Hi, my name is Ed, newbie here on Audiforum, owner of a 1992 100 CS Quattro for 8 years and love my car.

My case is that after having tried to jumpstart my car last week, I ended up frying something when I hooked up with the cables inverted (product of almost 48 hrs no sleep, first time this crap happens in my 35 years of driving and limited mechanic tinkering). My mechanic says it's the "body control module" (but I'm suspicious). Basically, the only thing wrong with the car at this point is that the climate control is out (no a/c or heating), the power window controls are out (can't roll windows down), interior lights seem not to be working and a few other minor issues that may or may not be related to the major issue (fried bcm or ccm?). A fuse may have also blown (have not checked since Friday), since the clock and interior lights were working and now they don't.

The car got a new alternator and battery (battery died last week after a good 8 years service without ever checking it) and it is running smoothly. Relay B3 / A12, which I understand is the one that has to do with the "comfort controls" is not plugged in, but car still runs smooth. If I put in the relay, the engine runs but I feel an intermittent power failure. Like when you have a damp distributor.

Now, does this car have a comfort control module such as other later C4/A6 models thru 1997 and even later (part no. 4B0 962 258 C)?

All wiring from the B3 relay looks good. I looked around under glove compartment (taking black plastic protector shield out) and side panel of passenger side footwell and did not find any thing that looked like a bcm or ccm.

Please help!

Ed