Audi 100 Trip Odometer and a few other issues

[Einhorn Hofmann]

Noticed a few things while giving the 1990 Audi some post-winter attention.

1.) The trip odometer stopped working.  Speedometer works.  (Now that I
think about it, I need to check if the odometer also stopped working).
Years ago I had the "bobbing speedometer" problem and this was solved by
taking the instrument panel apart and made the fix with a soldering iron.
Does the trip odometer have a similar known issue, or is it strictly
mechanical?

2.) The automatic climate control has a diagnostic mode whereby you can use
it to display the result of many sensors, including cabin temperature and
coolant temperature at different locations.  One of the values that it can
display is the voltage.  Generally speaking, when in this mode, you can see
the battery voltage rise to about 13.5 when the car is being driven, and
drop as low as 10.8 if you turn on enough additional accessories.  It might
not be the most accurate reading, but its there, and nice to have.
Recently however when I engage this reading, it just displays 12.0 and
never changes.  In the past, its always changed quite often depending on
engine speed and accessory draw.

3.) Finally, one of the two licence plate lights was out but when I touched
it, it came on.  The bulb is good and firmly in place.  Would that be a
grounding issue if only one of the two bulbs is affected?


Other than these tiny gremlins, the beast continues to purr.  Its a
rewarding feeling to realize that she's made it to see another spring :-)

Best wishes, and thanks for any insights into these small problems!

MC