Alternator/Charging Problem -- HELP! :(

[archive@porknet.ml.org (Toby Reed)]

Hey all,

I just bought and installed a new battery about 3 days ago. It was
charged to 12.45 volts when purchased. I've only driven about 20 miles
with it connected.

As I was driving around tonight at 40mph @ 2900 rpm I glanced at my
instrument cluster and noticed the alternator/battery light was glowing
slightly. When I came to a stop sign and my engine returned to idle at
900 rpm, the light was on with full intensity. Then I revved to 4000 rpm
in 1st and it faded completely off. I disregarded it as a loose wire or
something similar and drove home. When I got home I turned off the engine
and popped the hood, then started the engine again. It would not start. I
checked the voltage at the battery terminals... it was 11.68V. When I
disconnected the ground wire and it was 11.69V. I finally got it started
(after 5 tries or so) and each time as I revved it in neutral, the light
faded from full brightness at idle to completely off at about 4000 rpm. I
then checked the voltage at the alternator with several different grounds
(intake manifold, battery - terminal, sheet metal near radiator) and they
were all the same at 11.91V... kind of low for alternator output IMHO. It
was late and my exhaust leak is noisy so I didnt get a chance to check
voltage when I revved the engine, but my guess is that it would go up.

Ignoring me and the alternator light, my clueless friend concluded that it
was a bad starter motor. I'm left thinking its one of the following:
1. Bad Regulator	(~$25)
2. Bad Alternator	(~$60-$100) :(
3. Bad Alternator Bushings/Brushes	(?)

Hopefully its a bad regulator, since they're only $20 or so. It could be a
bad alternator if the alternator is only putting out an idle voltage of
11.9 volts and it increases with rpm. The alternator belt looks okay...its
spinning and everything. No funny noises. Though I did smell something
that smelled like burning electronics when I opened the hood, just for an
instant.

The alternator looks like a stock Bosch unit. The car has 124k miles on it
and most of the parts are original. I can't find any part numbers on the
alternator, but it says "Autobahn" on one part of the label and evidently
its a remanufactured alternator.

If it ends up being a bad regulator I'm going to replace it with an
adjustable one...

I just cleaned the alternator positive wire two days ago. It was corroded
a bit and part of the terminal was rusted. But when I started the engine
and tested the voltage at the alternator it was 14.1V, good enough. I have
a newly-added 4 gauge ground at the transmission housing. I also have new
battery terminal clamps to go with the new battery, and newly stripped
and clamp-compressed positive and ground wires.

I was going to add a ground wire between the metal casing of the
alternator and some nearby sheet metal, but the resistance between the two
when I checked with my ohm meter was like 0.01 ohms, so I'm not sure its
necessary.

I wanna get this baby up and running reliably, and get the alternator to
put out a full 14 volts. I'm also on a limited budget.

Any ideas on what the problem could be?

Thanks,

-Toby

'87 Flash Silver Metallic Scirocco 16V

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