My AR 2001 , aux cooling fan rum at high speed all the time , it sounds like a 747 lol..
Anybody ran into this before ??? It will stop as soon a press the eco button . and it will kick back when a turn the heat or ac no matter what temp, my control is at....
thanks Paul

 

Sounds like a relay or a temp sensor has gone bad.

 

I have exactly the same problem on my '01 A6 2.7T. Thanks for the suggestion. The Allroad is getting a bit on the loud side also.