Compressor Cycling Switch
WARNING: This page is about a different car, the 2002 Mercury Villager. However, it is still accessible from the selected car via links, so may be relevant.
Compressor cycling switch is located on top of accumulator-drier and monitors refrigerant pressure. This information is sent to Powertrain Control Module (PCM). When low pressure is about 21-23 psi (1.5-1.6 kg/cm2 ), switch contacts open, and compressor (magnetic) clutch coil is de-energized. When low pressure increases to about 42 psi (3.0 kg/cm2 ) or more, switch contacts close, and compressor clutch coil is energized.
Ambient temperatures less than 48°F (9°C) will prevent low pressure from increasing enough to close switch contacts. Proper operation of compressor cycling switch prevents evaporator icing, which would block airflow through evaporator fins.