DESCRIPTION AND OPERATION
4.18
DEFENDER 1999 MY
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.