i have a 98 audi a4 quattro and the auxilliary fan is not turning on! When is it suppose to go on? and where does the Aux. Fan Control Unit located?

 

I'm assuming you mean the electric fan and it should come on when the coolant reaches a certain temp, assuming your talking about the one on the radiator. If thats the case it may have become unplugged(unlikely) or more likely the fans burnt out. The fan will need to be replaced in this case, or it could possibly be the temp sender unit but on the Audi I'm not too sure on placement of this but if thats the case the sender unit would need to be replaced.

 

does anyone know if the 98 4a quattro even uses the radiator fan control units?
and where is it located?

 

Cooling fan normally turns on when the thermostat is fully open (approx. 200 F).

Definitely check the coolant temp sensor.

Bench test the fan by removing the harness and feeding 12V to it (Take two pieces of long wire and touch one to the positive terminal on the battery and the other to one of the terminals on the fan where you just unplugged it. Use the other piece of wire for the negative/ground.) If the fan turns on, its good. If not, you need a new fan.

 

thanks

 

your auxiliary fan should turn on when your A/C is running my 2001 a4 has a electric and a motor driven fan so if every thing is working all right the mechanical fan cools the engine and the electric is for the A/C.
So turn on your A/C and it should work unless your A/C don't work.

 

FCM is located at the top,inside of the radiator, I got it replaced recently