Grand Cherokee 4WD V8-4.7L VIN N (2000)
Low Pressure Sensor / Switch: Description and Operation
LOW PRESSURE SWITCH
The low pressure switch is located on the top of the accumulator. The switch is screwed onto an accumulator fitting that contains a Schrader-type
valve, which allows the switch to be serviced without discharging the refrigerant system. The accumulator fitting is equipped with an O-ring to seal
the switch connection.
The low pressure switch is connected in series electrically with the high pressure switch, between ground and the Powertrain Control Module
(PCM). The switch contacts open and close causing the PCM to turn the compressor clutch on and off. This regulates the refrigerant system
pressure and controls evaporator temperature. Controlling the evaporator temperature prevents condensate water on the evaporator fins from
freezing and obstructing air conditioning system air flow.
The low pressure switch contacts are open when the suction pressure is approximately 152 kPa (22 psi) or lower. The switch contacts will close
when the suction pressure rises to approximately 234 - 262 kPa (34 - 38 psi) or above. Lower ambient temperatures, below approximately -1 °C
(30 °F), will also cause the switch contacts to open. This is due to the pressure/temperature relationship of the refrigerant in the system.The low
pressure switch is a factory-calibrated unit. It cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.
