'86 5KTQ: Bad alternator/voltage regulator? UPDATE

[Bares, Vittorio]

To verify if the exciter wire is ok - you can put it to ground while the
car is running. This should light up the Alt light on the cluster
(nothing to do w/the icon in the screen).

Vittorio -

-----Original Message-----
From: quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com]
On Behalf Of L DC
Sent: Wednesday, April 16, 2008 9:25 AM
To: audi at humanspeakers.com; Peter Golledge
Cc: quattro at audifans.com
Subject: Re: '86 5KTQ: Bad alternator/voltage regulator? UPDATE

Thank you all for your input on the alternator/
battery charging issues and I'm sorry for not updating
on it sooner  but was not able to get to it until
yesterday (Tuesday).

I performed the tests suggested by you all as well as
those outlined on Chris Miller's webtsite; 
http://members.aol.com/c1j1miller/electrical.html

I have not looked into the "battery cable splice" due
to the results I got so far;
http://members.aol.com/c1j1miller/index.html

These are the results I got.

With engine/ignition key off:

Battery charge:  12.25V
Jump start post:  12.25V
Alternator big wire stud:  12.25V
Exciter wire (little blue one):  no voltage

With ignition to key-on position only:

Same results as above, except this time the "Exciter"
blue wire showed 11.80V; normal as per the write-ups I
read.

As soon as the engine is started, voltage begins to
drop and after a 5 minute run at idle and slightly
revving engine volts falls to about 11.95V all across
the points tested, except for the exciter wire which
showed about .75 to 1V lower than the rest.

Now, regarding the exciter wire; it was on its way out
about 1 year ago so I replaced about 8 inches leading
to the alternator. The fact that is getting voltage
would mean is OK now, correct?

The trouble-shoot this time lasted about 40 minutes
and the battery charge ended at 12V. 

Also as per Miller's website:

"The instrument panel light bulb for the charging
system also should be checked if the alternator is not
charging, as current flows through this bulb, then to
the alternator field connection via the blue wire. If
the bulb gets burned out, the alternator may not
charge. The charging system light should come on when
the ignition key is turned to the first position,
before starting the engine."

I have not taken the instrument cluster out to find
out if the "panel light bulb" is fine but as I
explained above, if the excited wire is getting
current, wouldn't that mean the bulb is fine?

Also, regarding the "charging system light" does he
mean the battery icon affixed on the instrument
cluster or any other symbol on the LCD screen?
I performed the test thrice and on the first try, the
battery icon affixed on the instrument cluster, along
with others, did light up with ignition key to the on
position and went out as engine was started.

On the other two attempts leading to starting engine
and various just ignition-key-on attempts, the battery
icon did not light up at all? What the heck?

When the problem first manifested and drained the
battery after I stopped to refill gas, the VOLT+ icon
(encased by a battery outline) would flash on the LCD
screen. Shouldn't this icon flash as the car is
running indicating alternator not charging as suppose
to when car's battery is already drained?

Also, this VOLT+ icon did not show up while trouble
shooting the problem and did so only at the gas
station when I first learn of it. This time I did not
let the battery drain past 12V, so I don't know if
that would make a difference on the icon.

So what's the deal?

Is the alternator bad despite that I was told it is
good at two different places when I had it tested?

Many Thanks again!!

-Louis

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