Hiya - I have a 92 100S4 which uses essentially the same architecture as the V8 (they're al 44's after all!!). I had a similar problem. The car was OK when I parked it. When I came back to it the following morning the batery was flat (not enough juice to pull the starter in). I assumed that the battery had finally died as it had been previously layed up for 8 months although it had been OK for the best part of 3 months general usage. Jump started & drove to a local shop to buy a new battery & when I got back in the car I heard a strange thumping noise & a clattering relay. Upon further inspection the thump was the drivers window trying to close although it was already shut & the clattering was coming from the window control unit (drivers footwell). The window control unit had obviously been opened up before so I ad libbed & used a standard relay to give me power to the window system once the ignition is on. That was around 6 months ago & it has been fine since. I miss my total closure (hold the key in the lock position for 3 secs & it used to roll up all of the windows) & the delayed power cut off after the ignition is turned off but at least I won't get stuck with a flat battery again!!
