RAM 2500 Truck 2WD L6-359 5.9L DSL Turbo VIN D FI (1997)
Low Pressure Sensor / Switch: Description and Operation
Fig 28 Low Pressure Cycling Clutch Switch
LOW PRESSURE CYCLING CLUTCH SWITCH
The low pressure cycling clutch switch is mounted on top of the accumulator. The switch is connected in series with the high pressure cut-off
switch in the A/C request signal circuit, between the heater-A/C mode control switch 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 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 switch contacts are normally open when the suction pressure is approximately 172 kPa (25 psi) or lower. The switch will close when the
suction 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 switch contacts. This is due to the
pressure/temperature relationship of the refrigerant in the system.
The low pressure cycling clutch switch is a factory-calibrated unit. This switch cannot be adjusted or repaired. If faulty or damaged, the switch
must be replaced.
