back-up lights not working on 95 A6q

[feb@febsun.cmhnet.org]

Well, sometimes working.

I found out this week the tail lights on my 95 A6q (automatic) are
working only sporadically.  For some time now I've known
that the tilt down outside passenger side mirror was sometimes
not tilting down, and sometimes tilting down only several long
seconds after the transmission had gone into Reverse.

Until this week, it never occured to me to check the backup lights
to see if they worked too.  Turns out they're not working either.
The gear indicator on the dash (PRND321) works fine and perfectly.

So, I pored through the Bentley to see how things were wired.
Bentley shows a multi function transmission range (TR) switch mounted
on the tranny, and one wire from this TR switch goes to a relay under
the dash which runs the backup light and tells the mirror controller
that the car is in reverse.  (This relay is actually one-half of
the Park and Neutral Position relay module.)  When the tranny is
in Reverse, the TR switch is supposed to ground the coil of the
relay. 
   (TR switch -- family album A6Q-95-927-50-31, pn 4A0 919 821.)
   (relay -- family album A6Q-95-937-34, pn 4A0 951 253 ??, not too sure
    about this one - family album doesn't identify the exact function of
    the relay, but does say "for automatic".)

The TR switch is under the left side transmission mount, according
to the Bentley.  Under the hood, I can see the mount, but I can't
see anything under it.  I have not tried, yet, to get under the
car to see if I can see it any better.  The procedure in the Bentley
for replacing and adjusting the switch starts with removing the
left transmission mount...

I pulled the relay out from under the dash and stuck an ohmmeter in
there to measure continuity between the output of the TR switch
and ground.  With the tranny in Park, N, D, 3, 2, or 1, I get open
circuit.  With the tranny in Reverse, I get about 800 ohms
between the switch output and ground.
For a ground reference, I tried a metal support under the dash, and
also tried the cigarette lighter surround.

800 ohms sounds like an awfully high resitance for a switch that's
supposed to be shunting a relay to ground.
The relay coil resistance measures about 80 ohms.


Anybody experience a problem this sort on the 4 speed automatic?
Do I really have to change the TR switch on the tranny?
Any chance it's just the relay?

Franco

--
Franco Barber                   feb@febsun.cmhnet.org
95 A6Q w/Gamma CD mit RDS!      Columbus, Ohio  USA