Cooling fans not turning off

Created: 07. 06. 2003
Updated: --. --. ----

Model: 306 (2 speed twin cooling fans, A/C)

VIN: 30 108 962 to 30 276 791. This is the chassis number range for the wiring diagram applicable for this particular vehicle.

Symptoms: The cooling fans keep running indefinitely after the ignition is switched off. The problem disappears for a period of time. Usually the fans ran until the battery went flat. It was also noted that the A/C system and rear screen demister was operable with the ignition off.


Possible Cause: Water in the cooling fan connector. This connector is located on the left side of the cooling fan unit and is accessible from the rear of the front panel. Nearby on the left chassis rail are 2 more connectors that should always be checked in the event of a cooling fan malfunction.
The picture on the left shows the connector from the front with the bumper bar removed. It can be accessed from the back, removal of the bumper bar is not required.

Diagnosis: The first item checked was the A/C main relay in the passenger compartment next to the fuse box. The relay was found to be energised with the ignition switched off. The relay coil is normaly supplied with 12V from the ignition switch via fuse number 5. The ignition switch tested ok, no short circuit to positiv between ignition switch and relay. We isolated the engine bay harness by disconnecting the main connector in the plenum chamber. The relay switched off after that.
On this paricular model, fuse number 5 supplies the hight speed fan relays, the control unit for the cooling fans, the compressor cut- off relay and the pressostat. The water inside the connector short circuited the ignition wire to battery +. This activated the cooling fan relays and also provided feed back to the A/C relay.


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