Alternator brushes/voltage regulator (87 5kcstq), kinda long

[MSV96 <MSV96@aol.com>]

This past Saturday my autocheck was displaying the oil iconwhen the motor was
not running...hmm. Level was okay (though I planned to change it Sunday
anyway), and I thought this was for pressure only, of course with engine not
running...big doh! for HAL. Anyway, later on the low battery icon came on. I
immediatly went to my climate control channel 11 and verified that indeed, no
charging. More hmm. I never saw the battery light come on though. After
reviewing Bentley, I also noticed that the battery light was not coming on
with ignition on, motor not running. I felt based on this and reviewing
Bentley's tests the brush/voltage regulator was suspect (and in stock at a
local Kragen for a whole bunch less than an alternator).

Sunday AM I go under the car to remove said regulator (before going to buy the
new part) only to find that the turbo oil line was in the way of removing the
alternator air duct cover. (Isn't working on Audis fun?!) Okay no big deal I
say, I was gonna change the oil now anyway. Anyone get that cover off without
removing the oil line? If so, how?! Anyway, I get there, remove the thing, and
head off to buy the new (generic non-German) one. The old brushes are worn,
but not below the "wear limit" as stated in Bentley. I assume that the "wear
limit" increases on older alternators cuz of wear on the armature? The old
regulator transistor biases on (with a Fluke on diode test range) like a it is
a darlington (is it?) but the new one biases on like a normal transistor. Now
I'm getting paranoid...alternator here we come. Installed the new one, re-
assembled and filled with new oil...and all problems are gone! Regulating now
at 14vdc and no more oil icon with no motor running. All in all not so
bad...just a very time consuming oil change.

The moral of the story is the auto-check system did indeed alert me that my
charging system had died BEFORE my battery failed--nice job Audi! I am curious
why the battery light never came on though, is that a normal mode of failure
when the brushes and/or regulator die? The failure was sudden...I have read
all the warnings here about checking them brushes, now I understand why! 

Thanks to all here, and especially Dan for this wealth of knowledge we share
on this here list. I knew just where to go (or at least thought I did, and was
lucky) and may not have without the list.

Mike Veglia
87 5kcstq