900 L4-2118cc 2.1L DOHC (1992)
Compressor HVAC: Description and Operation
Operation
Compressor 170 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 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. (When the switch is not
activated, the lamp is supplied from the instrument lighting rheostat.)
Compressor 170 and ordinary radiator fan 37 are connected via relay 156, whose contacts are supplied from fuse 25. The relay will be energized 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.
When the relay is energised, the compressor will be supplied only if temperature switch 168 is closed. (The switch will open if the engine temperature
should exceed about +115°C.)
Diode 173, which is connected in parallel with the compressor, reduces the voltage transients at the instant when the compressor is switched off.
Delayed Connection When Starting
Relay 156 is equipped with two time delay functions. One of them is activated whenever the engine is being started. Ignition switch 20 (in the start
position) supplies pin 50, and if switch 169 is then depressed, the energizing of the relay and thus starting of the compressor will be delayed for about 10
seconds, to ensure that combustion in the engine will be stable after starting, before the the AC load is applied.