Odd gauge problem [E30]

[Spiegelthal.Dave@xxxxxxxxxxx]

I've got a '91 318i with a vexing instrument panel problem, and  I'm fishing for
ideas from the clever folks on the Digest here.
     My odometer recently stopped working because of broken teeth on two of the
gears that drive the mechanism in the speedo/odo head (Motometer brand).  I
ordered a used complete gauge cluster from Bimmerworld in Radford, VA (very
reasonable at $80), and I took the gears I needed from it and put them into my
speedo head.  So far, so good.  But upon reinstalling the cluster in my car:
(a) The odometer still doesn't work;
(b) The speedometer now is reading about 15% low; and
(c) The tachometer doesn't work either (completely dead).
For what it's worth, the idiot lights, panel lighting, and gas and temp gauges
still work fine as before.
      I tried connecting the tachometer from the used cluster I bought into my
car and running it up, but it didn't work.  My three manuals (two Haynes and a
Chilton) don't have any wiring diagrams that show details of the instrument
panel wiring.  Since (apparently) the speedo/odo and tachometer get their inputs
from two separate electrical multi-pin connectors (one blue and one yellow, if I
recall), then they should operate completely independently, shouldn't they?  The
only thing I could think of is that maybe they're VERY sensitive to
electrostatic discharge, and somehow, in removing them and moving them around, I
managed to shock the electronics to death.  However, this theory wouldn't
explain why the tach in the used cluster didn't work when connected up (unless I
killed it with static also).  I can't believe these instruments would be THAT
sensitive to static electricity, but I guess it's possible.
     Does anyone have a similar experience to talk about, or a good theory?  It
would also help if anyone could recommend a shop in the Northern
Virginia/DC/suburban Maryland area that does good electrical work on BMWs. Many
thanks in advance.
     Dave Spiegelthal  '91 318i (E30/M42)
     Calverton, VA

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