S Only

With the ignition switch in ON (II), voltage is applied to the coil of the A/C compressor clutch relay through fuse 13. When you push the A/C switch ON, and the heater fan switch is in position A, B, C, or D, a "ground" input is provided to the Powertrain or Engine Control Module (PCM with A/T or ECM with M/T) through the A/C thermostat and the A/C pressure switch.

The A/C compressor clutch relay is grounded by the PCM or ECM. When energized, the A/C compressor clutch relay allows battery voltage to turn ON the A/C compressor clutch.