[Marius1585]

Hey All,

Have an 04 M3 with low miles (40k) that I’ve had for 7-ish years and recently I started noticing some unusual behavior.

Last winter (Nov) it failed to start a few times, but ran fine after bring jumped. Started and acted normal a few weeks and then got stashed away in garage for winter sleep.

Late February or early March, had to jump it again and eventually took it for unrelated service and shop called back saying my charging system isn’t working and that I need a new alternator.

Got a new alternator but still had an issue or two few weeks later. Replaced the battery and no issues starting since then.

EXCEPT - this week I noticed the interior dome light coming on while I’m driving - looks like a short/bad connection. Can’t tie it to bumps or anything that I notice happening consistently, but I’m certain it isn’t supposed to come on and off without button being pressed or door opened.

I think fuse 49 & 52 are relevant to check here, but curious if anyone can help point me to where I should check the wiring and how I could potentially locate the issue. Scared that the short may leave me stranded or may ruin a new battery.

Also not sure what all those fuses cover and if there’s a number of modules I should test/check and where to find them. Got a DMM and some knowledge, and would like to try to pinpoint it rather than paying a shop hourly to seek an electrical problem.

Thank you in advance.

[NB STIG]

It sounds like you have a bad door actuator. Most likely the driver’s side. When these go out, you start having strange issues like the ones you described. Good luck!

[Marius1585]

Originally Posted by NB STIG

It sounds like you have a bad door actuator. Most likely the driver’s side. When these go out, you start having strange issues like the ones you described. Good luck!

Thank you! Any insight on confirming it’s the actuator? Why do you think it’s driver side?

[NB STIG]

I had the same exact issue. My car was draining the battery overnight because the interior lights were going on and off during the night. For some reason this gets worse at night when is cold or raining. Don't ask me why.

During the day, when I was driving, the interior lights would go on and off as well. I did some research online I found the same exact symptoms and the cure was to replace the door actuator. The reason I say it is most likely the driver side, but I can't guarantee, is because this is the actuator that gets used the most. Most people who drive these cars use/drive them alone. This happened to be true in my case.

Starting with the driver's side was a 50/50 chance and luckily I was correct!

I hope this helps!