F 350 2WD Super Duty V10-6.8L VIN S (1999)
Refrigerant Pressure Sensor / Switch: Description and Operation
A/C Pressure Switch
A/C Cycling Switch
The A/C cycling switch is mounted on a Schrader valve-type fitting on the side of the suction accumulator/drier.
-
A valve depressor, located inside the threaded end of the A/C cycling switch, presses in on the Schrader valve stem.
-
This allows the suction pressure inside the suction accumulator/drier to control the operation of the A/C cycling switch.
-
The electrical switch contacts open when the suction pressure drops to 152-166 kPa (21-24 psi).
NOTE: A/C cycling pressure switch readings during clutch disengagement (clutch off) may read as high as 186 kPa (27 psi) for a properly
operating switch with a normal calibration of 152-166 kPa (21-24 psi) during clutch disengagement. This may be caused by the pressure reading
being taken from a low side service charge port that is not adjacent (within 177.8 mm/7.0 inches) of the A/C cycling switch. A pressure drop in
the A/C line results in high readings.
-
The contacts close when the suction pressure rises to 269-317 kPa (38-46 psi).
-
When the A/C cycling switch contacts close, the A/C clutch field coil is energized.
-
When the A/C cycling switch contacts open, the A/C clutch field coil is deenergized and 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 will be maintained slightly
above freezing.
-
This prevents icing of the A/C evaporator core and blockage of airflow.
-
It is not necessary to discharge the refrigerant system to remove the A/C cycling switch.
