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From: John De Armond
Subject: Re: Replacement part for alternator?
Date: Tue, 31 Aug 1999 18:34:53 EDT

"Andrew_R._Mitz" wrote:
> Thanks for the comments.  Perhaps my 100 Watt ham radio
> in the car has some effect.  Meanwhile, back to  my
> original question.  Where can I get the replacement
> electrical components to fit that generator?

Depends on whether you're a ratchet-jaw or not.  Some of these
modern small alternators can produce high peak currents to bring the
tiny battery back up quickly but cannot cool well enough to sustain
a near full load indefinitely.

One more bit of advice.  In the last few years Wall Street types 
have moved into the reman industry en masse.  The result has been
that rebuilt parts have gone from merely mediocre to totally
unusable.  Last 4-seasons reman compressor I bought still had
sandblasting sand under the port caps.  As did the replacement for
it.  Nowdays if I can't find an OEM part at the junkyard, I buy new.

More to the point of your question.  Some of the large chain auto
parts stores sell rebuild kits.  Diode packs and regulators are also
generally available.  didn't catch the year model of your car but it
generally takes 3-5 years for this stuff to start showing up.  If
your friendly local auto parts store doesn't have 'em, check the
phone book for alternator/starter rebuilding services.  They might
sell you the parts, though you might also find their prices so cheap
as to not be worth the labor.

Rebuilding your unit may not solve the problem.  I ran into a
similar situation on my 75 Datsun 280z when it was fairly new.  Was
also running a rather high powered ham rig in the car.  Denso had a
bad run of diode packs that were debonding and failing in service. 
Lost a couple of bridges even before the ham rig.  What I did was
remove the bridge, buy some 100 amp, 400 volt stud rectifiers (3 ea
anode studs and 3 ea cathode studs) and a heat sink, brought the 3
phase leads from the stator coils out to the bridge and wired up an
external rectifier.  That alternator used an external regulator but
if it had not, I would have pulled the regulator out too.  That
bridge rectifier is still working just fine in that Datsun.  If you
go this route, take your alternator's nominal rating and double that
amperage to spec your diodes.

In the "good old days", the solution to unusual loads such as yours
was to install an "ambulance" (high capacity) alternator.  Space is
so tight in modern cars that this is generally not an option so
other steps must be taken such as moving the bridge outside the
alternator case.

From: John De Armond
Subject: Re: Replacement part for alternator?
Date: Wed, 01 Sep 1999 04:11:21 EDT

Mark Aarabi wrote:
> Neon John wrote:
> > Last 4-seasons reman compressor I bought still had sandblasting sand
> > under the port caps.  As did the replacement for it.
> In my opinion, there is no automotive product (of any kind) on the
> market with a reputation worse than 4-seasons.  They are pure junk,
> junk, junk!
> -Mark

Oh, don't get me started on those pricks.  The problem is, in my
area there is literally NO other alternative.  My friend who owns an
independent auto parts store tells me that he has no idea as to any
other alternative. Says 4-seasons has bought up all the
competitors.  Ditto with EVERY other store I've called or visited. 
If you have a suggestion for an alternative, I'm all ears.

One of my great other disappointments has been to see Delco's name
plastered on the same old reman crap.  My friend proudly advertised
his carrying the Delco Reman line.  The first two alternators I got
were just like the no-name crap - sandblasting grit in the stator,
brush dust still present around the slip rings, mounting bolt broken
off, sandblasted over and painted in one of 'em.  Screw that. Life's
too short to deal with these kinds of comebacks.


From: John De Armond
Subject: Re: Measuring Alternator Output.
Date: Fri, 16 Jun 2000 17:42:19 EDT
Newsgroups: rec.outdoors.rv-travel

Eric Roellig wrote:
> All,
> I need some suggestions from some of you problem solvers.
> I seem to be going through alternators at an alarming rate all of a
> sudden. The original 95amp alternator on my '93 Ford E150 van started to
> provide some higher voltages than normal so I had it swapped out.
> The first replacement (Napa 95amp rebuild) lasted 3 driving hours then
> started providing 17 volts. We could also smell something "burning".
> The second replacement (Auto Zone Duralast 130amp) lasted about 1 second
> (it decided to eat itself...) I know, I should be suspicious as hell
> about something called "Duralast" but all I could find open (Memorial
> Day weekend out-of-town) was Auto Zone... :(
> The third replacement (Auto Zone Duralast 130amp) lasted a couple of
> weeks. It just gave out (accompanied by the smell of burning electronic
> parts.) At the time it burnt out I was coming home with some reasonably
> depleted golf car batteries (11.2volts at load), lights on and front and
> rear AC blowers running hard. I have an 8 gage wire running the length
> of the van to the trailer plug.
> Fourth replacement (Auto Zone Duralast 130amp) is currently working but
> I have been limiting loads until I can figure out what (if anything) is
> going on.
> My mechanic thinks I may be pulling the alternator too hard. I didn't
> have any problems with the original 95amp alternator for 4 years under
> similar conditions.

Your mechanic is correct.  Conventional alternators are not designed
to sustain anywhere near their rated outputs continuously. A mostly
discharged set of golf cart batteries is close enough to a
continuous load for this discussion.  This is something that I had
to be re-taught after equipping my rig with large batteries :-( 
Look at the size of a semi truck 100 amp alternator (the size of a
lot) to see what is required for continuous full rated output.

> An Auto Zone manager warned me that the alternator lifetime warranty
> will not be honored much longer at this rate!!
> I would like to put an ammeter on the van after the alternator to see
> how hard I am pulling it. Anyone know where I can get a meter to handle
> 130amps or so? Best I (or my mechanic) can find is a +-60amp meter.
> Idealy, I would like to find one that uses a shunt so I don't have to
> run a high current wire all over the place.

Probably the cheapest device that you can get is a clamp-on DC
ammeter.  Cost is in the $100-150 range.  Shunts are available - I
have several - but are a pain to use as test instruments because
they must be wired in.

> Any better ideas? My mechanic will test the load from just the van (it
> would be a pain in the elsewhere to take the trailer there + the
> batteries are charged up now) but I want to be able to monitor things in
> real time while on trips & such.

Well, the cheap and dirty way to address the problem is to insert
some resistance in the trailer wiring to limit the current available
for charging.  A better solution is the one I did on my rig, fitting
a heavy duty alternator.  I couldn't get a semi alternator to fit so
I selected the next best thing,  a 160 amp alternator from a late
model Cadillac.  This particular alternator is designed to supply a
substantial portion of that 160 amps full time because that car is
such a power hog.  The thin film defrost coating on the windows
draws something like 60 amps all by itself.

A better solution if you have the room is to fit a semi-truck
alternator.  A 100 amp unit would probably fit with only some
bracket modification and would carry the freight all day long.

Something I've done in the past for high continuous load
applications is to strip all the electronics out of the alternator
and mount them external.  An external diode bridge is as simple as 6
200 volt, 200 amp stud diodes on a couple of heat sinks.  The NAPA
external solid state replacement regulator for 68-70 Mopars is a
nice regulator that will work and has an internal voltage

Since you're eating alternators at the rate you are, I suggest
getting some resistance in the trailer circuit - a coil of suitably
sized hookup wire will do.  Get the clamp-on ammeter so you can tell
what you're doing.  Then contemplate a better, long term solution
involving a larger alternator.


From: John De Armond
Subject: Re: Maximum Field Current for Delco 10SI Alternator?
Date: Tue, 01 Apr 2008 15:30:24 -0400
Message-ID: <>

On Tue, 1 Apr 2008 08:07:11 -0800, "Ulysses" <> wrote:

>OK, thanks.  I think I understand that now.  My confusion seems to stem from
>something an auto mechanic once told me: there is a slot on the back
>(non-pulley) side of some alternators and if you stick a screwdriver in
>there it will "have full output."  Well, after having taken apart my
>alternator and studying what's inside the only thing I could see is that it
>might test to see if the negative brush is bad.  Did I miss something?

Like most of those shadetree "tricks", there is a kernel of truth but also the
ability to let lots of blue smoke out.  There are two major architectures of field
regulation - high side and low side.  High side regulation has the regulator between
the battery and field with the other side of the field grounded.  The battery
attaches to the field on low side regulation and the regulator goes between the other
side of the field and ground.

IFF the alternator uses low side regulation AND the regulator brush is closest to the
housing then sticking that screwdriver in there and shorting the brush to ground will
turn the alternator full on.

OTOH, if the system is high side regulated, the screwdriver will either do nothing if
it hits the grounded brush or blow the regulator if it hits the other one.


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