Home » Public Forums » GMCnet » Chassis battery side diagnosis
| Chassis battery side diagnosis [message #204746] |
Mon, 15 April 2013 15:12  |
Don A
Messages: 895
Registered: October 2008
Location: Dallas, TX
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Recently there have been some great guides for diagnoising the house side electric problems. What about the chassis side?
Just driving down the road, enjoying the beautiful Spring ride and the motor looses power and quits. No bangs or noise, no alarm from the volt meter - no nothing. And then when I got stopped, still nothing when I tried to start, no solenoid click. When I push the boost button it fires right up and runs fine until I let go. So it isn't the module in the HEI distributor. The neutral safety switch shouldn't have killed the engine. Does the NSS come into play when you try to start off the house battery? Took the alternator in for a test and they say it is ok. Actually said it was a heavy duty one for a Cad more than an Olds and in fine condition.  yea I guess. So now what, have to look for some kind of possible short that killed the alt output and let it run on the battery until it went down? Wasn't a loose cable at the alt as it was a bear to get the APC loose to get it out.
I know, just check one thing at a time. At least it is not the house side with a zillion added on, undocumented circuits.
Any ideas where to start? Thanks
Don Adams Dallas, TX
'76 26' Glenbrook, '90 Sidekick
rebuilt by R Archer, powered by J Bounds, Koba
[IMG]http://www.gmcmhphotos.com/photos/data/6109/G2.jpg[/IMG]
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| Re: [GMCnet] Chassis battery side diagnosis [message #204749 is a reply to message #204746] |
Mon, 15 April 2013 15:28  |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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sorry this is not clear
but
I will clean it up later.
this is a way to check / rewire your engine battery for this problem
http://www.gmcmhphotos.com/photos/g5493-gmc-cranking-improve-for-free.html
let me know if you have questions :>)
gene
On Mon, Apr 15, 2013 at 1:12 PM, Don Adams <dj.adams@att.net> wrote:
>
>
>
> Recently there have been some great guides for diagnoising the house side
> electric problems. What about the chassis side?
>
> Just driving down the road, enjoying the beautiful Spring ride and the
> motor looses power and quits. No bangs or noise, no alarm from the volt
> meter - no nothing. And then when I got stopped, still nothing when I
> tried to start, no solenoid click. When I push the boost button it fires
> right up and runs fine until I let go. So it isn't the module in the HEI
> distributor. The neutral safety switch shouldn't have killed the engine.
> Does the NSS come into play when you try to start off the house battery?
> Took the alternator in for a test and they say it is ok. Actually said it
> was a heavy duty one for a Cad more than an Olds and in fine condition. :)
> yea I guess. So now what, have to look for some kind of possible short
> that killed the alt output and let it run on the battery until it went
> down? Wasn't a loose cable at the alt as it was a bear to get the APC
> loose to get it out.
>
> I know, just check one thing at a time. At least it is not the house side
> with a zillion added on, undocumented circuits.
>
> Any ideas where to start? Thanks
>
> --
> Don Adams Dallas, TX
> '76 26' Glenbrook, '90 Sidekick
> rebuilt by R Archer, powered by J Bounds, Koba
>
> _______________________________________________
> 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
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| Re: [GMCnet] Chassis battery side diagnosis [message #204750 is a reply to message #204749] |
Mon, 15 April 2013 15:29 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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be sure to read all the slides
gene
On Mon, Apr 15, 2013 at 1:28 PM, gene Fisher <mr.erfisher@gmail.com> wrote:
> sorry this is not clear
> but
> I will clean it up later.
> this is a way to check / rewire your engine battery for this problem
> http://www.gmcmhphotos.com/photos/g5493-gmc-cranking-improve-for-free.html
>
> let me know if you have questions :>)
>
> gene
>
>
>
> On Mon, Apr 15, 2013 at 1:12 PM, Don Adams <dj.adams@att.net> wrote:
>
>>
>>
>>
>> Recently there have been some great guides for diagnoising the house side
>> electric problems. What about the chassis side?
>>
>> Just driving down the road, enjoying the beautiful Spring ride and the
>> motor looses power and quits. No bangs or noise, no alarm from the volt
>> meter - no nothing. And then when I got stopped, still nothing when I
>> tried to start, no solenoid click. When I push the boost button it fires
>> right up and runs fine until I let go. So it isn't the module in the HEI
>> distributor. The neutral safety switch shouldn't have killed the engine.
>> Does the NSS come into play when you try to start off the house battery?
>> Took the alternator in for a test and they say it is ok. Actually said it
>> was a heavy duty one for a Cad more than an Olds and in fine condition. :)
>> yea I guess. So now what, have to look for some kind of possible short
>> that killed the alt output and let it run on the battery until it went
>> down? Wasn't a loose cable at the alt as it was a bear to get the APC
>> loose to get it out.
>>
>> I know, just check one thing at a time. At least it is not the house
>> side with a zillion added on, undocumented circuits.
>>
>> Any ideas where to start? Thanks
>>
>> --
>> Don Adams Dallas, TX
>> '76 26' Glenbrook, '90 Sidekick
>> rebuilt by R Archer, powered by J Bounds, Koba
>>
>> _______________________________________________
>> 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
--
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
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| Re: [GMCnet] Chassis battery side diagnosis [message #204753 is a reply to message #204750] |
Mon, 15 April 2013 15:41 |
Don A
Messages: 895
Registered: October 2008
Location: Dallas, TX
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WOW Gene, you are Johnny on the spot!
McD doesn't make any profit off you.
Thanks very much, I will study that.
Upon review again, most all of that great idea has been done.
Most of the time the starter spins strong and motor starts fine.
Problem now is apparently that when running no juice is going to the HEI or to the battery, but the alternator checks out ok. Unless there is an intermetant problem with the alternator regulator they didn't find. And this was an experienced rebuild shop, not a counter parts pusher.
Thanks
Don Adams Dallas, TX
'76 26' Glenbrook, '90 Sidekick
rebuilt by R Archer, powered by J Bounds, Koba
[IMG]http://www.gmcmhphotos.com/photos/data/6109/G2.jpg[/IMG]
[Updated on: Mon, 15 April 2013 16:02] Report message to a moderator |
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| Re: Chassis battery side diagnosis [message #204754 is a reply to message #204746] |
Mon, 15 April 2013 16:23 |
chasingsummer
Messages: 434
Registered: May 2011
Location: asheboro, nc
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soulnds to me like the battery isolator, side to engine battery opened.
But I would suspect with out reading Genes post, there may be more to it. Or atleast more things worth checking.
brian
asheboro, nc
75 eleganza, 74 build
119k miles and counting,
DOG HOUSE
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| Re: Chassis battery side diagnosis [message #204758 is a reply to message #204754] |
Mon, 15 April 2013 17:02 |
Don A
Messages: 895
Registered: October 2008
Location: Dallas, TX
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Thanks Brian. I cleaned the isolator up recently and it checked fine, but haven't checked it after this problem, duh.
Don Adams Dallas, TX
'76 26' Glenbrook, '90 Sidekick
rebuilt by R Archer, powered by J Bounds, Koba
[IMG]http://www.gmcmhphotos.com/photos/data/6109/G2.jpg[/IMG]
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| Re: Chassis battery side diagnosis [message #204772 is a reply to message #204746] |
Mon, 15 April 2013 19:48 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Am I understanding that the engine battery is dead?
Let's summarize what is happening.
1. The engine runs off of the alternator, not the battery.
2. The engine starts off of the battery.
3. The battery is charged off of the alternator to make it ready for the next time to start.
From your description item #1 is not happening
From your description item #2 is not happening but when using the house battery (boost mode) it does work so the starter and the ignition and the neutral safety switch are all OK.
When you answer the question in the first sentence we will determine if item #3 is failing.
This really sounds like a bad isolator but if it is bad (open on the engine side) the house side voltage should go way high due to the missing reference voltage feeding back to the alternator. I cannot tell this until you answer the first question.
Yes, it also could be a bad alternator or any of the associated wiring.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Chassis battery side diagnosis [message #204794 is a reply to message #204772] |
Tue, 16 April 2013 09:07 |
Don A
Messages: 895
Registered: October 2008
Location: Dallas, TX
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Right Dan, mostly I'm cleaning black paint off everything. And with multiple connections at most terminals trying to be very careful they go back in right place.
and Ken, I ass u me'd the battery was down because it just quit running and no response when the key turned. When I later put it on the charger, big charge for several hours. I didn't check the voltage or electrolyte. 
I understand the engine runs off the alternator, not battery. But when it died, again I ass u me'd the alt failed and it ran until the battery drained.
But the alt checked out good. So today I checked the isolater. Pulled the alt in wire and checked for voltage backwards from both batteries. nada. Then I pulled the wires to each battery, stuck the wire from the now ok engine battery on the alt in. And 12v out on each battery terminal!
So no apparant prob with the alt, the isolator or the battery - although it may be short lived now.
Great except it quit running! later today I'll rehang the alt
and give it a try. will have to try to figure out if the alt is putting out or if it is running off the battery until it dies again.
Thanks
Don Adams Dallas, TX
'76 26' Glenbrook, '90 Sidekick
rebuilt by R Archer, powered by J Bounds, Koba
[IMG]http://www.gmcmhphotos.com/photos/data/6109/G2.jpg[/IMG]
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| Re: Chassis battery side diagnosis [message #204819 is a reply to message #204809] |
Tue, 16 April 2013 13:38 |
Don A
Messages: 895
Registered: October 2008
Location: Dallas, TX
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John I use my several meters all the time. Only guessing is what to check next.
Don Adams Dallas, TX
'76 26' Glenbrook, '90 Sidekick
rebuilt by R Archer, powered by J Bounds, Koba
[IMG]http://www.gmcmhphotos.com/photos/data/6109/G2.jpg[/IMG]
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| Re: Chassis battery side diagnosis [message #204821 is a reply to message #204746] |
Tue, 16 April 2013 13:52 |
bwevers
Messages: 597
Registered: October 2010
Location: San Jose
Karma: 5
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You said it started up after pressing the boost switch.
My guess is that it's either a loose or corroded terminal on the
boost relay or a bad engine battery cable.
Regards,
Bill
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
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| Re: Chassis battery side diagnosis [message #204843 is a reply to message #204794] |
Tue, 16 April 2013 15:53 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| Don A wrote on Tue, 16 April 2013 09:07 |
Right Dan, mostly I'm cleaning black paint off everything. And with multiple connections at most terminals trying to be very careful they go back in right place.
and Ken, I ass u me'd the battery was down because it just quit running and no response when the key turned. When I later put it on the charger, big charge for several hours. I didn't check the voltage or electrolyte.
I understand the engine runs off the alternator, not battery. But when it died, again I ass u me'd the alt failed and it ran until the battery drained.
But the alt checked out good. So today I checked the isolater. Pulled the alt in wire and checked for voltage backwards from both batteries. nada. Then I pulled the wires to each battery, stuck the wire from the now ok engine battery on the alt in. And 12v out on each battery terminal!
So no apparant prob with the alt, the isolator or the battery - although it may be short lived now.
Great except it quit running! later today I'll rehang the alt
and give it a try. will have to try to figure out if the alt is putting out or if it is running off the battery until it dies again.
Thanks
|
From your answer it sure sounds like a bad isolator or alternator.
With both batteries charged, start the engine and let it idle. Read the voltage on the center terminal of the isolator. You can use the aluminum plate that the isolator is mounted on for ground. Now read the voltage in the top and bottom terminals to to the same ground.
You approximate readings should be:
center terminal 14.7 volts
top terminal 14.0 volts
Bottom terminal 14.0 volts
If you get the above (approximate) readings, then the alternator and isolator are good. If not, then let us know what you are reading and we will go from there.
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Chassis battery side diagnosis [message #204856 is a reply to message #204746] |
Tue, 16 April 2013 17:37 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Hopefully Kens isolator test passes. How old is the engine battery? Modern batteries fail in strange ways. . If the isolator test is a pass work your way out and meter at actual batteries.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Chassis battery side diagnosis [message #204857 is a reply to message #204843] |
Tue, 16 April 2013 17:40 |
Don A
Messages: 895
Registered: October 2008
Location: Dallas, TX
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Well, all's well that ends.
And thanks to everyone that had a comment.
Got the alternator back in (sure wish I could do that as quickly and easy as Matt) Fired it up and it sounds great, strong as ever. voltage at isolator center pin 15.2 !, 14,4 each outside, on two different HF meters. Nothing changed except the engine battery and the alternator each out and back in. All the connections had been previously shined and went back exactly the same way they came apart. Still too big a jungle to risk changing anything. Nothing loose or problematic observed. The APC connectors aren't grody but I want to get something to get in there and shine them.
Ken Thanks for your steps, any thoughts of any thing else to watch? Seems good to go except for the nagging feeling that something intermitant is waiting happen again.
Don Adams Dallas, TX
'76 26' Glenbrook, '90 Sidekick
rebuilt by R Archer, powered by J Bounds, Koba
[IMG]http://www.gmcmhphotos.com/photos/data/6109/G2.jpg[/IMG]
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| Re: Chassis battery side diagnosis [message #204858 is a reply to message #204856] |
Tue, 16 April 2013 17:44 |
Don A
Messages: 895
Registered: October 2008
Location: Dallas, TX
Karma: 0
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| JohnL455 wrote on Tue, 16 April 2013 17:37 |
Hopefully Kens isolator test passes. How old is the engine battery? Modern batteries fail in strange ways. . If the isolator test is a pass work your way out and meter at actual batteries.
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Engine battery about a year old, plenty strong. Drained down when the problem occured and charged right back up on shop charger. Both batteries holding an 12.6 volts for more than a week.
Don Adams Dallas, TX
'76 26' Glenbrook, '90 Sidekick
rebuilt by R Archer, powered by J Bounds, Koba
[IMG]http://www.gmcmhphotos.com/photos/data/6109/G2.jpg[/IMG]
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| Re: Chassis battery side diagnosis [message #204876 is a reply to message #204857] |
Tue, 16 April 2013 20:03 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Since every thing is working correctly now, about the only thing you can do is monitor the engine / chassis side voltage while you are driving. If you do not have a voltmeter in your dash, you can buy a cigarette lighter plug in type cheap at Harbor Freight or Walmart (near the car batteries for sale).
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Chassis battery side diagnosis [message #204913 is a reply to message #204876] |
Wed, 17 April 2013 08:58 |
Don A
Messages: 895
Registered: October 2008
Location: Dallas, TX
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Thanks Ken, I will monitor the voltage. Maybe further down the line, after the isolator? You must be right that the isolator is failing. I was busy getting off the road and must not have looked at the digipanel. A failed alternator seemed the logical problem. So I didn't check voltages after the fact, lesson learned.
But the digipanel alarm didn't go off, one of the things I don't understand about this incident. When I lost the alternator belt after picking up the coach from Arch, the digipanel let me know before any symptoms. Does this mean the juice for the coil and distributor comes after the isolator? That doesn't sound very good, time to study the charts.
And Thanks Dan, need to get a combiner right away. That's the first I have heard of combiner issues, intermittent elec issues are a bear.
And Thanks again to Brian for the early suggestion to check the isolator.
You guys have made me feel confident in the coach again.
Don Adams Dallas, TX
'76 26' Glenbrook, '90 Sidekick
rebuilt by R Archer, powered by J Bounds, Koba
[IMG]http://www.gmcmhphotos.com/photos/data/6109/G2.jpg[/IMG]
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| Re: Chassis battery side diagnosis [message #204928 is a reply to message #204913] |
Wed, 17 April 2013 09:51 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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It all depends on where the digi-panel is sampling the voltage. I would sample the voltage AFTER the isolator. That is where every thing is attached in the chassis system. That is why I suggested the cigarette lighter plug in meter. I did not know or remember that you had a digipanel. You can easily use the Digipanel if it is wired correctly.
If it helps, just consider the isolator as part of the alternator circuit.
Note: The alternator does this same thing by sampling the output voltage for it's regulator AFTER the isolator.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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