Compressor HVAC: Description and Operation

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 Engine Control Module (ECM) through the A/C thermostat and the A/C pressure switch.

The A/C compressor clutch relay is grounded by the Engine Control Module (ECM). When energized, the A/C compressor clutch relay allows battery voltage to turn ON the A/C compressor clutch.

Si, SR, 4WS, VTEC, SR-V
Battery voltage is supplied through fuse 45 to the A/C compressor clutch relay contacts at all times.

With the ignition switch in ON (II), voltage is applied to the coil of the A/C compressor clutch relay through fuse 11. 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 ECM through the A/C thermostat and the A/C pressure switch.

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