Alternator problems

Hello all! It's been a while since my last posting, but now I'm back
working on the bugs. A friend of mine has a 74 standard bug which has
some electrical issues. A few months ago he burned most of the wires on
the engine compartment as well as a stereo. Now I'm helping him replace
the harness and found a few issues.

A PO installed an external regulator (he has a Bosch alternator), for
some reason we don't know. And all the cables coming out of it are
burned. I just removed the regulator and all of the wires in the engine
compartment. Rewired everything and noticed the plastic brush holder
with the D+ terminal was melted. Removed the alt. opened it and just as
I suspected, the brushes were touching each other. I guess that was the
source of all the problems. Replaced the brush holder with a new one
and since the internal regulator looked fine (I don't know how to test
it) decided to connect it and try. Here's where it get's funny. The gen
light stays on even when the ignition is off (ie, no key) and the alt
does not charge the battery. I connected a piece of wire directly from
the D+ to the dash light and another one from the B+ to the battery and
it still stays on. I guess there must be some short inside the alt. or
maybe the internal regulator is bad. How do I test it? What else could
be wrong?

TIA,
Karls

It sounds like one of the diodes in the diode pack is burnt out letting
power flow both ways rather than one was as designed.

Tony

Karls wrote:
> Hello all! It's been a while since my last posting, but now I'm back
> working on the bugs. A friend of mine has a 74 standard bug which has
> some electrical issues. A few months ago he burned most of the wires on
> the engine compartment as well as a stereo. Now I'm helping him replace
> the harness and found a few issues.
>
> A PO installed an external regulator (he has a Bosch alternator), for
> some reason we don't know. And all the cables coming out of it are
> burned. I just removed the regulator and all of the wires in the engine
> compartment. Rewired everything and noticed the plastic brush holder
> with the D+ terminal was melted. Removed the alt. opened it and just as
> I suspected, the brushes were touching each other. I guess that was the
> source of all the problems. Replaced the brush holder with a new one
> and since the internal regulator looked fine (I don't know how to test
> it) decided to connect it and try. Here's where it get's funny. The gen
> light stays on even when the ignition is off (ie, no key) and the alt
> does not charge the battery. I connected a piece of wire directly from
> the D+ to the dash light and another one from the B+ to the battery and
> it still stays on. I guess there must be some short inside the alt. or
> maybe the internal regulator is bad. How do I test it? What else could
> be wrong?
>
> TIA,
> Karls
>

Thanks Anthony. How do I confirm this is the problem? Possible
solutions?

Karls

Karls wrote:
> Thanks Anthony. How do I confirm this is the problem? Possible
> solutions?
>
> Karls
>

Look on my web site for alternator internal info.
http://www.nls.net/mp/volks/htm/elec.htm

If the main diode pack has one bad diode,
the GEN light will stay on.

Replacing the diode pack is usually a hefty job.
You may be ahead of the game on this one by replacing
the whole alternator, especially since the regulator
could be bad.

And get rid of the extra regulator.

Speedy Jim
http://www.nls.net/mp/volks/

Karls wrote:
> Thanks Anthony. How do I confirm this is the problem? Possible
> solutions?
>
> Karls

The problem is that if the diode pack is the problem, the only place to
get them is to buy a rebuilt alternator.

Anyway with an ohm meter or battery powered test light, connect one test
lead to the positive output of the diode pace and touch the other lead
to each of the 3 AC inputs. Yous should get the same result on all 3 AC
inputs. Either you get continuity or not on all three. Now reverse the
test leads (still working with the positive output and the AC inputs)
and your results should be the opposite. Assuming the positive side
tested good, now it's time to test the negative side. Do the same but
working from ground to the 3 AC inputs.

Odds are a visual inspection will show an obviously burnt diode.

Tony