PT Cruiser L4-2.4L Turbo VIN 8 (2005)
Low Pressure Sensor / Switch: Description and Operation
The A/C low pressure switch is a single pole, single throw, pressure actuated switch that is used to control evaporator freeze up.
The A/C low pressure switch is mounted on a fitting located on the top of the A/C accumulator. The A/C low pressure switch fitting on the accumulator
is equipped with an O-ring and contains a Schrader-type valve, which allows the switch to be serviced without discharging the refrigerant system.
The A/C low pressure switch is electrically connected in series with the A/C-heater control and the A/C high pressure switch, between ground and the
powertrain control module (PCM) or the engine control module (ECM), depending on engine application.
The A/C low pressure switch contact opens or closes the path the ground, signaling the PCM or ECM to turn the A/C compressor clutch on and off. This
regulates the refrigerant system pressure and controls evaporator coil temperature. Controlling the 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 A/C suction line pressure is approximately 152 kPa (22 psi) or lower. The A/C low pressure
switch contacts will close when the A/C suction line pressure rises to approximately 234 to 262 kPa (34 to 38 psi) or above. Lower ambient
temperatures, below approximately -1° C (30° F), will also cause the A/C low pressure 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 factory-calibrated and cannot be adjusted or repaired. If the A/C low pressure switch is faulty or damaged, it must be
replaced.
