Air Conditioning Clutch Switch
WARNING: This page does not describe the selected car, but rather 11 other vehicles, including the 2002 Mercury Grand Marquis, 2002 Lincoln Town Car, 2002 Ford Crown Victoria, 2001 Mercury Mountaineer, and 2001 Mercury Grand Marquis. However, it is still accessible from the selected car via links, so may be relevant.
On factory installed A/C system, PCM receives signal voltage from Air Conditioning Clutch (ACC) switch located on accumulator drier. This switch indicates if air conditioning compressor clutch is engaged. The PCM uses the ACC switch signal to adjust EPC pressure to compensate for additional engine load. If the ACC switch fails with closed contacts, line pressure will be slightly low with air conditioning off. If the ACC switch fails with open contacts, line pressure will be slightly high with air conditioning on.