Shocking Electrical Issus

[Kai]

Ok, sorry for the corny title. Monday I slowed down to pick a guy from my class up and drive him to his car so he wouldn't have to walk through the freezing rain. As I start to pull away my interior lights all come on, the emergency flashers come on, and my door lock activate. Strange. I get back to the dorm, go rest for 45 minutes, come back down and my interior lights ( I don't know if the doors were unlocked or not, I pushed the unlock button before I got close enough), when I pushed the button the alarm goes off, wont stop with the button since the fob isn't working at its best right now, so i put the key in the door and finally get it to shut up. The flashers go off once more that day, end of problems. Yesterday, come back after I locked the doors to find doors unlocked, interior lights on, try to open the door, alarm. Today, on my way to class flashers go off, interior lights on, locks activate. Hmmm. I drive down after class to the closest high school where I am doing chemistry demos, get down in there and come out to my car...doors are unlocked, lights on, open door, alarm. These days have been cold and rainy, so that might be a contributor to the problem arising now. I assume the security system isn't messing up since the alarm doesn't go off unless the doors are opened, which means it is doing its job because the system is on, but for some reason the doors unlock. Thoughts.

[MADDOUG]

Sounds like the live to the alarm is getting interrupted either a dodgy battery or a bad connection.

Most alarm systems after having battery disconnected will unlock the car doors on re connection,this may explain why the doors are unlocked.

The alarm though will still be on when power returns but the doors will be unlocked.

Check for loose fuses and if the alarm live connection comes from the ignition barrel then suspect the barrel electrical connection are worn inside.

I have had this scenario on a car I had that had an anti hijack/valet mode and all sorts of tricks up its sleeve,the car could be heard often at night to beep twice as the system came back on,eventually the alarm would often go off without the car being touched.Battery going bad was the cause of mine,the voltage was up and down and the alarm detected it as voltage drop similar to a door being opened and the interior light coming on etc,although not the full voltage of powering an interior light the drop was within the scope of the alarms parameters so it was noticed

A dodgy door switch with a helping off water will trigger the alarm but yours unlocks the doors so main live feed to alarm is the cause.

Check the earth connections as well.

[bmwbmc]

just curios what was it in the end? i would have guessed ignition switch?

[Kai]

It hasn't been very rainy again so I don't know if it even happens anymore.

[bmwbmc]

yep,i have heard of water playing tricks on the electrics of the e39