Front Air Conditioning
Air temperature control ECU supply
A feed from fusible link 3 in the engine compartment fusebox is connected on an NR wire to the passenger compartment fusebox. The feed passes through fuse 20 and is connected, via header C0725, to the Air Temperature Control ECU on a P wire.
Main relay/inertia switch supply
A feed from fuse 13 in the engine compartment fusebox is connected to the inertia switch by a NB wire. When the inertia switch is closed (not tripped), the feed continues on a WG wire to the coil of the main relay in the engine compartment fusebox. The main relay coil is then connected from the relay to the Engine Control Module (ECM)) on a UR wire. When conditions are correct, the ECM provides the earth path which in turn energizes the main relay, closing the contacts.
Cooling fan relay supply
A feed from fuse 5 in the engine compartment fusebox, is connected to the contacts of the cooling fan relay.
Cooling fan motor operation
When the main relay is energized, a feed passes from the relay contacts to the coil of the cooling fan relay. The cooling fan relay coil is earthed on a BP wire (Td5 engines) or a GW wire (V8 engines) to the ECM.
When conditions are correct, the ECM provides the earth path which energizes the cooling fan relay coil closing the contacts. The feed from fuse 5 in the engine compartment fusebox passes through the cooling fan relay contacts and from the fusebox to the cooling fan motor on a BN wire. The feed operates the cooling fan motor which is connected to earth header C0018 on a B wire.
Air conditioning compressor clutch relay supply
A feed from fuse 6 in the engine compartment fusebox, is connected to the contacts of the air conditioning compressor clutch relay.
Air conditioning compressor clutch operation
When the main relay is energized, a feed passes from the relay contacts to the coil of the air conditioning compressor clutch relay. The compressor clutch relay coil is earthed on a BS wire to the ECM.
When conditions are correct, the ECM provides the earth path which in turn energizes the compressor clutch relay coil closing the contacts. The feed from fuse 6 in the engine compartment fusebox passes through the relay contacts and from the fusebox is connected on a BG wire to the air conditioning compressor clutch. The feed operates the air conditioning compressor clutch which is connected to earth header C0018 (Td5 engines) or earth eyelet connector C0807-1 (V8 engines).
Fresh/recirculated air mode motor
The feed from fuse 31 in the passenger compartment fusebox passes on a GK wire to splice joint A9/A144. From the splice joint the feed passes on a GR wire to connector interface C0265-1/C0778-1. From the connector interface the feed passes, via splice joint A1, to the fresh/recirculated air mode motor on a LGW wire.
The fresh/recirculated air mode motor is connected to the Air Temperature
Control (ATC) ECU on an RG wire to ECU pin C0793-6 and on a UB wire to ECU pin C0793-16.
Blower relay
The feed from fuse 31 in the passenger compartment fusebox passes on a GK wire to splice joint A9/A144. From the splice joint the feed passes on a GR wire to connector interface C0265-1/C0778-1. From the connector interface the feed passes, via splice joint A1, to the coil of the blower relay. The coil is connected on an N wire to pin C0793-2 of the ATC ECU.
When blower relay (R176) operation is required, the ATC ECU completes an earth path for the relay coil, energizing the relay and closing the contacts. A feed from fuse 7 in the passenger compartment fusebox is connected on an NR wire to contacts of the blower relay. The feed passes through the relay contacts and is connected on a WR wire to the front blower motor. The front blower motor is connected on a B wire to the power relay and the power transistor via splice joint A10.
The contact of the blower relay is also connected on a B wire, via splice joint B9, to earth eyelet connector C0910-1. When the relay is connected to the earth, the front blower motor power feed will be removed preventing motor operation.
Power relay
The coil of the power relay receives a feed from fuse 31 in the passenger compartment fusebox. The feed passes on a GK wire to splice joint A9/A144. From the splice joint the feed passes on a GR wire to connector interface C0265-1/C0778-1. From the connector interface the feed passes, via splice joint A1, to the coil of the power relay. The coil is connected to pin C0793-10 on the ATC ECU.
The power relay operates speed 31 of the blower motor. This fastest motor speed is operated by the ATC ECU granting the earth path for the power relay coil. The energized coil closes the relay contacts and allows the earth for the front blower motor to pass via splice joint A10, through the contacts. The earth path is completed on a B wire, via splice joints A9 and B9, to earth eyelet connector C0910-1.
Power transistor
The power transistor controls speeds 1 to 30 of the front blower motor. The power transistor is controlled by the ATC ECU on a PG wire to ECU pin C0792-8 and on a G wire to ECU pin C0793-1.
Speeds 1 to 30 are controlled by the power transistor varying the resistance to the earth flow from the front blower motor. The earth path from the front blower motor is connected on a B wire, via splice joint A10, to the power transistor. The power transistor is connected on a B wire via splice joints A9 and B9, to earth eyelet connector C0910-1.
Air Temperature Control (ATC) ECU
The ATC ECU is connected from ECU pin C0792-2 to the SLABS ECU pin C0504-3 on a KG wire via header C0290. The SLABS ECU provides a speed signal to the ATC ECU for blower speed control.
On V8 engine vehicles, the ECM is connected on a PW wire to ATC ECU pin C0793-12.
On Td5 engine vehicles, the ECM is connected on a GO wire to ATC ECU pin C0793-9.
On all vehicles, the ATC ECU is connected from pin C0791-4 on a B wire, via header C0725, to earth header C0017 LHD/C0018 RHD.
Air conditioning (A/C) cut-off switch
The A/C cut-off switch is a high/low pressure switch fitted into the A/C system.
When the switch is operated, the ECM signals the ATC ECU to request the air conditioning compressor clutch relay to be de-energized.
The ATC ECU is connected from ECU pin C0793-11 on a YB wire to the A/C cut-off switch. The A/C cut-off switch is connected on a YS wire, via header C0290 (LHD only), to the ECM.
In-car temperature sensor
The in-car temperature sensor receives a feed from fuse 31 in the passenger compartment fusebox. The feed passes on a GK wire to splice joint A9/A144. From the splice joint the feed passes on a GR wire to the in-car temperature sensor and is connected to a motor which draws air over the sensor. The motor is connected on a B wire from the in-car temperature sensor, via header C0760, to earth header C0017 LHD/C0018 RHD.
A reference voltage from the ATC ECU pin C0791-8 is connected on a BW wire, via header C0725 to the in-car temperature sensor. An input from the sensor is connected on a WB wire to the ATC ECU pin C0792-7.
Ambient Air Temperature (AAT) Sensor
A reference voltage from the ATC ECU pin C0791-8 is connected on a BW wire, via header C0725 to the AAT sensor. An input from the sensor is connected on a YG wire to the ATC ECU pin C0792-6.
Heater Coolant Temperature (HCT) Sensor
A reference voltage from the ATC ECU pin C0791-8 is connected on a BW wire, via header C0725 and splice joints A26, B26, C26 and D26 to the HCT sensor. An input from the sensor is connected on an RB wire to the ATC ECU pin C0792-5.
Evaporator sensor
A reference voltage from the ATC ECU pin C0791-8 is connected on a BW wire, via header C0725 and splice joints A26, B26, C26 and D26 to the evaporator sensor. An input from the sensor is connected on a PB wire to the ATC ECU pin C0792-18.
Sunlight sensor
A reference voltage from the ATC ECU pin C0791-3 is connected on a GW wire, via splice joint A278, to the sunlight sensor. Two inputs from the sunlight sensor are connected on WU and WR wires to ATC ECU pins C0792-16 and C0792-17 respectively.
Air Temperature mode motor - LH
A reference voltage from the ATC ECU pin C0791-8 is connected on a BW wire, via header C0725 and splice joints A266 and 826 to the LH air temperature mode motor.
A reference voltage from the ATC ECU pin C0791-3 is connected on a GW wire to splice joint A278. From the splice joint the reference voltage continues on a GR wire, through splice joint A22 to the LH air temperature mode motor.
An input from the LH air temperature mode motor is passed to pin C0792-14 on the ATC ECU on an SU wire.
Two outputs from ATO ECU pins C0793-14 and C0793-6 are connected to the LH air temperature mode servo motor on GU and UC wires respectively. Each output drives the servo motor to blend hot or cold air.
Air temperature mode motor - RH
A reference voltage from the ATC ECU pin C0791-8 is connected on a BW wire, via header C0725 and splice joints A26, B26 and C26 to the RH air temperature mode motor.
A reference voltage from the ATC ECU pin C0791-3 is connected on a GW wire to splice joint A278. From the splice joint the reference voltage continues on a GR wire, through splice joint A22 and B22 to the RH air temperature mode motor.
An input from the RH air temperature mode motor is passed to pin C0792-15 on the ATC ECU on a YG wire.
Two outputs from ATC ECU pins C0793-13 and C0793-5 are connected to the RH air temperature mode servo motor on Y and PY wires respectively. Each output drives the servo motor to blend hot or cold air.
Air distribution mode motor
A reference voltage from the ATC ECU pin C0791-8 is connected on a BW wire, via header C0725 and splice joint A26 to the air distribution mode motor.
A reference voltage from the ATC ECU pin C0791-3 is connected on a GW wire to splice joint A278. From the splice joint the reference voltage continues on a GR wire, through splice joint A22 and B22 to the air distribution mode motor.
An input from the air distribution mode motor is passed to pin C0792-4 on a UY wire.
Two outputs from ATC ECU pins C0793-15 and C0793-7 are connected to the air distribution servo motor on US and UW wires respectively. Each output drives the servo motor to the windscreen demist or footwells position.