Question Hello, please can you help.
1998 BMW 318i started with fault on central locking, on one door and battery going flat within hours.
disconnected wires in that door and taped ends securely. still shorting out overnight.
Pulled fuse for central locking and elec. windows.
Still shorting overnight.
Number 37 fuse,(rt. side tail/no. plte.light/dashboard light/ headlamp beam adj.). Whole fuse (10amp),Actually melts.
unable to track problem, left Fuse 37 out.
Now none of that circuit working, (as expected), but battery still draining overnight.
Battery ok, but purchased a new one anyway.
Still shorting out overnight.
Removed fuse 25, (common to some of the Fuse 37 circuits.
Stopped shorting out.
But have no sidelights or tail lights etc. But only way I can use the car.
I hope that is clear
Regards
Answer Welcome to electrical troubleshooting a BMW.
Not sure on the 318, but the 1998 7 series have a "sleep mode" in the electronics. Basically, after a fixed amount of time (Google it....I think it was 17 minutes), the computers quit talking to each other, and the current draw drops to almost nothing. If it doesn't, or if something is "waking it up", then the battery will drain overnight.
Had this on a '96 740. Wound up being a bad socket in the door light.
Put a multimeter in line with your battery and watch it to see if it enters this sleep mode, and/or comes out of it on it's own.
