A/C High Pressure Switch
WARNING: This page does not describe the selected car, but rather 31 other vehicles, including the 2003 Mercury Sable, 2003 Mercury Mountaineer, 2003 Mercury Marauder, 2003 Mercury Grand Marquis, and 2003 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
The A/C high pressure switch is used for additional A/C system pressure control. A/C high pressure switch is either dual function for 2-speed fan control applications or single function for all other applications. For refrigerant containment control, the normally closed high pressure contacts open at a predetermined A/C pressure. This will result in A/C turning off, preventing A/C pressure from rising to a level that would open 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 Powertrain Control Module (PCM). The PCM will then turn on the high speed fan to help reduce A/C pressure.