The air conditioning (aircon) system fitted to Defender 1999 MY operates independently of the standard heating and ventilation system. Controlled by 2 switches, the aircon system will only operate when the engine is running and the blower control switch is in at least position ’I’.
Both the blower control and temperature control are 3 position switches. The cooled and dehumidified air produced by the aircon system is directed through vents located in the lower fascia bezel.
The air conditioning system can be used in conjunction with the standard heating and ventilation system. By combining the two separate systems, the required temperature can be maintained over a wide range of ambient temperatures.
Operation
Feed from the battery positive terminal supplies a feed to fusible link 1 and fusible link 5 of the engine compartment fuse box (C0632-1) on a brown wire. Fusible link 5 (C0570-2) supplies a feed to the ignition switch (C0028-1) on a brown/white wire.
Fusible link 1 is wired in series with fusible link 2 of the engine compartment fuse box. Fusible link 2 (C0570-1) in turn, supplies a battery feed to fuses 9 and 10 of the passenger compartment fuse box (C0580-17) on a brown/pink wire. Fuse 9 (C0580-18) is connected to the blower relay (C0153-1) by a brown/purple then brown wire. Fuse 10 (C0580-20) supplies a feed to both the compressor clutch relay (C1268-30) and the cooling fan relay (C0019-30) on brown/slate wires.
When the ignition switch is turned to position ’II’, current flows to fuse 5 (C0580-9) and fuse 3 (C0580-1) of the passenger compartment fuse box on a white wire. Fuse 5 (C0580-10) supplies a feed to the ECM (C0658-33) on a white/green wire.
Fuse 3 of the passenger compartment fuse box (C0580-6) provides a feed to the blower relay (C0153-3) and the air conditioning unit (C1273-11) on white/green wires. The blower relay (C0153-2) is earthed on a blue/black wire and is energised whenever the ignition switch is in position ’II’. This allows a feed from fuse 9 of the passenger compartment fuse box (C0580-18) to flow across the relay (C0153-1 & C0153-4) to the blower motor (C0023-1) on a blue/white wire.
The blower motor (C0023-2) is connected to the blower motor resistor (C0068-2) and the blower motor switch (C1494-5) by blue wires. The blower motor switch (C1494-3) is earthed on a blue/black wire.
With the ignition switch in position ’II’, the main relay (C0063-87) in the engine bay fuse box is energised and provides a feed to both the compressor clutch relay (C1268-85) and the cooling fan relay (C0019-85) on brown/orange wires. The earth path for the compressor clutch relay (C1268-86) is controlled by the ECM (C0658-29) on a black/slate wire. The earth path for the cooling fan relay (C0019-86) is also controlled by the ECM (C0658-4), this time on a black/purple wire.
The ECM receives 2 inputs from the air conditioning system. The trinary switch (C0279-3) provides an input to the ECM (C0658-9) on a black/slate then yellow/slate wire. This input is the aircon clutch request. If granted the ECM provides an earth for the compressor clutch relay. Current can now flow from fuse 10 of the passenger compartment fuse box, across the energised compressor clutch relay (C1268-30 & C1268-87) and supply a feed to the compressor clutch (C0182-1) on a black/green wire. The compressor clutch is earthed (C0182-2) on a black wire.
The second input to the ECM (C0658-23) is the fan request from the air conditioning unit (C1273-1) on a white/black then purple/black wire. This causes the ECM (C0658-4) to earth the cooling fan relay (C0019-86) on a black/purple wire. Current can now flow from fuse 10 of the passenger compartment fuse box, across the energised cooling fan relay (C0019-30 & C0019-87) and supply a feed to the condenser fan (C0280-1) on a black/brown wire. The fan is earthed (C0280-2) on a black wire.