Alternator questions (long, sorry)

[Perry, Christoper (EDS)]

Hey all,
A couple of days ago I posted about the brushes in my alternator going bad.
Well I pulled the alternator and removed the regulator/brush assembly and
yup the brushes were really worn.  I called around and found that the Bosch
regulator was 80.00 so I wasn't excited about it.  I looked in the FA and
saw that the same part number applies to the regulator assy. in both my 90q
and a Passat.  Now my parents happen to have a non-running  1990 Passat with
a nearly new voltage regulator in it so I go over to their place and grab
the  regulator.  The regulator is a KAE made in Germany (the Bosch was made
in Spain??) and it, of course fit right in.

So I throw the alternator back in and start her up and...nothing, still 11.5
volts.  I then revved the engine to 2k rpm and bingo 14.5 volts.  So I am
all excited and take it out for a test drive.  Everything is OK until I get
out on the road and shift into second then it drops back to 11.5 volts.  So
I turn off all but the headlights and go home.  I went to the Bentley (NO
HELP!!!!!!!!) and ran through their checklist.  I noticed that my alternator
light was not coming on so I did the " remove wire from D+ connector and
ground it (wire, that is)" , key to on position, light not on hmm.  I found
the 10 point connector under the dash (not in the engine compartment like
Bentley says) and check for continuity between it and the alternator, its
good.  I think maybe my alternator warning light is burnt out so I pull the
instrument cluster.  Nope light is good.  I even went so far as to dismantle
the cluster to check the wiring traces, all good. I check for continuity
between the 10 point connector and pin 13 on the yellow 26pin connector for
the instrument cluster, it is good. I do an end-to-end continuity check from
pin 13 on the yellow connector to the end of the wire at the alternator, it
is good.

Starting to get frustrated here.  I put the instrument cluster back in and
ground the alternator exciter wire again. Lo and behold I have a alternator
warning light.  I put the exciter wire back on the D+ alternator terminal
and turn the key to the on position and wow, I still have the alternator
warning light.  I start the car, warning light goes out, still 11.5 volts.
Revv. it to 2K rpm still no change.  At this point I notice that the lights
behind the clock and the fuel gauge have stopped working.  I swear, look at
my watch, see that it is 1:30 am and give up for the night.

The next day at work I theorize that the new regulator's brushes may not fit
in the old alternator's deep grooves.  When I get home I pull the alternator
again  and pull the new regulator.  My suspicions are confirmed when I see a
very small wear pattern on the new brushes. I use some sandpaper to make the
new brushes narrower and put the whole thing back in.  I start the car and
am very pleased to see 14.5 volts, cool.  I rev it and it stays at 14.5
volts, yeah.  I go for a test drive and just as soon as I get it into second
gear it drops to 11.5 again, I'm pissed.  I pull back into the garage, turn
the key off and then back to the ON (not start) position and notice I don't
have an alternator warning light, WTF!!!!???  The entire time my voltage is
dropped the alt. warning light does not come on like I think it should.

Anybody have any ideas or an alternator schematic?  Could something actually
be bad in the alternator?  Diodes?

Any help appreciated.

Thanks,
Chris Perry