Refrigerant Pressure Sensor / Switch: Description and Operation

The dual function pressure switch is used to interrupt A/C compressor operation in the event of high system discharge pressures.
- The dual function pressure switch is mounted on a schrader valve-type fitting on the compressor manifold and tube assembly.
- It is not necessary to recover the refrigerant to install a new dual function pressure switch.
- A valve depressor, located in the threaded end of the dual function pressure switch, presses on the valve stem. This allows the dual function pressure switch to monitor the compressor discharge pressure.
- When the compressor discharge pressure rises, the switch contacts open, disengaging the A/C compressor. When the compressor discharge pressure drops, the switch contacts close to allow operation of the A/C compressor.
- The dual function pressure switch has a second set of electrical contacts used for high-speed cooling fan control. When the compressor discharge pressure rises, the contacts close and engage the high-speed cooling fan control. When the pressure drops, the contacts open and the high-speed cooling fan control is disengaged.