how to: diagnose and fix faulty fans on a U12

[rathies]

Just recently I had some trouble with my u12 fans not working, Another member also asked me about this. So i worked out how to fix mine and thought i would post it up on here for future reference.
you might notice your fans are faulty when the engine temperature rises above normal operating temperature when you are moving.
Your fans might also only operate at one speed and not alternate between high and low as required.

First step is to check the fans are able to move freely while the engine is off, move them with your hands and make sure the motors aren't jamming up or there is nothing in the way. Mine were bent into due to the turbo set up and this caused other problems which i'm about to get to.

second of all start the car, try switching the air-con on, this should make the fans come on low speed. if not proceed to the engine bay and unplug the red connector circled. normally you would notice a change in engine speed and the fans should blast on high.

If they do blast on high then your temperature sensor is faulty. If they dont but the engine speed changes as you plug it in and pull it out then your relays are fried. If the fans come on low then one of the relays is dead and not both.


This relay box is located on the left hand side of your engine bay, the 2 circled in green are the relays for the fans, the one on the left is for low speed and the one on the right is for high speed.
you can check quickly if they are burnt out by swapping the one circled in blue (its for the air-conditioning) into the low speed socket. Pulling the red plug off the temperature sensor should make the fans come on low speed, if so you need to goto a wrecker and obtain these items from a wreck.

My relays died due to an obstruction in the fans causing them to stop moving. Since there is no fuse on the circuit as far as i'm aware. If this doesn't fix your fans then I would suggest either faulty wiring or broken motors.

[rathies]

I should also mention that to get the relays out of the socket you need to lever a flat screwdriver under the tab.
If your fans are constantly on high even when first starting the car chances are the red coolant temperature sensor plug is either loose or has dirt in the connections. Try unlplugging and spraying it with contact or carby cleaner. Pushing the plug back on should make the fans go back to normal.

[Jono]

I believe the fan circuit is fused through one of the fusible links in the black box on the battery side of your engine bay. They are quite high current fuses. Your fans were probably drawing heaps of power through the relays which will burn them out quite quickly.

[rathies]

yeh i had a feeling they were fused there. Well that answers that question. Mine werent blown but definately worth a look.