The air conditioning (A/C) system fitted to Defender operates independently of the standard heating and ventilation system. The A/C system is controlled by two rotary switches located on the driver side of the fascia; one switch controls blower speed, the other controls output temperature.
In order to gain maximum A/C system performance, the standard heater blower control should be set to '0', and both the temperature and distribution controls in the fully up position. The A/C system will then produce cooled and dehumidified air via the lower fascia vents.
NOTE: The A/C system will only operate when the engine is running.
Operation
Power Distribution
Feed from the positive battery terminal (C0192) is supplied to fusible link 1 and fusible link 5 of the under seat fuse box (C0632) on an N wire. Fusible link 1 is connected in series with fusible link 2, which is also located in the under seat fuse box. Fusible link 2 (C0570) provides a feed to fuse 28 and fuse 29 of the passenger compartment fuse box (C0595) on an NK wire.
Fuse 28 (C0595) provides a constant battery feed to the blower motor relay (C0153) on an NP then N wire. Fuse 29 (C0595) provides a constant battery feed to the compressor clutch relay (C1268 on LHD, C0689 on RHD) and the cooling fan relay (C0019) on a pair of NS wires.
Fusible link 5 of the under seat fuse box (C0570) is connected to the ignition switch (C1043 on LHD, C0028 on RHD) by an NW wire. When the ignition switch is turned to the 'ignition' position, current flows across the switch (C1732 on LHD, C0094 on RHD) to fuse 15 and fuse 12 (C0580) of the passenger compartment fuse box on a pair of W wires.
Fuse 15 (C0580) provides an ignition feed to the following on WG wires:
- The blower motor relay (C0153)
- The air conditioning unit (C1273)
- The blower motor switch (C1508)
- The air conditioning temperature control switch (C0275).
Fuse 12 (C0580) provides an ignition feed to the Engine Control Module (ECM) (C0658) on a WG wire.
Blower Motor
The blower motor relay coil (C0153) receives an ignition feed from fuse 15 of the passenger compartment fuse box (C0580) on a WG wire. The relay coil (C0153) is earthed on a UB then B wire. The energised blower motor relay (C0153) provides a feed to the blower motor (C0023) on a UW wire.
Blower Speed 1
When the rotary blower switch is in position 1, current flows across the motor windings (C0023) to the blower motor resistor (C0425) on a U wire. The blower motor resistor (C0425) is connected to the blower motor switch (C1508) by a G wire. As current has to flow through a high resistance rating within the blower motor resistor, the blower motor operates at slow speed. The blower motor switch (C1508) is earthed on a UB then B wire.
Blower Speed 2
When the rotary blower switch is in position 2, current flows across the motor windings (C0023) to the blower motor resistor (C0425) on a U wire. The blower motor resistor (C0425) is connected to the blower motor switch (C1508) by an NY wire. As current has to flow through a lower resistance rating within the blower motor resistor, the blower motor operates at increased speed. The blower motor switch (C1508) is earthed on a UB then B wire.
Blower Speed 3
When the rotary blower switch is in position 3, current flows across the motor windings (C0023) directly to the blower motor switch (C1508) on a U wire. As the blower motor resistor is by-passed, the blower motor operates at fast speed. The blower motor switch (C1508) is earthed on a UB then B wire.
Engine Control Module
The air conditioning unit (C1273) monitors blower motor operation on a U wire. When the motor is operational, the air conditioning unit (C1273) provides a feed to the Engine Control Module (ECM) (C0658) on a WB then PB wire.
Temperature Control
The temperature control switch relays operator input to the air conditioning unit, to control A/C system temperature output. The switch (C0275) receives an ignition feed from fuse 15 of the passenger compartment fuse box (C0580) on a WG wire.
When the switch is turned to position 1, a feed is provided to the air conditioning unit (C1273) on a UY wire. When the switch is turned to position 2, a feed is provided to the air conditioning unit (C1273) on a RW wire. When the switch is turned to position 3 (maximum cooling), a feed is provided to the air conditioning unit (C1273) on a B wire.
The switch (C1273) is earthed on a UB then B wire.
Evaporator Temperature Sensor
The evaporator temperature sensor is used to ensure the evaporator doesn't freeze. The air conditioning unit (C1273) provides a feed to the temperature sensor (C0134) on a K wire, and receives a return signal on a UW wire. The air conditioning unit (C1273) is earthed on a UB then B wire.
Compressor Clutch
When A/C is requested, the air conditioning unit (C1273) provides a feed to the Engine Control Module (ECM) (C0658) via the pressure switch (C0279) on a UG then BS then YS wire. If the pressure within the high pressure side of the A/C system is within operational limits, the ECM energises the compressor clutch relay.
The compressor clutch relay coil (C0689) receives a feed from the energised main relay (C0063) on an NO wire. To energise the compressor clutch relay the ECM (C0658) provides an earth path for the relay coil (C0689) on a BS wire.
The energised compressor clutch relay (C0689) provides a feed to compressor clutch (C0182) on a BG wire. The compressor clutch (C0182) is earthed on a B wire.
Condenser Fan
The cooling fan relay coil (C0019) is provided a feed by the energised main relay (C0063) on an NO wire. To energise the cooling fan relay, the ECM (C0658) provides an earth path for the relay coil (C0019) on a BP wire. The energised cooling fan relay (C0019) is now able to provide a feed to the condenser fan motor (C0280) on a BN wire. The motor (C0280) is earthed on a B wire.