My 96 A6 2.6 avant ot appears the rad fan aint working as today it boiled, the fans will run ok when you switch the AC on, However when you dont the fans wont cut in............But what i cant work out is that the temp gauge still reads normal even thou its getting too hot. There are three wires on the fan switch anyone know which ones to connect to see if the switch is bust. Also is there a relay for the rad fans and if so where?

 

Since the car is overheating but the temp gauge isnt showing it, you may want to try replacing the coolant temp sensor. Its a pretty common failure, and i believe it is used as the fan switch for your aplication. Also since the fan comes on with the ac, the fan and relay are ok. That is unless there is a second fan relay. I dont think there is thou.