Cooling Fan Control Unit – 02MY

Cooling Fan Control Unit – 02MY

Fusible link 5 of the engine compartment fuse box (C0573) provides a constant battery feed to the cooling fan control unit (C0208) on an NG wire. Fuse 4 of the engine compartment fuse box (C0575) provides a feed to the cooling fan control unit (C1680) on an NK wire when the main relay in energised. The cooling fan control unit (C0208) is earthed on a B wire.

To control cooling fan and condenser fan speed, the ECM (C0913 on K Series vehicles, C0371 on KV6 vehicles) provides the cooling fan control unit (C1680) a Pulse Width Modulated (PWM) signal on a UW wire (UR then UW on KV6 vehicles). The frequency of the pulses supplied by the ECM determines the speed the cooling fan control unit will drive the cooling fan and condenser fan motors.

The cooling fan control interprets the PWM signal provided by the ECM as follows:

If a PWM signal of between approximately 12 % and 87 % is received by the cooling fan control unit , it will not power the cooling fans. If a PWM signal of 87 % or over is received by the cooling fan control unit, it will provide a feed to the cooling fan (C0005) and condenser fan motors (C0280) on SU wires. An earth path is provided for the cooling fan (C0005) and condenser fan motors (C0280) by the cooling fan control unit (C0701) on a pair of PS wires. If a PWM signal of less than 12 % is received by the cooling fan control unit, it assumes a fault has occurred and powers the cooling and condenser fan motors as described above. If a continuous voltage is received by the cooling fan control unit, it assumes a fault has occurred and powers the cooling and condenser fan motors as described above.

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 A/C system 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 A/C system to use recirculated air. The switch is mounted on the centre console, adjacent the A/C master switch, and is earthed (C0750) on a B wire.