I have a 1986 535i and recently it wont start because the battery is dead, after having sat for about 12 hours. I have replaced the battery and checked the alternator to make sure it is producing enough power and everything seems fine but the car refuses to start after having sat for too long. Apparently something is draining the power while the car is off, but I have no idea why so any tips would be greatly appreciated.
Im not sure if this is relevant but while the car is off the clock next to the dash dimly lights the time, additionally the doors will not lock when using the rear/trunk lock.
Thanks again.