[200q20v] great gobs of green--ABS switch repair

[Phil Rose]

One of the few electrical quirks in our new-to-us '91 200q was that
the dashboard's ABS switch did not function. The "ABS-off" indicator
bulb in the IC was working, and ABS did activate/inactivate as
expected using the  diff lock switch on the console--but no ABS light
via the dash switch. So today, armed with a can of DeOxit, Q-tips and
an hour of spare time, I had a go at the switch.

The whole assembly pushes out from the rear (radio removed), and then
the switch is easily separated from its rear connector. Once settled
inside under a good light, the first thing I saw was a small amount
of green stain on many of the 7 or 8 contacts at the rear of the
switch. I cleaned these with DeOxit, and the green came off, but it
didn't seem to me that it was just a matter of ordinary corrosion
(i.e., brass oxidation). I tested the switch back in the car and
found that this cleaning did not affect the problem at all. Nada.

So...went back in the house, and now I decided to take apart the
switch to get at the innards. This was done by carefully prying up
under _both_ sides of the switch housing with a couple of small, thin
screwdriver blades (jeweler's screwdrivers). Inside are four sets of
sliding contacts (4 pairs of sliders--having contacts on opposite
sides). These contacts were completely gunked up with great gobs of
the same dark-green stuff that had evidently oozed out onto the
external contacts. Except that inside there was _really_ a lot of
this crap. Since the switch housing is a dark green plastic, I
surmise that the white lubricating grease (an excessive amount!)
found inside the switch had reacted with the plastic and this
combination was covering everything!

I spent about 30 minutes and 9 Q-tips applying  DeOxit and wiping
away green stuff. It cleaned off easily, although getting at it with
Q-tips was a bit tedeous. When everything looked reasonably clean
(it's hard to get it really clean since space is limited) I installed
the switch, and now--voila-- it works perfectly for the first time
since I've owned the car. Small victory.

Now the remaining problem is the left (rear) window operation (lack
of), which I hope is also merely a dirty switch contact. The car
doesn't have enough miles to make me expect a broken wire in that fat
bundle coming through the door (famous last words).

Phil
--

Phil Rose				Rochester, NY
'91 200q	(130 Kmiles, Lago blue)
'91 200q   (57 Kmiles, Tornado red)
	mailto:pjrose at frontiernet.net