Compressor Cut-Off/Cycling Switchs

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

OPERATION
The electrical switch contacts will open when the suction pressure drops to 152-193 kPa (22-28 psi). The contacts will close when suction pressure increases to 276-324 kPa (40-47 psi). Ambient temperatures below approximately 7-10° C (45-50° F), during cold weather seasons, prevents the A/C cycling switch contacts from closing. This is due to the pressure/temperature relationship of the refrigerant and the requirement of the system pressure to reach 276-324 kPa (40-47 psi) to close the A/C cycling switch contacts.

These contacts control the electrical circuit to the A/C clutch field coil. When the A/C cycling switch contacts close, the signal to energize the A/C clutch is sent to the Constant Control Relay Module (CCRM). The CCRM then supplies the voltage to energize the A/C clutch for A/C compressor operation. When the A/C cycling switch contacts open, the CCRM opens the A/C clutch electrical circuit to de-energized the A/C clutch and the A/C compressor operation stops.

The A/C cycling switch will control the A/C evaporator core pressure at a point where the plate/fin surface temperature is maintained slightly above freezing. This prevents A/C evaporator core icing and the blockage of airflow.