Refrigerant Pressure Sensor / Switch: Description and Operation

Air Conditioning (A/C) Cycling Switch
The A/C cycling switch may be wired to either the ACCS or ACPSW PCM input. When the A/C cycling switch opens, the PCM turns off the A/C clutch. For information on the specific function of the A/C cycling switch, refer to Heating and Air Conditioning, Climate Control System Air Conditioning System Overview. Also, refer to the applicable Vehicle/Diagrams for vehicle specific wiring.

If the ACCS signal is not received by the PCM, the PCM circuit will not allow the A/C to operate.

Some applications do not have a dedicated (separate) input to the PCM indicating that A/C is requested. This information is received by the PCM through the communication link.

Air Conditioning (A/C) High Pressure Switch
The A/C high pressure switch is used for additional A/C system pressure control. The A/C high pressure switch is either dual function for multiple speed, relay controlled electric fan applications, or single function for all others.

For refrigerant containment control, the normally closed high pressure contacts open at a predetermined A/C pressure. This results in the A/C turning off, preventing the A/C pressure from rising to a level that would open the A/C high pressure relief valve.

For fan control, the normally open medium pressure contacts close at a predetermined A/C pressure. This grounds the ACPSW circuit input to the PCM. The PCM then turns on the high speed fan to help reduce the pressure.

For additional information, refer to Heating and Air Conditioning, Climate Control System, Air Conditioning System Overview or Vehicle/Diagrams.

Air Conditioning Pressure (ACP) Transducer Sensor

A/C Pressure Transducer Sensor Output Voltage:

Typical ACP Transducer Sensor:

The ACP transducer sensor is located in the high pressure (discharge) side of the A/C system. The ACP transducer sensor provides a voltage signal to the PCM that is proportional to the A/C pressure. The PCM uses this information for A/C clutch control, fan control and idle speed control.