A bit more trawling through the net and I am now wondering if the s4 has 2 fan modules. A guy with a 2005 s4 cab claimed to have the same issue as me, changed the fan module that sits in front of the condenser only to find that the aux fan module is attached to the underside of the n/s chassis leg. I know the b5's had one under there but didn't think the b6 did. As usual, the more you read posts and articles online, the more conflicting info you get! Only way to know for sure is pull the front off again at the weekend and have a look. As much as I like the S4, working on them and even seeing certain bits on the engine is just a nightmare without some serious dismantling, another reason that I feel its time to get rid of it. Its been fun and I always wanted one but after 10 years of ownership and many thousands spent, I've had enough lol