Grand Marquis V8-302 5.0L VIN F TBI (1984)
Refrigerant Pressure Sensor / Switch: Description and Operation
DESCRIPTION AND OPERATION
The clutch cycling pressure switch will control the evaporator core pressure at a point where the plate/fin surface temperature will be maintained slightly
above freezing which prevents evaporator icing and the blockage of air flow.
A valve depressor, located inside the threaded end of the pressure switch, presses in on the schrader valve stem as the switch is mounted and allows the
suction pressure inside the accumulator/drier housing to control switch operation. The electrical switch contacts are normally open when the suction
pressure is at or below 168 kPa (24.5 psi); they will close when the suction pressure rises to approximately 324 kPa (47 psi) or above. Lower ambient
temperatures (below 10° C or 50° F), during winter cold weather seasons, will also open the clutch cycling pressure switch contacts due to the
pressure/temperature relationship of the refrigerant in the system. The electrical switch contacts control the electrical circuit to the compressors magnetic
clutch coil. When the switch contacts are closed, the clutch coil is energized and the A/C clutch is engaged to drive the compressor. When the switch
contacts are open, the compressors magnet clutch coil is de-energized, the A/C clutch is disengaged and the compressor does not operate.
