mel g

2001 audi TT CQ. 51,000Mi.

Jan 2006, developed non-stop cooling fan, well after radiator had cooled, and I had to disconnect battery to get them to stop. After troubleshooting, decided fan control module was defective, and a new one fixed it ($98)

April 2006: weather warms up, ac doesn't turn on, and testing showed the cooling fans at radiator also don't turn on. Both are controlled by the fan control module. I repeat the troubleshooting, leads to conclusion of defective fan control module (again? - but I double checked, and Vag-com and Bentley detailed troubleshooting confirms it.) So, purchased my third FC module (price up to $150,) plugged it in while car partly disassembled. (Since I cant get access to all the parts for testing without partial disassembly) . All worked well, including output testing via Vag com. Cool air from ac, and I see the cooling fans work. All fixed, so I thought.

Put it all back together: re install battery box, reassemble all clamps, etc.
But then: No ac and no cooling fans! How could this be? It worked fine just yesterday.

Very puzzled, and bothered, I already have had 3 FC modules.

So, again went thru all the Vag com, Bentley trouble shooting, and it points to fan control module... could I have 3 defective modules in 3 months?
Impossible. But I saw fan and ac work just yesterday.

My son suggest rip apart the 2nd fc module and see if anything there shows up. I am out of ideas, and I certainly am reluctant to buy a fourth module.

I cannot believe what I found there: the screws that hold it to the chassis- same screws that I originally removed when I took off the original module, have penetrated the case of the module, and severely bent the PC circuit board inside!
This explains why the 3rd module worked fine while loose, but failed after I screwed it in place.

Moral of the story: if you replace your FC module, there must have been some manufacturing change, so use shorter screws( 6mm, X 1.0)

Rocky-in-Connecticut

weird.

coasTTal

Thanks, I bet the dealer tech could not figure this one out either.

the Quiet sTTorm...

Thanks, as fan 1 is out on Baby boy. I'll have to tackle this later this summer.

mel g

If only one is inoperative, the defect must be in that fan,not the module.

Fan Control module, and thermoswitches on radiator, can run both fans at low speed, or both fans at high speed.

the Quiet sTTorm...

which means then the whole fan is out.