Dual Function Pressure Switch

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-type valve fitting on the condenser-to-evaporator tube.
• A valve depressor, located inside the threaded end of the dual function pressure switch, presses on the Schrader valve stem.
• This allows the dual function pressure switch to monitor the compressor discharge pressure.
• It is not necessary to recover the refrigerant to remove the dual function pressure switch.
• The dual function pressure switch has 2 sets of contacts. One electrical contact is normally closed.
• When the compressor discharge pressure rises, the switch contacts open, interrupting the 12 volt A/C request (ACCS) signal to the PCM and disengaging the A/C compressor. When the pressure drops, the contacts close, completing the 12 volt A/C request (ACCS) signal to the PCM and enabling the A/C compressor.

The switch contains a second set of electrical contacts used for high-speed fan control.

• When the compressor discharge pressure rises, the contacts close and send a 12 volt signal (ACPSW) to the PCM requesting high speed cooling fan operation. When the pressure drops, the contacts open and the 12 volt signal is interrupted.