Ranger 2WD V6-245 4.0L VIN X SFI (1997)
Refrigerant Pressure Sensor / Switch: Description and Operation
A/C Pressure Switch
The A/C cycling switch is mounted on a Schrader-type valve fitting on the top of the suction accumulator/drier assembly. A valve depressor, located
inside the threaded end of the A/C cycling switch, presses in on the Schrader valve stem as the A/C cycling switch is mounted and allows the suction
pressure inside the accumulator/drier housing to activate the A/C cycling switch. The electrical contacts are normally open when the suction pressure is
at or below 169 kPa (23 +/- 1 psi); they will close, activating the A/C clutch, when the suction pressure rises to approximately 275-324 kPa (40-47 psi)
or above. Lower ambient temperatures (below approximately 7°C or 45°F), during cold weather, will prevent the contacts from closing, due to the
pressure/temperature relationship of the refrigerant in the system. The electrical contacts control the electrical circuit to the A/C clutch field coil. When
the contacts are closed, the A/C clutch field coil is energized and the A/C clutch is engaged to drive the compressor. When the contacts are open, the A/C
clutch field coil is de-energized, the A/C clutch is disengaged and the compressor does not operate. The A/C cycling switch, when functioning properly,
will control the pressure at a point where the plate/fin surface temperature will be maintained slightly above freezing which prevents icing and the
blockage or airflow.
