Compressor HVAC: Description and Operation

Compressor And Radiator Fan Motor 37

The AC can be switched on and off by means of AC switch 169, which is supplied from fuse 6, via the 29-pole black connector 152C. When the switch is depressed, the lamp built into the button will be supplied directly (not via the resistor), so it will light up with full intensity.

Compressor 170 and ordinary radiator fan 37 are connected via relay 156, which is supplied from fuse 25. The relay will be energised when the following conditions are satisfied:

- Pressure switch 166 is closed, i.e. the refrigerant pressure is at least 2.8 bar.

- Anti-freeze thermostat (cycling clutch contact) 171 is closed, i.e. the ambient temperature is at least about +6 °C.

- Throttle switch 167 is closed, i.e. the butterfly valve is not open more than 70° (if the jumper is cut).

- Temperature switch 168 is closed. (The switch will open if the engine temperature exceeds around +115 °C.)

Solenoid valve 142, which raises the engine idling speed, is connected in parallel with the compressor and the radiator fan. Diode 173 reduces the voltage transients at the instant when the compressor is switched off.

AC Radiator Fan 172
Extra radiator fan 172 for the AC is connected via relay 155 and is supplied from fuse 6.

The relay coil is supplied from the contacts of relay 156 and from pressure switch 166. The AC radiator fan thus runs when AC switch 169 is depressed and pressure switch 166 is closed.