RAM 3500 Truck 4WD L6-5.9L DSL Turbo VIN C (2002)
High Pressure Sensor / Switch: Description and Operation
A/C HIGH PRESSURE SWITCH
The a/c high pressure switch is located on the discharge line near the compressor. The switch is screwed onto a fitting that contains a Schrader-type
valve, which allows the switch to be serviced without discharging the refrigerant system. The discharge line fitting is equipped with an O-ring to seal the
switch connection.
The a/c high pressure switch is connected in series electrically with the a/c low 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 prevents compressor operation when the
discharge line pressure approaches high levels.
The a/c high pressure switch contacts are open when the discharge line pressure rises above about 3100 - 3375 kPa (450 - 490 psi). The switch contacts
will close when the discharge line pressure drops to about 1860 - 2275 kPa (270 - 330 psi). When checking refrigerant system pressures with a manifold
gauge set, keep in mind that the indicated pressures will be about 172 kpa (25 psi) below the actual switch pressure values due to the pressure drop that
occurs in the refrigerant system between the switch and the high pressure service port.
The a/c high pressure switch is a factory-calibrated unit. The switch cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.
