Refrigerant Pressure Sensor / Switch: Description and Operation

A/C Pressure Transducer

The A/C pressure transducer monitors the compressor discharge pressure and communicates with the powertrain control module (PCM). The PCM will interrupt A/C compressor operation in the event that the A/C pressure transducer indicates high system discharge pressures. It is also used to sense no or low charge conditions. If the pressure is below a predetermined value for a given ambient temperature, the PCM will not allow the clutch to engage.

The A/C pressure transducer is mounted on a Schrader-type valve fitting on the A/C compressor to condenser discharge line.

A valve depressor, located inside the threaded end of the A/C pressure transducer, presses on the Schrader valve stem and allows the A/C pressure transducer to monitor the compressor discharge pressure.

When the compressor discharge pressure rises to approximately 2,896 kPa (420 psi), the PCM will interrupt the A/C compressor clutch coil circuit and disengage the A/C compressor.

When the pressure drops to approximately 1,724 kPa (250 psi) the PCM will enable the A/C compressor circuit.

It is not necessary to discharge the refrigerant system to remove the A/C pressure cut-off switch. Controls the signal to the pcm to control the fan speed.