Neither fan is working on my 96 2.8l A6. I searched the forums for similar problems and so far this is what I have checked.
1. Fan temp switch on the radiator (when the motor was hot i had continunity on all 3 terminals). Measured 12v on 2 of the 3 terminals of the connector and jumpering to the 3rd did nothing.
2. checked the 2 fan relays in the plenum box. pulled them out and hooked up 12v to each coil (to make it switch) and had continunity on the other terminals. They seem fine.
3. I noticed that the scockets for the relays had 12v on the terminals that fire the coils, but the terminals that get switched thru the relay did not have 12v on any side of the switched terminals (#30 and #87). I might be looking in the wrong direction but i think there should be 12v on one of those terminals.
4. I looked under the drivers side dash/knee board area and found more 6 more relays, but none of them were labled for the fans.
5. Checked the fuse panel and did not find any problem there.
6. Cut the wires to the fan and put 12v from a seperate battery and it worked.
Could there possibly be a fuse somewhere that I'm missing? It seems like i'm not getting 12v to the relays in step 3.
Any thought?
Thanks

 

Has it thrown any codes? checked your temp sensor?

 

The temperature gauge seems to be ok. starting from cold the needle moves to a normal position as the engine warms up, so i'm quessing the sensor is working. my a/c unit can double as a diaognostic display and is showing the folowing DTC codes.
"15.3 - Air Flow Flap Motor Potentiometer, sporadic open" and "22.3 A/C Refrigerant High Pressure Switch, sporadic open" and I'm not sure what they mean or if they are part of the problem. The a/c blows cold air too.

 

Those codes are for the climate control...

Anyways, somewhere between the fan relays ans the fans themselves there is an open (as you know). I dont have the diagram so cant point you to where its at, but this problem and the climate control ones point me to either a loose connector or open wires, prolly due to them rubbing metal. Find the power wire at the fans and follow them back. Found a 'bad' fuel pump and 'bad' transmission this way, both actually due to broken wires.

Second possibility is a fuseable link somewhere in line.

 

heres the wiring diagram

lets try this again.. PDF due to size

Attachment 3140

 

fixed

 

You can go to bentleypublishers.com for the repair manual that will have a wiring diagram in it. I would start chasing the wires back as far as you can looking for damage like midniteoyl said. You will only make it so far though you need to look for power from the relay down until you find the break.

 

Thanks.
I will look around for a broken wire or a fuseable link. The only power at the relays is for the coil only. There is no power on either termanials that would switch the 12 volts to the fans. where ever the power TO the relays is coming from must be missing. Gotta dig some more.
***
Edit. Went tracing back wires at the engine plenum relay box today. (Audi is real good at using color coded wires) It finally led me to another fuse and relay box, located behind the kick panel on the drives side. Inside were 4 more relays and 1 big ars 60 amp fuse that was labled 'radiator fan' and it was blown. I replaced the fuse and the fans came back! Thanks to all for the input.
After messing with this for a few hours I'm going to search on 'fuse and relay locations'.

 

I've been having the same problem.. My Aux radiator fan isn't coming on. I checked the fan, it works with 12V directly to it. upon getting under the dash to check the relay I found a 30amp fuse that was blown. I changed it and the fan started working perfectly for about 5 minutes then it blew again.

Any ideas what could be causing the fuse to blow?

Thanks in advance,
Chris

 

-That fan is pulling too much current

-Theres a short

get the .zip and trace it.