Door lock actuator motor

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Door lock actuator motor

Post by dsw99a »

I went for my weekly "warm-up" start(78 530i). All good -starts fine. did nothing, except opened and closed the sunroof and sprayed a bit of lube on the cables. While the car is warming up

Came back about two minutes later and saw smoke. I thought no biggie - exhaust or something burning off, although it did have that plastic/wire burning smell to it.
Finally realized smoke coming from the door, through the opening for mirror adjustment! And the door card was really warm. I immediately freaked, ive heard/read stories where a car catches on fire, and burns the whole house down. Car is outside under a patio extension 8' from the house :shock:

I have a battery cutoff switch and quickly cut power. and sprayed some simple green in there, didnt want to use water. I did kinda freak.
Franticly grabbing screwdrivers to get to the inside of the door, still a little smoke coming off. Got the door card off. I can see a burn mark on the metal, thought it was window motor, but it is the door actuator lock switch/motor. I cant even lift or push down the lock knob, must be burnt out/up?

I checked the fuses. nothing of them burned out. the location of the specific fuse for this item is not listed on my fusebox cover? all the wires are fine, none burned, Luckily! I figured it would at least be a rewire job.


Im guessing its toast :lol: (pun intended)

anybody heard of this?
maybe more importantly anybody have one for sale?

another note; i could lock the lock with key, the lock system never quite work correctly, i really dont have to use it, hench, i never bothered with it.

can i just omit?



Last edited by dsw99a on Mon Jun 13, 2022 3:52 pm, edited 2 times in total.
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Mike W.
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Re: Door lock actuator motor

Post by Mike W. »

Wow, I've never seen that before. :shock: FWIW, the drivers side is actually a control unit, not a motor. Simplifying a bit, it's a big transistor with a couple of switches inside, but it looks like the others which are motors. I did have a control unit die one time when I was missing the window seals and a bunch of water got in, but nothing so dramatic as yours, mine just died a silent death. Assuming everything else is ok, the motors, all 5, and the wiring, you "should" be able to resuscitate the system. But as you hinted the original design seems flawed, the clutch override is so weak it often won't unlock. Usually lock, but more often not unlock.

I'd planned on using E28 parts on my last E12 as I'd harvested it all from a parts car one time, but it would have to be everything. E12 locks are a bit odd as they are 3 wire with a dedicated ground and supply power to either lock or unlock wire instead of reversing polarity like every other actuator I've found, and I did research them thinking I could just throw in different motors and all would be well. Not that simple I found out. I was looking at either a crapload of relays or an entirely new system, which would have been much easier given what you can find on Amazon these days. I mean they've got one for under thirty bucks. Two remotes, 4 lock motors, wiring and a control unit. Probably won't last 30 years, but at that price? Wouldn't include trunk or gas door, which could either be worked around, with some work, or ignored. You could, but shouldn't have to run new wiring.
Mike W.

1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
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Re: Door lock actuator motor

Post by 528i-1981 »

Lock upgraded his central locking system in his '79 to a modern one with a key fob. I don't know the details/components, but he's a crafty guy.

This is really something, and a reminder to install a battery cutout.
(oo=00=oo) Eric
1981 528i Manual
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