RE: 87 5KCSTQ instrumentation light problem

["Paul Meyers" <paulm@viewsoft.com>]

I actually had the whole clock/computer rocker switch, etc. module apart to
troubleshoot the autotest check switch (cleaned contacts) and rebuild the
computer control rocker (bad contacts on the reset function). Somehow I blew
out some of the lights, both on the rocker switch and the clock. A trip to
radio shack (and some soldering) and the Audi dealer (plug-in
instrumentation lights) later, I have a completely functioning clock module
and the reset switch works to mister computer. While I had it apart, I
tested the pot all the way to the connector (including the flexible circuit
board). It measured a smooth 0-10k ohms, with no noise or glitches.
Interesting symptom: when the booster works, the dimmer works nominally.
When the booster fails, the working lights (instrument cluster, clock module
fail to dim. I exercise the pot by itself, but it turns freely with no trace
of rubbing or grittiness.

Other ideas?
-----Original Message-----
From:	Scott Mockry [mailto:scottmo@teleport.com]
Sent:	Monday, June 07, 1999 12:09 PM
To:	paulm@viewsoft.com
Subject:	Re: 87 5KCSTQ instrumentation light problem

Paul,

Have you checked the rheostat (3 terminal potentiometer) that controls the
brightness level, which is located in the clock module next to the center
air vents? This clock module/rheostat assembly, has a flex circuit on the
back which may have some connection problems. It looks like terminal 4/P2
on the light control booster module, should receive a varying voltage from
the rheostat.

I have never heard of any problems with these light control booster modules
before and it seems odd that the replacement module has the same problem.

I have one of these lighting control booster modules that I just removed
from a 1987 5000TQ that I am stripping down for a track car. If you find
out the replacement module is also bad, I can sell this module for $45

HTH
Scott Mockry

I have not yet done the dangle/rap test on it, but I am
>dismayed that perhaps many of the parts of this vintage have the same
>problem. I have heard that broken solder traces are endemic on older Audis.
>Is there hope of finding a good used module, or do I just need to (gulp)
>learn to live with the problem? Is there possibly a way to get a circuit
>diagram of this part, so I could trouble shoot it myself?
>
>Paul Meyers 87 5KCSTQ 130K miles