Basic Electrical Question

Huw Powell human747 at
Fri Dec 20 22:57:16 EST 2002

> Thanks for getting back to me.

No problem.  Taking this public again, hope you don't mind.  others may
have ideas or similar problems.

> I'm checking the voltage on the smaller
> gauge (blue in this case) wire on what I thought was the D+ post.

Yup, that is the D+.

> I've had
> the ground wire from the meter on the flat copper-mesh wire bolted to
> chassis ground.  The larger of the posts is reading 22V (really) with the
> ground wire on chassis ground.  I'm certain that the meter is reading
> accurately...I just can't figure out what's corroded (open).  Please let me
> know if I'm not grounded to the right path.

Oh geez.  All I can think is something is floating, that is, not
properly referenced to some "common" gournd, and I don't think it's your
meter.  Generally, when making these sorts of basic charging
measurements, you should try to keep the meter grounded to the same
place for every measurement, and well grounded, none of this "kinda
holding the probe to some corroded bolt" stuff.  Holding it with a clamp
or clip to the battery "-" post is a good one, or jamming it into the
battery "-" connector if you can.

I think it might be amusing to see the voltage measurement to your
alternator case.  it might not be grounded very well anymore.  Ground is
the two case halves, conducted via the narrower metal part in the middle
of them, to the bracket, to the block.

The starter is grounded by its block/tranny mounting surface, and of
course the battery has that nasty, old corroded wire going to the
battery tray and then a tranny bolt.  I left a short tranny bolt to
batt. tray cable on mine and replaced the main ground with a nice cheap
2 GA cable to a tranny bolt (I had to drill out the tab a bit to
accomodate the huge bolt, but what the heck).  Cleaned all surfaces at
the same time.

By the way, your voltage regulator could be thrashed, also.

Hope this helps, and good luck...

> > > I have a quick question for you:
> > >
> > > Output of alternator is approximately 15.2V on the D+ post.  Battery
> voltage is 12.5V (engine running). All electical contacts in the
> charging/starter system have be thoroughly cleaned.
> > >
> > > Where's the (connectivity) break? TIA
> >
> > > 84 4ksq
> >
> > You are getting 15.2 volts at the trigger wire?  D+ is not the alt
> > output, the output is B+.
> >
> > Where are you grounding your meter in each case?

Huw Powell

More information about the quattro mailing list