Grand Cherokee 2WD L6-242 4.0L VIN S MFI (1993)
Low Pressure Sensor / Switch: Description and Operation
Fig.7 Accumulator And Clutch Cycling Pressure Switch
A valve depressor, is located inside the threaded end of the pressure switch. It presses in on the Schrader-Type valve stem as the switch is mounted and
allows the suction evaporator outlet pressure inside the accumulator canister to control switch operation. The electrical switch contacts are normally open
when the suction evaporator outlet pressure is approximately 172 kPa(25 psi) or lower. They will close when the suction evaporator outlet pressure rises
to approximately 296 kPa(43 psi) or above. Lower ambient temperatures, below approximately -1 °C(30 °F) during cold weather will also open the
clutch cycling pressure switch contacts. This is due to the pressure/temperature relationship of the refrigerant in the system. The electrical switch contacts
control the electrical circuit to the compressor 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 compressor magnetic clutch coil is de-energized.
- The A/C clutch is disengaged.
- The compressor does not operate.
The clutch cycling pressure switch, when functioning properly, will control the evaporator core refrigerant flow. This is at a point where the plate/fin
surface temperature will be maintained slightly above freezing. This also prevents evaporator icing and the blockage of airflow.
