[Biturbos4] Review mirror upgrade

[Ti Kan]

Hi all,

The original auto-dim rearview mirror in my 2001.5 biturbo S4
stopped auto-dimming, so I looked into upgrading to the later style
Audi units with a built-in digital compass.  I found a tech article
on Audiworld about retrofitting the one with Audi part number
4Z7 857 511 01C:

	http://www.audiworld.com/tech/int36.shtml

Basically, this mirror was originally developed for the Allroad but
is compatible with a number of different Audi models.  After being
unsuccessful in locating one at reasonable cost (new one is deep in
the $500 range from the dealer, gulp), I started looking for a used
one.

Then, I came across an improved one that was found on the B6 S4, which
has part number 8E0 857 511 A 01C.  This one has a pushbutton switch
that allows the auto-dimming and the compass to be independently
turned on and off.  So, I bought it and proceeded to install it in my
car.

The procedure outlined in the Audiworld article above applies with
this mirror as well, so I won't elaborate.  The new mirror's plastic
wire cover did need to be trimmed about 1/2" shorter in order to
fit the B5, but it was an easy thing to do with a hack saw.  The
mounts are the same and the electricals are simply plug-and-play.
No modifications to the wiring are needed.

I had to reprogram the compass zone since the mirror was shipped
from a different part of the country but that was easy.  I first
thought that the compass feature was broken because it was telling
me the wrong directions.  It took a while of driving around to
recalibrate itself, and now it's all good.  Now I have a working
auto-dim mirror again and the compass is a nice addition.  I noticed
that the red LED compass readout itself also auto-dims with the
ambient light.  Nice.

See my S4 website for a couple of pictures of the mirror:

	http://www.amb.org/ti/audi/autiq/autiq-2.html

If any of you encounter a malfunctioned auto-dim rearview mirror, 
this would be an excellent upgrade.

-Ti