Tech Article Title Author Date
Fan Control Module Replacement RMcQ 2005

As many of you know I am flying solo with my allroad completely devoid of any factory or aftermarket warranty. At approx 60K miles I hit the first bump in the road. This is something that you should all keep your eyes out for since I found out later that the A6 guys are seeing this more that one would like.

The problem is that there is a rubber sealing strip that is part of the fan shroud of electric fan behind the radiator. This rubber strip can come loose and jamb itself in the fan blades. With the fan stuck the circuit is designed in such a way that rather than blow a fuse the car protects the fuses with a $218 fan control module. Huh?!?

Anyway, the symptom that lead me to check for this is a much louder than normal electric fan noise whenever the HVAC was on without the "econ" button pushed. What the car is doing is putting the other electric fan in front of the radiator into hyper mode. It sounded almost like the car was turbine powered or something. When shutting off the engine the fan would spool down for a few seconds after the engine was completely stopped. It was annoying, but the car did not overheat or have any other difficulty.

If you have a really loud electric fan all the time take a look and see if the fan on back of the radiator is spinning. If it isn't, look for the rubber strip:

Another look after I pulled it out a bit with my fingers:

When I got it out it looked like this:

So the next step was to be sure that the fan motor itself was OK. I did this by applying 12V directly to the 2 pin connector for the far which is located on the drivers side behind the headlight housing. You can trace the wire from the fan back to the plug show below.

You can see that I have a couple aligator clips attached which I touched to the battery. The fan ran fine so I knew that the motor itself was OK.

Next, I needed to make sure that the fan control module was indeed fried and in need of replacement. This can be checked by jumping pins in the "coolant fan control thermal switch" AKA temperature sender in the lower radiator hose on passenger side.

If you look closely at the above picture you can see the harness is unplugged. The connector looks like this:

To check the health of the Fan Control Module you simply jump pins 1 and 2 and turn the ignition on. You should get front and rear electric fan on low speed. I got nothing. Next jump pins 3 and 4 to simulate high coolant temperature. You should get both electric fans on high speed. Again I got nothing.

So I have verified that the fan control module is bad. The dealer price is $218 for part 8D0 959 501D. I bought mine for $180.22 at

So on to actually replacing the faulty part. Unfortunately I did not take many more good pictures, but the Fan Control Module is secured to the underside of the unit-body frame on the drivers side about 8" above the oil filter. It is not very easy to access this area and it is also difficult to route the wiring through some small spaces.

Here is a pic of the old and new unit side by side so you know what you are looking for:

The long wires that come with the module go up through and connect back behind the headlight where we were already working earlier when testing the system:

The other connection on the module will plug right in when you unplug to old one. It is really a pain to get it in there. It would have been easier with the oil filter removed so if I had it to do again I would have waited for my next scheduled oil change to do this.

I jumped the pins as above once I had the new module in and high and low speed worked as expected. So that's it. My first out of warranty repair cost me $180 at 60K miles.

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