Cooling Fan Description

Cooling Fan Description

The cooling fan is located on brackets forward of the radiator. The fan motor is operated by a cooling fan relay controlled by the Engine Control Module (ECM). The main relay supplies a feed to the coil of the cooling fan relay. A permanent feed is supplied to the coils of the main and cooling fan relays located in the engine compartment fusebox. On V8 models a coolant temperature sensor is located in the inlet manifold on Td5 models the sensor is located in the outlet housing.

The ECM controls the operation of the main and cooling fan relays. At a preset temperature the ECM receives an input from a coolant temperature sensor above the values stored in the ECM. The ECM logic enables the earth path for the coil of the cooling fan relay. The fan motor then gets a feed from the closed contacts of the cooling fan relay.

When the engine temperature falls, the sensor gives an input below the values stored in the ECM. When the input from the coolant temperature sensor is low, the ECM interrupts the earth path to the coil of the cooling fan relay. The contacts of the cooling fan relay open, this action breaks the feed to the cooling fan motor, and the motor stops. The cycle will start again when the engine coolant temperature rises and the sensor sends a high input to the ECM.

The ECM has an engine off function, when the ignition is turned off the ECM logic goes into a watchdog routine and monitors the coolant temperature for approximately seven to ten seconds. If the coolant temperature is still high, over 100°C (212°F) - V8, 110°C(230°F) - Td5, the ECM logic can control the operation of the fan motor.

On V8 engines the ECM will only enable the fan if the inlet air temperature is over 60°C (140°F). The ECM will allow the fan to run for a maximum of ten minutes however the ECM continues to monitor the coolant temperature. The ECM logic will stop the fan if the coolant temperature is below the acceptable values stored in the ECM. To prevent a flat battery, the fan will be stopped (regardless of coolant temperature) if the battery voltage falls to 12 V.

Cooling Fan Supply

Circuit Supply

A permanent feed from the battery positive terminal is connected by an R wire to the engine compartment fusebox. A feed from this wire is connected to the contacts of the main relay and also to fuse 13. The feed passes through fuse 13 and to the inertia switch on a NB wire The feed from the inertia switch flows on a WG wire to the engine compartment fusebox and is connected to the coils of the main relay in this condition the coil and contacts of the main relay receive a permanent supply.

The permanent feed from the battery on a R wire to the engine compartment fusebox is also connected via fusible link 1 to fuse 5. From fuse 5 the permanent feed is connected to the contacts on the cooling fan relay. In this condition the contacts of the fan relay receives a permanent feed from the battery via fuse 5.

Main Relay - Ignition Supply

When the ignition switch is a position II, the ECM switches on the earth path for coil of the main relay. Current flows through the coil of the main relay and flows on a UR wire to pin C0635-23 V8/C0658-21 Td5 on the ECM With the coil of the main relay energised the main relay contacts close, power is now available to the coil of the cooling fan relay, via the closed contacts of the main relay.