A/C Refrigerant System Operation

A/C REFRIGERANT SYSTEM OPERATION







Refrigerant Flow
During stabilized (A/C system shutdown) conditions, refrigerant system pressures are equalized on both the high and low sides of the refrigerant system. When an A/C, mix or defrost function is selected and the vehicle requires cooling, the system operates as follows:
^ The A/C clutch field coil is energized and the A/C clutch is pulled into contact with the belt-driven A/C clutch pulley.
^ The A/C clutch then rotates the compressor shaft.
^ When the A/C compressor shaft is rotated, the refrigerant vapors from the suction side of the refrigerant system are compressed into a decreasingly smaller area, increasing the refrigerant vapor pressure and also raising the refrigerant vapor temperature.
^ The high-pressure and high-temperature A/C compressor discharge refrigerant vapor is released into the A/C condenser core assembly through the A/C manifold and tube.
^ In the A/C condenser core, high pressure refrigerant vapor condenses into high pressure liquid when heat is removed from the refrigerant vapor by outside air passing over A/C condenser core fins and tubing.
^ High pressure liquid refrigerant from the bottom of the A/C condenser core enters the inlet side of the A/C evaporator core orifice.
^ Refrigerant pressure is reduced in the A/C evaporator core as a result of the flow restriction produced by the A/C evaporator core orifice and the A/C compressor suction.
^ As passenger compartment or outside airflow passes over the plate/fin sections of the A/C evaporator core, the refrigerant inside absorbs the heat and changes into a vapor.
^ A/C compressor suction draws the vaporized refrigerant and oil mixture into the suction accumulator/drier where the heavier oil-laden vapors fall to the bottom and the lighter vapors and oil mixture continue their path to the A/C compressor through the A/C manifold

Refrigerant System:

Refrigerant Systems
These vehicles offer the R-134a A/C system.
^ The R-134 system uses a non-chlorofluorocarbon (non-CFC)-based refrigerant, R-134.
^ R-134 is a Hydrofluorocarbon (HFC)-based refrigerant.

The A/C refrigerant system is a clutch-cycling, orifice tube type. The system components are as follows:
^ A/C compressor
^ A/C clutch
^ A/C condenser core
^ A/C evaporator core
^ Suction accumulator/drier
^ Necessary refrigerant lines

System operation is controlled by the following:
^ A/C evaporator core orifice
^ A/C cycling switch
^ A/C pressure cut-off switch.

The refrigerant system incorporates an A/C compressor controlled by an A/C cycling switch.
The A/C cycling switch:
^ Senses A/C evaporator core pressure to control A/C compressor operation
^ Controls the compressor to stop compressor operation during ambient temperatures below approximately 10°C (50°F) and to prevent A/C evaporator core from icing during normal system operation.

An A/C compressor pressure relief valve is installed in the A/C manifold and tube to protect the refrigerant system against excessive refrigerant pressures.

Operation of the A/C clutch is dependent on signals from the Powertrain Control Module (PCM). The system is programmed to interrupt A/C compressor operation when certain conditions exist. The A/C clutch can be shut off (or kept off) for several seconds:
^ At engine start-up.
^ At high engine speeds.
^ During acceleration.
^ When the engine coolant temperature exceeds a predetermined temperature.
^ During low engine idle conditions (approximately 200 rpm below low idle specifications).