I brought home a new project on Sunday: a 1991 BMW 318is. I’ll post more on the car itself at some point in the future, but I thought I’d quickly document the first fix (of many, I’m sure). The power mirrors (standard on all E30s in the US, I think) didn’t work properly when I got the car. They’d move in only one direction, and not exactly in the direction the switch was pointed, either. Moments after buying a replacement switch from someone on r3vlimited.com I found a writeup with some very vague notes on removing the switch from the door and drowning it in WD40 until it worked properly. I thought I could do a little better!
The first step is to remove the switch from the door. I found this was easiest by popping the joystick hat off with a screwdriver (or use your fingers) and then using a screwdriver to gently finesse the switch mechanism out of the handle via the exposed holes. The switch is bigger than I expected. Once the switch is free from the door, pull the connector off the back (it’s keyed, so you don’t have to worry about labeling it).
Now go find a clean workspace where you can disassemble the switch. It contains four dumbbell-looking balls supported by four improbably small springs, all of which are just waiting for an opportunity to escape down your floor drain. Just use a small screwdriver to gently pry the outer black switch housing away from the translucent yellow backing on either end. Keep the switch oriented with the joystick facing straight down so that you don’t dump the balls out.
Once you’ve got everything apart, you’ll see something like this:
There was obviously some sort of dielectric grease on the back of the copper contacts which over time stopped inhibiting corrosion and corroded itself. I think we’ve found our culprit!
I swabbed some Tarn-X (purchased from Lowe’s for another project) onto the copper with a paper towel and kept rubbing until all of the green was gone. Then I finished it off with a vigorous rub with a green Scotch-Brite pad. I expect this will last about 20 minutes before starting to oxidize again, but it’ll do for now. Unbelievably, I failed to get an after shot of the contacts after cleaning them up.
Next I used more Tarn-X on the roller balls; you can see the kind of results I got with this side-by-side shot of a clean ball and a dirty ball (heh, heh):
Finally, I reassembled the joystick components:
If you have some dielectric grease, this would be the time to slather some on the piece with the connectors. Then just snap the two pieces back together. The back piece clips neatly back into place; there’s a key that aligns it with the joystick housing. Installation, as they say, is the reverse of removal. You should now be able to move your mirrors in all four directions!