Compressor Cut-Off/Cycling Switchs

Accumulator/Drier:

DESCRIPTION
The A/C cycle switch is mounted on a Schrader valve-type fitting on the top of the suction accumulator/drier assembly. A valve depressor, located inside the threaded end of the A/C cycle switch, presses the Schrader valve stem down as the A/C cycle switch is mounted. This allows the suction pressure inside of the suction accumulator/drier to act on the A/C cycle switch.

OPERATION
The A/C cycle switch contacts open when the suction pressure drops to 22-28 psi. The contacts will close when suction pressure increases to 276-324 kPa (40-47 psi). When ambient temperatures are below approximately 50° F during cold weather seasons the A/C cycle switch contacts will not close. This is due to the pressure/temperature relationship of the refrigerant and the requirement of the system pressure to reach the pressure required to close the A/C cycle switch contacts.

The A/C cycle switch contacts control the electrical circuit to the A/C compressor clutch field coil. When the A/C cycle switch contacts close, the signal to energize the A/C clutch is sent to the Constant Control Relay Module (CCRM) from the powertrain control module (PCM). The CCRM then supplies the voltage to energize the A/C clutch for A/C compressor operation. When the pressure switch contacts open, the PCM tells the CCRM to open the clutch electrical circuit to de-energize the A/C clutch and A/C compressor operation stops. The clutch cycling switch, when functioning properly, controls the A/C evaporator core pressure at a point where the plate/fin surface temperature is maintained slightly above freezing which prevents the A/C evaporator core icing and the blockage of airflow.