LeftFrank

Aux fan continuously cycling on and off while engine is off.
Afraid it will run down my battery overnight.

This is a 2004 A6 3.0 quattro.
Could it be a sensor?
Which one and where would it be located?

Thanks!

LeftFrank

Bumping.
Any ideas anybody?
Please?

JAGMAJ

I've had problems with my auxillary fan control module that caused these symptoms while the car was running, but I haven't heard of this occurring while the car wasn't running. I would think that your problem is still related to the module, though. Maybe some of our experts can chime in.

LeftFrank

I dug around and found a solution that worked, and since no one here who read my post knew the answer, i thought I would post it here for anyone else who might need the information.

Since the problem was the auxiliary fan going on and off while the engine was shut down, and the coolant temperature gauge in the dash was always right in the middle after warm-up, this eliminated the radiator sensors as a source of the problem.

Apparently the main controller for the fan with the car off is a relay that is in the ECU box in the driver's side of the engine compartment. In my car, it was the relay labelled "219".

I opened the ECU box and pulled out the 219 relay. It did not look corroded or wet as I've read was the problem for others, but the spade connectors had some oxidation on them. So I took some sandpaper and cleaned these connectors until they were bright and shiny, cleaned off any sanding dust, and reinstalled the relay, making sure that is was seated correctly.

And voila, no more problem.

CrodA6

sweet.