hi all, I will ask the question first and then give some background, so if you don't want to plough through the dull stuff, you won't need to

I've got a 2006 B6 Passat 2.0 TDI Sport (140) and there are two fans on the radiator - a big one and a small one. Can anybody identify the purpose of each of these for me please?

The background is that I have a problem with my aircon - the fan blows fine but it doesn't get very cold. I had the AC recharged last year and it made a big difference. When this summer started it became obvious very quickly that I was once more suffering from a lack of cooling, so I headed back to the garage for a recharge and asked them to check the system for leaks. They reported that there was a minimal loss of refrigerant, well within what they would expect for a full year.

Whilst fiddling under the bonnet today, with the engine running, I noticed that there were two fans on the radiator. The big one was cutting in and out, which was what I expected it to do. The smaller one wasn't running at all.

A number of years ago I had a Rover 75 and it displayed similar symptoms - air con not cooling - there was a known fault with the 75 where the control module for the single radiator fan would fail and this stopped the fan turning, with the result that there was no aircon. I replaced the fan (which contained the module) and all was well.

I know that my model of Passat has a known problem with the air con compressor, but I'm hoping that the fix will be easier than this, and the smaller fan is linked with the aircon. I'm also hoping that a £3 part which takes six minutes to fix will do the trick, but then I'm an optimist

If anybody can confirm the function of the smaller fan and if it's failure will present the issue I have, I would be very grateful.

Many thanks

Richard