Air Conditioning High Pressure Switch

Location
In the line from the compressor to the condenser.

Function
Protection of the air conditioning system against a pressure overload by cutting out the compressor.

Description
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 two-speed 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 will result 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 will then turn on the high speed fan to help reduce the pressure.

Operation
The function of the high pressure switch is to protect the high pressure section of the refrigerant circuit. When pressure exceeds the maximum value of 29,6 bar (2965 kPa, 430 psi) because, for instance, the air flow through the condenser is impeded or the high pressure line is blocked, the high pressure switch switches the compressor off.

Only when the pressure has fallen once more to 22,4 bar (2241 Kpa, 325 psi) bar is the compressor switched on again. At a pressure level of 22,4 bar (2241 kPa, 325 psi) the PCM switches to high blower speed.

Only when the pressure has fallen once more to 17,2 bar (1717 kPa, 249 psi) does the PCM switch to low blower speed.

For additional information, refer to Wiring Diagrams.