Circuit Operation

Description
The heater is operated from three rotary controls located in the center console. Two of the controls operate the temperature and air flow distribution. The third control operates the four speed blower motor.

A resistor pack is mounted on the RH side of the heater unit. The resistor pack supplies reduced voltages to the blower motor for fan speed one, two, and three. Fan speed four drives the blower motor at full speed with a direct 12 V supply.

The blower motor will only operate when the ignition switch is in the 'ignition' position.

Operation
Feed from the positive battery terminal (C0192) is supplied to fusible link 1 of the engine compartment fuse box (C0632) on an R wire. Fusible link 1 is connected in series with fuse 8 and fusible link 2, which are also located in the engine compartment fuse box.

Fusible link 2 (C0571) is connected to the ignition switch (C0028) by an NR wire. When the ignition switch is turned to the 'ignition' position, current flows across the switch (C0028) to fuse 4 of the passenger compartment fuse box (C0588) on an SU wire. Fuse 4 (C0585) provides an ignition feed to the following on G then LGS wires:
- The fresh/recirculated air motor (C0006).
- The fresh/recirculated air switch (C0750).
- The blower motor switch (C0058).

Blower Speed 1
If blower speed 1 is selected, current flows across the blower motor switch (C0058) to the resistor pack (C0425) on an RK wire. The resistor pack (C0425) is connected to the blower motor (C0056) by a GK then G wire. As current has to flow through the greatest value resistor, the blower motor operates at slow speed.

The blower motor (C0056) is earthed on a B wire.

Blower Speed 2
If blower speed 2 is selected, current flows across the blower motor switch (C0058) to the resistor pack (C0425) on an RY wire. The resistor pack (C0425) is connected to the blower motor (C0056) by a GK then G wire. As current has to flow through the medium value resistor, the blower motor operates at a slightly increased speed.

Blower Speed 3
If blower speed 3 is selected, current flows across the blower motor switch (C0058) to the resistor pack (C0425) on an RG wire. The resistor pack (C0425) is connected to the blower motor (C0056) by a GK then G wire. As current has to flow through the smallest value resistor, the blower motor operates at an increased speed.

Blower Speed 4
If blower speed 4 is selected, current flows across the blower motor switch (C0058) to the blower motor relay coil (C0153) on an RS wire. The relay coil (C0153) is earthed on a BS then B wire. The energised blower relay allows a feed from fuse 8 of the engine compartment fuse box (C0576) across the closed relay switch (C0153) directly to the blower motor (C0056) on a GR then G wire. As current by-passes the resistor pack, the blower motor operates at high speed.

Fresh/Recirculated Air
Fuse 4 of the passenger compartment fuse box (C0586) provides an ignition feed to the fresh/recirculated air motor (C0006) and the fresh/recirculated air switch (C0750) on G then LGS wires. When the switch is the normal (released) position, it provides an earth path for the motor (C0006) via a Y wire. The motor will open the recirculation flap, allowing the heater to use air drawn from outside the vehicle.

If the fresh/recirculated air switch is pressed, it provides an earth path for the motor (C0006) via a K wire. The motor will now close the recirculation flap, allowing the heater system to use recirculated air. The switch is mounted on the center console and is earthed (C0750) on a B wire.