1999 540i electrical issue.
I have a 1999 540i with a 6 speed manual. Ive been having electric issues. The car will randomly not start due to the battery being drained by something. The car drives just fine, with no warning lights on. However the cars alarm will randomly go off and then stop after 2 or 3 minutes. The car will lock itself when i shut the trunk. The alarm will also go off when unlocking the car every now an then when using the key fob, and also alway when using my spare key for the first time after using the original key. The car will also randomly lock whenever i turn the car off. Im assuming there is something in the locking system that is causing the battery to drain. The car will sometimes be find for weeks at a time and then one day just be dead in a parking lot. and sometimes it will happen multiple times in a week. The battery is brand new and i have replaced it a few times just incase. I have taken it to my trusted workshop many times and they can not find the issue. They left it on a monitor for a week and the saw no battery draw. They even drove the car around alittle to see if they could trip it. Nothing. Does anyone have any ideas?
Thanks so much.