Auxiliary Fan comes on and won't turn off
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.