I have a 2000 Audi A6 Avant Quattro that I recently purchased. I am having issues with the Auxiliary cooling fan. It is coming on right after starting the car, even though it is cold out and the AC is not running. It is running on high, sounds like a jet when on and when I stop the car, the fan drops to low speed but continues to run for several minutes after the car is off. I don't know why the fan is coming on in the cold weather, my understanding is that it supposed to come on when the AC is running and engine is running hot. I did recently replace the engine coolant temperature sensor to adress cold starting issues. I searched the forums and found some complaints about the fan not coming on, but I have a different situation here and was hoping for some input on how to diagnose the problem.

 

There is another temperature sensor that activates the fan. It is located on the lower coolant hose next to the radiator on the passenger side. Try replacing it and see if it solves your issue.

 

my fan only turns off when you disconnect the battery. Is this a sensor and if so how bad is it to change. I have basically no tools