AS said on:
http://forums.vwvortex.com/zerothread?id=2983133
Is it certain fan speeds that don't work or just nothing at all? The relay for the blower is on the top row of relays in the fuse panel furthest to the left. Both it and the the speed selector dial get really hot during operation and over time that heat cooks the connections, it's a known issue in all B3/B4 and later interior Corrado's. Basically when it happens you need to replace the HVAC controls and/or relay, there's no really effective fix to the problem. The relay is alot cheaper than the controls obviously so to test just drop the fuse panel cover, put your hand on the relay and turn the blow on with the switch. If you feel the relay click open then it's more likely to be the controls. If you don't, replace relay and begin troubleshooting again.
N.B. This relay position is for the B3 and may be different on the B4.
BUT - I have the same problem and not yet tried it... I HAVE dismantled the console & the heater control looks OK. THE FAN looks like a nightmeigh to get to and replace.
Raphael Lytton, December 2006
