vol2650

I have an 04 B6 3.0 with a cooling fan problem. I am getting an P1931 error code relating to FCM and the only fan that comes on is the drivers side when AC is engaged and the AC blows hot. I direct wired the passenger side fan and it does come on, but only then. So the fans are working, but not normally. Tried doing the VCDS test under cooling module and they did not turn on that way either. Question is it the FCM or the relay? If it was the relay, wouldn't neither fan work?

John535is

The FCM is an expensive part, before you jump in buying another one have you checked the fan switch in the bottom radiator hose ( I have the 1.8 but assume the 3.0 is similar). You can replace the switch without emptying the coolant. If you keep the reservoir tank cap on tight, when you remove the switch (looks like a grey version of the green temperature switch on the engine) but this is only 2 pin version. You don't need any special tools, it just has a big clip. make sure you get a new rubber 'O' ring.

jukkapukka

I have a similar problem with my 2004 A4 B6 1.8T. Neither fans came on, even with AC on. I unhooked the FCM and put 12v to both fans. The smaller one on the passengers side came on but the main one didn't. Checked the resistance of both fans, and the main one was high (like 5k ohm). My guess is that the main fan failed and burned the FCM as well. Ordered new FCM and fan on eBay, and I'm going to attempt to change them out tomorrow. It would be great if I could do this without having to take the bumper off.