RAM 2500 Truck 2WD L6-5.9L DSL Turbo VIN C (2002)
Low Pressure Sensor / Switch: Description and Operation
A/C LOW PRESSURE SWITCH
The a/c 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 a/c low pressure switch is connected in series electrically with the a/c high pressure switch and the a/c heater control, 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 evaporator temperature prevents condensate water on the evaporator fins
from freezing and obstructing air conditioning system air flow.
The a/c low pressure switch contacts are open when the suction pressure is about 152-165 kPa (22-24 psi) or lower. The switch contacts will close when
the suction pressure rises to about 255-296 kPa (37-43 psi) or above. Lower ambient temperatures, below about -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 a/c low pressure switch is a factory-calibrated unit. It cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.
