Electrical gremlins (elves?)

[Chris Newbold <newbold@telerama.com>]

Looks like the Audi Santa, er God, of electricity has come early this
year... I've got some weirdness with things driven off the driver's door
jam switch.

As in most Audis, the driver's door jam switch drives a number of things:
  o dome light
  o radio on binger
  o lights on binger
  o alarm
  o interrupt power windows (first time door is opened after ignition
    switched off)

In the last few days, things haven't worked right; at first I figured
that the switch must be worn or corroded. However, I've noticed that
the failures affect a random collection of the items above.

Tonight, for example, the dome light did not go on when I opened the
door, but the lights-on and radio-on binger worked, and so did the
power-window interrupt. This morning, I had dome lights, but no
binger.

I've also noticed that the seatbelt binger is flakey; if you start
the engine without the driver's seatbelt buckled, you're supposed to
get the red idiot light and binger for ~15sec. However, I usually
get one or the other, maybe neither.

Any ideas? At first I'd suspected the door switch, like I said. That
doesn't account for all of it, especially the seatbelt binger. I also
suspected the binger itself (bad connection in instrument cluster),
but that doesn't explain the dome light behavior. Bad ground? But where?

Any thoughts on where to begin from the reigning Audi electrical
exorcists would be appriciated...

-Chris
1993 90CS 5spd 71k miles