUID LINE: Refrigerant line connecting the condenser outlet to the evaporator inlet.

LOW PRESSURE CUT-OUT SWITCH: Located either in the high pressure or low pressure side of the system, it disengages the compressor clutch when system pressure drops below a predetermined valve.

RECEIVER-DRIER: A canister that contains a desiccant to remove moisture and is used to store and filter liquid refrigerant. The receiver-drier is located in the liquid line between the condenser outlet and expansion valve inlet.

SIGHT GLASS: A window in the liquid line or in top of drier used to observe the liquid refrigerant flow.

SUCTION LINE: The line connecting evaporator outlet to compressor inlet.

SUCTION THROTTLING VALVES (STV & POA VALVES): Used on some systems to control refrigerant flow to prevent evaporator freeze-up.

THERMOSTATIC EXPANSION VALVE: A component regulating rate of refrigerant flow into evaporator as governed by evaporator outlet pipe temperatures sensed by the sensing bulb.

VARIABLE DISPLACEMENT COMPRESSOR: A design of compressor that changes its output based on vehicle heat load, rather than cycling the compressor clutch off and on.

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