Alternator charges until warm then stops charging

RF_Burns

RF_Burns

Super Moderator
Staff member
Sep 7, 2008
5,151
1,354
113
Ontario Canada
Does your GEN light come ON when it stops charging?

The Delco alternator is pretty easy to fix. You can buy a kit with the electronic modules, bearings etc.

You can download the alternator testing and service manual here:
https://www.gmcmhforum.com/resources/delco-alternator-service-manual.15/

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
Hi Ben,
I went to the single wire alternator and I really like it. But you will need to replace your stock battery isolator to a battery combiner. I went with
a marine style combiner.
If your Thinking about changing it, might as well do it now.
Scott.

--
Scott Nutter
1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final drive, Quad bags, tankless water heater, everything Lenzi. Alex Ferrera
installed MSD Atomic EFI
Houston, Texas
 
The internal Voltage regulator increases trim with decrease in temp and decreases Voltage trim as temp rises. Yours may he bad and over reacting. How
did you come to this conclusion.? Where are you metering if so? I would start by cleaning connections on 2 pin that feeds internal regulator just to
rule that out.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
I agree with John. It sounds like the thermistor inside your voltage regulator is failing.
Usually my alternator puts out 14.5 volts when cold and then drops to 13.8 as it warms up.
--
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
 
My experience has been the positive jumper from the diode bridge to the output terminal get loose in the poorly designed stud and insulator that goes
through the housing, when it get hot it get loose, and the looser it gets, it gets hotter, the loose then hotter just an endless cycle, Mine actually
eventually burnt into inside.
Had to get a jumper from a scrap alternator and came up with an insulator setup that could be tightened up, the best bet I think is the one wire
alternator now available, when the time comes I'll go to that.

Skip Hartline

--
74 Canyon Lands, FiTech,
3.7 FD, Manny Tranny,
Springfield Distributor,
2001 Chevy Tracker Ragtop Towd
 
Good write up on the differences between a one wire and a three wire
alternator here:

http://www.madelectrical.com/electricaltech/onewire-threewire.shtml

Eric

On Mon, Mar 2, 2020 at 2:01 PM Skip Hartline via Gmclist <

> My experience has been the positive jumper from the diode bridge to the
> output terminal get loose in the poorly designed stud and insulator that
> goes
> through the housing, when it get hot it get loose, and the looser it gets,
> it gets hotter, the loose then hotter just an endless cycle, Mine actually
> eventually burnt into inside.
> Had to get a jumper from a scrap alternator and came up with an insulator
> setup that could be tightened up, the best bet I think is the one wire
> alternator now available, when the time comes I'll go to that.
>
> Skip Hartline
>
> --
> 74 Canyon Lands, FiTech,
> 3.7 FD, Manny Tranny,
> Springfield Distributor,
> 2001 Chevy Tracker Ragtop Towd
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
The steel jumper to the output terminal loosened and give me issues last summer. I replaced the steel jumper with 2 copper straps in parallel. The
copper straps were made from copper pipe fastening strap. Not sure why they would use steel, likely cheaper.

I replaced the melted plastic insulating washers with nylon insulators from the electronics industry. Works fine so far.

I can't see where the 1 wire will fix this issue.

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
One thing you might check. If you can get it to fail, meter the voltage into the isolator and out of the isolator on both terminals. It only takes a
minute to check all 3. Use the the aluminum plate the isolator is mounted on for the negative lead of your meter.

I am thinking that maybe one of the diodes in the isolator is braking down as it warms up.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
I understand the logic behind wanting to simplify the electrical system on
the GMC. Just be absolutely sure that what you are doing will actually
improve and simplify your coach. An isolator is a very, very reliable
device. And in the rare event of it failing, it is easy to troubleshoot,
and to replace. Most electrical issues in GMC's can be attributed to the
fact that they are all 40 plus years old, and every electrical connection
in the coach has at least some issue with corrosion, or loose
connections, just basic stuff that occurs from age and inactivity and
inattention.
Replacement engine alternators from rebuilders that use inexpensive
off-shore produced reproduction parts are a huge fail point. Seen it, dealt
with it, hate it.
Jim Hupy
Salem, Oregon

On Mon, Mar 2, 2020, 4:01 PM Eric Mears via Gmclist
wrote:

> Good write up on the differences between a one wire and a three wire
> alternator here:
>
> http://www.madelectrical.com/electricaltech/onewire-threewire.shtml
>
> Eric
>
> On Mon, Mar 2, 2020 at 2:01 PM Skip Hartline via Gmclist <

>
> > My experience has been the positive jumper from the diode bridge to the
> > output terminal get loose in the poorly designed stud and insulator that
> > goes
> > through the housing, when it get hot it get loose, and the looser it
> gets,
> > it gets hotter, the loose then hotter just an endless cycle, Mine
> actually
> > eventually burnt into inside.
> > Had to get a jumper from a scrap alternator and came up with an insulator
> > setup that could be tightened up, the best bet I think is the one wire
> > alternator now available, when the time comes I'll go to that.
> >
> > Skip Hartline
> >
> > --
> > 74 Canyon Lands, FiTech,
> > 3.7 FD, Manny Tranny,
> > Springfield Distributor,
> > 2001 Chevy Tracker Ragtop Towd
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Bruce
Tried to open the Delco service manual and a banner read Do not have
permission to down load.
Do I have to sign up to get the information?

On Sun, Mar 1, 2020 at 4:26 PM John R. Lebetski via Gmclist <

> The internal Voltage regulator increases trim with decrease in temp and
> decreases Voltage trim as temp rises. Yours may he bad and over reacting.
> How
> did you come to this conclusion.? Where are you metering if so? I would
> start by cleaning connections on 2 pin that feeds internal regulator just to
> rule that out.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
 
Thanks Bruce
😀😀

On Mon, Mar 2, 2020 at 10:22 PM Bruce Hislop via Gmclist <

> Sorry Bruce, Try this one:
> http://www.gmcmhphotos.com/photos/data/6522/Delco_Alternator.pdf
>
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
 
Bruce Hislop question having done several Delcotrons over the years. Is there a correct procedure for separation of the case without getting the
brushes stuck on the slip rings? I understand the reassembly with brush retainer wire "tool" or spray straw. Seems more difficult to get them apart
on newer units like CS144. Last time I cracked brush holder and had to replace. Thanks.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
John,
I don't have any experience with the CS144 model you mentioned.

A quick google search came up with this video showing the repair of a CS144. The case just pulled apart with no issues or mention of issues with the
brushes. I could not see any ridge which the brushes would catch on.

https://alternatorparts.com/cs144-alternator-repair-video.html

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
> Hello All! I'm new here and this is my first post!
> I'm hoping to draw from the experience from the community to understand why the alternator in my 76 Palm Beach charges are over 14 volts for about
> 5 minutes and then stops charging all together.
> Ideas for a fix? I'm looking into a single pole alternator replacement...
> Thanks in advance!
>
> Ben

Ben,

Welcome to the group, family, cult, asylum......

While there has been a lot of discussion, I would like to know more about how you determined that it has stopped charging. Things like where you are
measuring 14 volts and with what? This does not mean I doubt you, it just means that we might be able to better determine the cause and the best
cure.

Speaking of cures, a single wire alternator is not a cure for anything and it will leave you with a less capable electrical system. I have done a lot
of boat work for owners. Most of it was transforming racing sloops into performance cruisers. That means installing a comfortable house electrical
system among other things. While combiners and neat and trick and stuff, over the years I have replaced many more of those than isolators.

The small frame 27SI alternator is a very capable machine. In cold situations, the 80Amp version can kick out 98 (measured) for short periods. What
I would like to see would be the voltage at the alternator output (also the center pole of the isolator) when you think it has stopped charging. If
it has actually shut down, that is the regulator as Bruce suggested.

Now, back to Ben for a moment. This is a community of helping and very supportive people the like of which is very rare. You will quickly learn that
just about everybody here has a not-so-hidden agenda. That agenda is to see that you get to understand an and enjoy what your coach can be and do for
you. It is a lot more than just a big new toy because it connects you to this community. The only way to annoy these people is to not pay attention
to what get written here. We have a few original owners and many with decades and several hundred thousand miles of experience. They want to help.
If you have a problem and one is in striking range, he may just show up to be a friendly mentor.

To this end and as you are working the forum, please fill in a sigfile. To do this, go up to and then down to
. There you will fine a "Signature" box. Please fill in a real name because all we have is Ben, then a bit about the coach. We have 76
Palm Beach but does it have any important mods that may matter? Finally, a geographic reference so that if you have help nearby, they will know it
too. (And you may get an invite to join a local chapter. If you do, try to meet up with them.)

I told you that this was a supportive community, and the only one I have ever known like this is that of the watermen that are my world. For that
reason. I like to welcome new owners here with a paraphrase of the welcome you would get there. So,

May the Good Lord bless this coach and all those that set forth within her.
Welcome Ben

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
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Applied GMC
GMCMI Fall 2026 Rally

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