GMCforum: GMCnet » Alternator Questions

Home » Public Forums » GMCnet » Alternator Questions

Show: Today's Messages :: Polls :: Message Navigator

Alternator Questions [message #139496]

Tue, 16 August 2011 17:11

larry.whisler

Messages: 356
Registered: August 2005

Karma: 8

Senior Member

The alternator in our 76 GMC stopped working indicated by the idiot light.

I had installed this alternator in 2007 with a 100 Amp Bosch rebuild from NAPA.

I took it apart and the recifier and triode were both fried.

Since this alternator was not that old ( but out of warranty ),
I decided to replace those components rather than replace the entire alternator.

I checked the stator and rotor for shorts and didn't find any.

I installed it today, fired up the coach and checked the ouput voltage. 17 volts. And the alternator was getting hot.

Is this a voltage regulator problem? Or something else?

Appreciate any advice.

larry whisler

Report message to a moderator

Re: Alternator Questions [message #139497 is a reply to message #139496]

Tue, 16 August 2011 17:22

roy1

Messages: 2126
Registered: July 2004
Location: Minden nevada

Karma: 6

Senior Member

if this is the voltage you are seeing with the battery in the circuit yes you have a bad regulator

Roy Keen Minden,NV 76 X Glenbrook

Report message to a moderator

Re: Alternator Questions [message #139498 is a reply to message #139496]

Tue, 16 August 2011 17:23

chasingsummer

Messages: 434
Registered: May 2011
Location: asheboro, nc

Karma: 0

Senior Member

larry,
could be same isolator rated thing i just went thru, look thru post just below this one related to charging issue, i had no idea this feed back wire thing to the alternator existed. i think i caught mine before it fried alternator.

brian asheboro, nc 75 eleganza, 74 build 119k miles and counting, DOG HOUSE

Report message to a moderator

Re: Alternator Questions [message #139500 is a reply to message #139497]

Tue, 16 August 2011 17:30

larry.whisler

Messages: 356
Registered: August 2005

Karma: 8

Senior Member

I was seeing 16.4 volts at the battery on a prior startup.

I shut it down and connected the volt meter directly to the alternator and restarted the engine. It climbed to 17 volts within 30 seconds and I shut it down.

Report message to a moderator

Re: [GMCnet] Alternator Questions [message #139503 is a reply to message #139498]

Tue, 16 August 2011 17:49

Mr ERFisher

Messages: 7117
Registered: August 2005

Karma: 2

Senior Member

nope is not the isolator.

I would have it rebuilt by a good local guy

stators normally open, not short, and they all are fried, but not
replaced by Napa and the others

good luck
gene

On Tue, Aug 16, 2011 at 3:23 PM, brian <chasingsummer@triad.rr.com> wrote:
>
>
> larry,
> could be same isolator rated thing i just went thru, look thru post just below this one related to charging issue, i had no idea this feed back wire thing to the alternator existed. i think i caught mine �before it fried alternator.
> --
> brian
> asheboro, nc
> 75 eleganza 2 74 build
> 118k miles and counting,
> DOG HOUSE
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>

--
Gene Fisher -- 74-23,77PB/ore/ca
�Give a man a fish; you have fed him for today --- give him a URL and -------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist

Report message to a moderator

Re: [GMCnet] Alternator Questions [message #139504 is a reply to message #139496]

Tue, 16 August 2011 17:51

Mr ERFisher

Messages: 7117
Registered: August 2005

Karma: 2

Senior Member

On Tue, Aug 16, 2011 at 3:11 PM, larry.whisler
<larry.whisler@hotmail.com> wrote:
>
>
> The alternator in our 76 GMC stopped working indicated by the idiot light.
>
> I had installed this alternator in 2007 with a 100 Amp Bosch rebuild from NAPA.

I had 3 bad ones in one week from Napa
get it rebuilt locally

and be sure they change the stator windings, also

gene
>
> I took it apart and the recifier and triode were both fried.
>
> Since this alternator was not that old ( but out of warranty ),
> I decided to replace those components rather than replace the entire alternator.
>
> I checked the stator and rotor for shorts and didn't find any.
>
> I installed it today, fired up the coach and checked the ouput voltage. �17 volts. �And the alternator was getting hot.
>
> Is this a voltage regulator problem? �Or something else?
>
> Appreciate any advice.
>
> larry whisler
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>

--
Gene Fisher -- 74-23,77PB/ore/ca
�Give a man a fish; you have fed him for today --- give him a URL and -------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist

Report message to a moderator

Re: Alternator Questions [message #139518 is a reply to message #139496]

Tue, 16 August 2011 18:48

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Larry,
I really hate to answer like this, but there is too much going on here....

larry.whisler wrote on Tue, 16 August 2011 18:11

The alternator in our 76 GMC stopped working indicated by the idiot light.

I had installed this alternator in 2007 with a 100 Amp Bosch rebuild from NAPA.

I took it apart and the recifier and triode were both fried.

There has to be something REALLY Wrong to smoke all those diodes.

Quote:

Since this alternator was not that old ( but out of warranty ), I decided to replace those components rather than replace the entire alternator.

I checked the stator and rotor for shorts and didn't find any.

And you separated each winding and checked of open and shorted turns? - if not, you may have missed something.

Quote:

I installed it today, fired up the coach and checked the output voltage. 17 volts. And the alternator was getting hot.

No surprise there, but it is also boiling your batteries.

Quote:

Is this a voltage regulator problem?

It could be, if you smoked all the diodes, why would you expect the the regulator is not damaged.

Quote:

Or something else?

It could also just be that the sense lead to the regulator is not connected where it should be.

Quote:

Appreciate any advice.

larry whisler

Matt

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

Report message to a moderator

Re: Alternator Questions [message #139529 is a reply to message #139518]

Tue, 16 August 2011 20:05

larry.whisler

Messages: 356
Registered: August 2005

Karma: 8

Senior Member

Matt,

Thanks for the response.

I checked each of the windings and they were okay.

Two of the three diodes were fried. These two were severly
corroded and I assumed that due to the corrosion, they were making poor contact and caused their destruction. I ran this coach for a few years without the inner fender liners and I am of the opinion that throwing all the rain, snow, salt, etc. up into the alternator from the driver's side front wheel is not a good idea. I would suppose that this is one very good reason to keep the liners installed.

I should have changed out the regulator, but it didn't appear damaged and I had no way to test. I have a new VR ordered for installation tomorrow.

I checked the sense wire prior to removing the alternator thinking that it could be the problem. Also checked the isolator. Voltages at all those points were in the correct range.

larry

Report message to a moderator

Re: Alternator Questions [message #139551 is a reply to message #139529]

Tue, 16 August 2011 21:37

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

I've been reading but not commenting. Now your last posting has me confused.

You state that you checked the sense line and the voltage was OK. To me that means 14 volts. At the same time you say the alternator is putting out 17 volts.

Where is the 3 volt drop? That is your problem.

Did you check the voltage at the sense line on the alternator or somewhere else on the coach?

Look for that 3 volt drop.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

Report message to a moderator

Re: [GMCnet] Alternator Questions [message #139611 is a reply to message #139496]

Wed, 17 August 2011 09:02

Tangerine

Messages: 192
Registered: February 2004
Location: Livonia, MI

Karma: 0

Senior Member

On 8/16/2011 6:11 PM, larry.whisler wrote:
>
> The alternator in our 76 GMC stopped working indicated by the idiot light.
>
> I had installed this alternator in 2007 with a 100 Amp Bosch rebuild from NAPA.
>
> I took it apart and the recifier and triode were both fried.
>
> Since this alternator was not that old ( but out of warranty ),
> I decided to replace those components rather than replace the entire alternator.
>
> I checked the stator and rotor for shorts and didn't find any.
>
> I installed it today, fired up the coach and checked the ouput voltage. 17 volts. And the alternator was getting hot.
>
> Is this a voltage regulator problem? Or something else?
>
> Appreciate any advice.
>
> larry whisler
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
On my return trip from Virginia last week I had the same problem. I
drove 6 hours with that light glowing bright. It only brought down the
engine battery by a half a volt. The house battery was down to 10.5
volts. It had to run the refer. I had installed a rebuilt Alternator
from Murry's discount auto in 2006. It was only 5 years old. I paid on
sale $71.00 for a 100 amp. Came with a life time warranty. Well
Murry's has been bought out by O'Reilly's. I took the bad alternator in
and they replaced it with a new rebuilt one. The price would have been
$161.00. The failler was the insulation around the large wire that
would feed the battery. It melted and shorted out.
Gary W. Mills (Livonia MI)
. ___________
./_][__][] []| 1974 GMC M/H
.*O-------OO-* Painted Desert
"Tangerine Dream" W/New Frame

_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist

1974 GMC 260
Tangerine Dream
Livonia Michigan

Report message to a moderator

Re: [GMCnet] Alternator Questions [message #139620 is a reply to message #139611]

Wed, 17 August 2011 09:59

USAussie

Messages: 15912
Registered: July 2007
Location: Sydney, Australia

Karma: 6

Senior Member

Gary,

About 25 miles south of Knoxville heading for Chuck Boyd's I noticed the Alt
light flicker and go off. About 20 miles it flickered again and stayed on a
bit. About 15 miles it came on and stayed on for a couple of miles. At 10
miles it was ON. As I got closer I watched the voltage drop and drop. Got
about 2 miles from Chuck's I stopped at a light. Light turned green I hit
the gas and it died. Damn! Now what! Thought for a second and realized I
could go out and throw the switch that jumps the BOOST switch. I started to
unbuckle my seat belt when the bulb above my head came on. Reached over and
hit the BOOST switch and cranked it up. VROOOOOM - off we go to again. Made
it to Chuck's where he helped me install the spare I got from JimK. Funny
moment - for the life of us due to the ram air cleaner hose we couldn't seem
to get the alternator out. I tried - NADA - Chuck tried - NADA. I went
outside to see if I could get it out from underneath. I got halfway across
the front end when I heard a clunk followed by "oops!" The alternator had
slipped out of Chucks grip and fell out. We now know how to remove an
alternator from Double Trouble - it has an automatic release system! When we
looked at the alternator we saw that the lug in the alternator that sends
power to the battery had melted the insulation around it and was shorted
out.

Regards,
Rob M.

-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Gary Mills
Sent: Thursday, 18 August 2011 12:03 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Alternator Questions

On my return trip from Virginia last week I had the same problem. I
drove 6 hours with that light glowing bright. It only brought down the
engine battery by a half a volt. The house battery was down to 10.5
volts. It had to run the refer. I had installed a rebuilt Alternator
from Murry's discount auto in 2006. It was only 5 years old. I paid on
sale $71.00 for a 100 amp. Came with a life time warranty. Well
Murry's has been bought out by O'Reilly's. I took the bad alternator in
and they replaced it with a new rebuilt one. The price would have been
$161.00. The failler was the insulation around the large wire that
would feed the battery. It melted and shorted out.
Gary W. Mills (Livonia MI)

_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist

Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426

Report message to a moderator

Re: Alternator Questions [message #139624 is a reply to message #139551]

Wed, 17 August 2011 10:09

larry.whisler

Messages: 356
Registered: August 2005

Karma: 8

Senior Member

Ken Burton wrote on Tue, 16 August 2011 21:37

I've been reading but not commenting. Now your last posting has me confused.

You state that you checked the sense line and the voltage was OK. To me that means 14 volts. At the same time you say the alternator is putting out 17 volts.

Where is the 3 volt drop? That is your problem.

Did you check the voltage at the sense line on the alternator or somewhere else on the coach?

Look for that 3 volt drop.

I need to clarify these statements. Before removing the alternator, I checked the sense, idiot lite, and battery wires to the alternator. They checked out ok. Low voltage to the idiot lite and battery volts at the other two. I performed these tests to check the wiring. At that point, I figured the problem was in the alternator.

After replacing the components and installing the alternator,
I was getting the 17 volts at the Bat connection and at the sense line. I didn't bother checking the idiot lite wire for voltage.

I just pulled the alternator. Rechecked the continuity on the stator and rotor. those are fine. Now I am off to NAPA for a new volt regulator.

larry whisler

[Updated on: Wed, 17 August 2011 10:14]

Report message to a moderator

Re: Alternator Questions [message #139649 is a reply to message #139624]

Wed, 17 August 2011 14:04

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

OK.. Sorry. Ignore my previous posting...

Ken B.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

Report message to a moderator

Re: [GMCnet] Alternator Questions [message #139650 is a reply to message #139620]

Wed, 17 August 2011 14:10

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

What causes the insulator to melt?

Answer: heat.

What causes high heat there?

Answer: loose connection

That connection needs to be CLEAN and TIGHT. The saem goes for the crimp connection on the wire. Any slight resistance there with an occasional 80 to 10 amps across it will cause a lot of heat very quickly.

Yours, and the previous posting, are not alternator failures. They are installation / connection failures.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

Report message to a moderator

Re: [GMCnet] Alternator Questions [message #139689 is a reply to message #139650]

Wed, 17 August 2011 19:22

USAussie

Messages: 15912
Registered: July 2007
Location: Sydney, Australia

Karma: 6

Senior Member

Ken,

I agree with the requirement about the clean and tight connections, however,
IIRC in my case it was tight. I don't remember checking the cleanliness but
removing, cleaning, putting some of grease that used to resist corrosion and
then tightening it just went on my list of TTD when I get back.

Chuck, do you remember if it was tight?

Regards,
Rob M.

-----Original Message-----
From: Ken Burton

What causes the insulator to melt?

Answer: heat.

What causes high heat there?

Answer: loose connection

That connection needs to be CLEAN and TIGHT. The saem goes for the crimp
connection on the wire. Any slight resistance there with an occasional 80
to 100 amps across it will cause a lot of heat very quickly.

Yours, and the previous posting, are not alternator failures. They are
installation / connection failures.
--
Ken

_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist

Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426

Report message to a moderator

Re: [GMCnet] Alternator Questions [message #139690 is a reply to message #139689]

Wed, 17 August 2011 19:31

emerystora

Messages: 4442
Registered: January 2004

Karma: 13

Senior Member

>
> From: Ken Burton
>
> What causes the insulator to melt?
>
> Answer: heat.
>
> What causes high heat there?
>
> Answer: loose connection
>
> That connection needs to be CLEAN and TIGHT. The saem goes for the crimp
> connection on the wire. Any slight resistance there with an occasional 80
> to 100 amps across it will cause a lot of heat very quickly.
>
> Yours, and the previous posting, are not alternator failures. They are
> installation / connection failures.
> --
> Ken

Ken

I had an alternator fail at that same insulator BUT it was the internal connection that was loose and burned. NOT the outside connection that I had any control over.

Emery Stora
77 Kingsley
Santa Fe, NM

_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist

Report message to a moderator

Re: [GMCnet] Alternator Questions [message #139691 is a reply to message #139689]

Wed, 17 August 2011 19:42

larry.whisler

Messages: 356
Registered: August 2005

Karma: 8

Senior Member

I think that clean and tight fittings would also apply to the
diode trio. And that is what caused it to fail. Two of the studs from the rectifier were completly corroded. And those were the ones that failed ( melted ).

I replaced the Voltage Regulator and installed the alternator today. Its now working fine. Output volts at both the bat terminal, isolator, and battery are 14.7 when running.

I am not familiar with the workings of the VR and how it would fail. It seems to me that either the VR failed and melted the diodes & recifier or the diodes/recifier failed and ruined the VR.

In hindsight, I should have replaced all of these components when I had it out. Could have saved myself a lot of work and running back to the auto parts store.

Lession learned for the future.

I am seriously considering rerunning the BAT connection wire to the isolator with 8 gauge. IIRC the OEM wire is 10, especially since I have upgraded to the 100 amp from the 80 OEM.

Was 10 gauge wire used on the 78 models that utilized the 145 amp alternator?

larry whisler

Report message to a moderator

Re: [GMCnet] Alternator Questions [message #139693 is a reply to message #139690]

Wed, 17 August 2011 19:47

Ken Henderson

Messages: 8726
Registered: March 2004
Location: Americus, GA

Karma: 9

Senior Member

That's what I was about to report, Emery. The internal connection is a ring
terminal to stud connection; there is not a through-bolt soldered/welded to
the stator wiring, which would eliminate an internal loose connection.

Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com

On Wed, Aug 17, 2011 at 8:31 PM, Emery Stora <emerystora@mac.com> wrote:

> >
> I had an alternator fail at that same insulator BUT it was the internal
> connection that was loose and burned. NOT the outside connection that I had
> any control over.
>
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist

Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach

Report message to a moderator

Re: [GMCnet] Alternator Questions [message #139698 is a reply to message #139689]

Wed, 17 August 2011 20:18

C Boyd

Messages: 2629
Registered: April 2006

Karma: 18

Senior Member

[quote title=Robert Mueller wrote on Wed, 17 August 2011 20:22]Ken,

I agree with the requirement about the clean and tight connections, however,
IIRC in my case it was tight. I don't remember checking the cleanliness but
removing, cleaning, putting some of grease that used to resist corrosion and
then tightening it just went on my list of TTD when I get back.

Chuck, do you remember if it was tight?

Regards,
Rob M.

Rob: (SIR): IIRC there was a nut that tightened the stud and it wasn`t really tight. The wire to it was tight. It looked like it got hot from the inside.

C. Boyd
76 Crestmont
East Tennessee

Report message to a moderator

Re: [GMCnet] Alternator Questions [message #139700 is a reply to message #139698]

Wed, 17 August 2011 20:22

C Boyd

Messages: 2629
Registered: April 2006

Karma: 18

Senior Member

[quote title=C Boyd wrote on Wed, 17 August 2011 21:18]

Robert Mueller wrote on Wed, 17 August 2011 20:22

Ken,

I agree with the requirement about the clean and tight connections, however,
IIRC in my case it was tight. I don't remember checking the cleanliness but
removing, cleaning, putting some of grease that used to resist corrosion and
then tightening it just went on my list of TTD when I get back.

Chuck, do you remember if it was tight?

Regards,
Rob M.

Rob: (SIR): IIRC there was a nut that tightened the stud and it wasn`t really tight. The wire to it was tight. It looked like it got hot from the inside.

Yes we made sure the new one was tight. You were insistant about it, don`t you member?

C. Boyd
76 Crestmont
East Tennessee

Report message to a moderator

Pages (2): [1 2 › »]

Previous Topic:	Gmc mh on lingo game show
Next Topic:	Cooling System Update Need a Little Help

Goto Forum:

-=] Back to Top [=-

Current Time: Mon Sep 30 12:30:45 CDT 2024

Total time taken to generate the page: 0.01109 seconds