1980 528i Door Locks

Ernie in Houston · Post by **Ernie in Houston** » Thu Jun 30, 2011 12:25 am

I've got question I'm hoping someone can aim me in the right direction on. I've got a 1980 528i and the auto door locks stopped working and are in the locked position. No big deal for the most part, since I can open all the doors manually, but it also means the fuel filler door is locked and to open it I have to go into the trunk and manually pull the leve back to release the door.

Anybody have any ideas where to start looking for the possible cause. I've checked the fuse (No. 5 from what I can find) and it seems fine.

Any help would be greatly appreciated.

Thanks,
Ernie in Houston
'80 528i Auto (Brasilbraun Metalik)

Keith · Post by **Keith** » Thu Jun 30, 2011 2:20 am

It's likely the master switch mechanism in the driver door. When the position of the driver lock changes, it sends voltage to all the other locks to change position as well. If this is not working correctly, the whole system will not work. Pull your inner panel off on one of the other doors, and plug a voltmeter into the plug that goes into the lock mechanism. Then have someone move the driver lock either up or down with the driver door closed. You should get a voltage reading on the plug in the other door. If not, you probably have a bad master switch, which will probably need to be replaced. My was actually melted, probably as a result of moisture and electricity being combined. You could also check for voltage going into the master switch itself. If none, then you probably have an issue further down the line.
If you are getting voltage to the other locks (which i doubt), sometime gummed up mechanisms can cause the locks to hang up. Cleaning them with brake fluid, and lubing with lithium grease can help.
Let me know what you find. I just sorted mine out a few months ago, so I should be able to help.

Ernie in Houston · Post by **Ernie in Houston** » Thu Jun 30, 2011 2:06 pm

Thanks Keith....I replaced the motor in the drivers door about a year or so ago with a used unit. As you said, my old one was pretty much fried. After I replace it, everything worked fine for a while, then became intermittent, and then finally stopped.

I'll take a look at the motors like you said, and will let you know what I find out. Thanks for the reply and insight....I appreciate your help.

Ernie