[spiderserie4]

do you recall if fuse #7 was blowing even with the heater fan switch turned off?
Did you hear the fan blowing away happily?

The fan could be seizing (quite common!), that would draw excessive power.

 

[spiderserie4]

yes, removing blower motor is one of those real PITA jobs! But, you can try putting 12v straight to the blower motor and see if it runs well, look just above your gas pedal, you will see the wiring connections there on the heater assy. itself.
dont know which ones you need to connect to though.......experiment a bit!
http://www.alfabb.com/bb/forums/348135-post6.html

 

[spiderserie4]

contact Papajam via pm and politely request one of his suitable for framing wiring diagrams it is worth its weight in gold

I don't think Jim (Papajam) has gotten round to a coloured S4 wiring diagram (yet).....he has the alfa b/w one on pdf which is very useful, though, but nothing like his own coloured transcriptions..........I'd even pay to have one of those for an S4!

 

[spiderserie4]

Did you manage to get the heater fan to turn with direct power?

I would in any case drop down the fuse box, turn it over and thoroughly check and clean with contact spray all the wiring connections there.