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| One electrical problem leads to another. [message #96762] |
Sun, 22 August 2010 07:43  |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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Senior Member |
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Yesterday I decided to change the long clumsy 50Amp cord to a more manageable 4ft cord and make the existing cord into a 50Amp extension cord. I had bought a 4ft stove power cord for the job.
I removed the old cord and while hooking up the new cord I noticed the ground wires inside the breaker panel were almost touching one of the line lugs (couple thicknesses of paper clearance). Its a wonder the vibration driving down the road with the Generator going for the AC, didn't cause a short.
A PO had replaced the generator socket with a surface mount receptacle that was hard to get at so I decided to install a surface mount. When I removed the surface mount receptacle, the connecting wires to it came out too! There were 2 wire and 2 black wires about 8" long that had been crimped connected down inside the flex conduit. There was no way I could work though the receptacle hole in the side of the exterior electrical compartment so I removed the access cover behind the breaker panel and all the wiring that goes with it.
After removing the box from the BX type cable, the two wires would only come out about 1" beyond the conduit. Geez! how cheap can you get with wire!... another 6 or 8" please! and both are Black wires so now I have to figure out which is hot and which is neutral/ground. I also checked to see if I could cut back the flex conduit to expose more wire, but there was barely enough as it was.
So I look at pulling new wires though the flex conduit. With all the tight bends I knew that would be a major and near impossible job with heavy cables. So I elected to fix it as it was, crimp these short pieces back on, solder and heat-shrink them. But now I have figure out which wire is which. They are too short to separate and start the genny, so I measure resistance to ground and find one is 0 ohms and the other is 7ohms.. Ok the 0 ohm wire has to be the neutral/ground. I crimp the wires back on and double shrink tube them.
Paula strugled to hold the box in place from the outside while I tried to get the socked mounted in the electric compartment from the ouside.. after alot of cussing I got it back in. Started the genny and tested the voltage at the new socket.. all looks good so I plug in the new short cord and the generator feels a bit of load.. Hmm I think.. I was sure the AC was off.. maybe the water heater is ON. Then I hear the load come off the genny. Inside there is no power, unplug and check at the genny socket, no power.... pull open the Onan and I see the breaker is tripped.
I reset the breaker and power is back at the socket... so I check for voltage between the body and ground... Damn.. I have the Hot and Neutral reversed! So I shut down the genny again and remeasure my resistances to ground... same what I assumed was neutral/Ground has 0 ohms and what I figured was Hot is 7ohms. But I obviously have them reversed! How can the neutral/Ground which is grounded directly read 7 ohms while the Hot which goes through the reactor and armature coils read 0!
Well I can't redo the splices at the socket end to keep the proper colour code, but wait... both power wires at the Onan are White!! Who wired this thing!! there is a junction box at the back of the Onan box where the two White wires from the Onan join the 2 black wires going to the socket... it would be nice if would have used a Black (Hot) and White Neutral all the way though.
I wanted to ohmmeter both wires from the Onan right through to the socket to be sure they were isolated and one was not grounded in that junction box so I opened both connections. The neutral is just 2 lugs bolted together and taped. They appear to be isolated.
I had no other choice short of pulling out the cabinets etc, to reverse my wiring at the new socket. I used a permanent marker to write a warning to the next guy about the reversed wire colours. So after more cussing to get the socket back in the box its now back together again and ready for a test.... BUT.... when I opened that neutral connection at the back of the Onan, the small #10 bolt dropped from by greasy fingers. I can't find it anywhere so I have to assume it fell through the plastic covers at the back of the genny and inside. I'm afraid to start the Onan until I find this little bolt as it might damage the generator itself... so back to that today.
I really hope I don't have to pull the Onan out to find that little screw as it doesn't look like a fun job.
And so another little GMC job becomes another BIG GMC job!
The saga contines......
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
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| Re: [GMCnet] One electrical problem leads to another. [message #96763 is a reply to message #96762] |
Sun, 22 August 2010 07:59  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Bruce,
Too bad about "one of THOSE days"! Sounds like me last week when I dropped
the #7 intake pushrod into the Cad500. Couldn't find that thing for nothin'
with a magnet. Finally borrow a bore scope and found it standing right
beside where it belonged so that a magnet could lift it right out. Then
when being VERY careful with #1, did the same thing again. That time I knew
where to probe. :-)
The Cad's all back together now & still runs. You'll fix yours too.
Ken H.
On Sun, Aug 22, 2010 at 8:43 AM, Bruce Hislop <bruce@perthcomm.com> wrote:
> ...
I really hope I don't have to pull the Onan out to find that little screw as
> it doesn't look like a fun job.
>
> And so another little GMC job becomes another BIG GMC job!
>
> The saga contines......
>
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] One electrical problem leads to another. [message #96764 is a reply to message #96762] |
Sun, 22 August 2010 08:00 |
Charles
Messages: 455
Registered: January 2004
Karma: 0
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Senior Member |
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Bruce,
And I thought I was the only one that knows Murphy.
I think ( should put think in quotations) both black wires
on my coach are hot and the two whites are neutral.
One of the electrical wizards should come in here and
help us out. If I remember correctly the two black wires go to
the two side prongs on the 50 amp plug and the two whites
go to the top and bottom prongs. Again I think this separates
the 50 amp service into two separate 120 volt circuits.
HELP!!!!!!!!!!!!!!!!!!!
Charles
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Charles Wersal
Duncanville, Texas
26 foot 1975 Glenbrook
Pandora's Box
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| Re: [GMCnet] One electrical problem leads to another. [message #96792 is a reply to message #96771] |
Sun, 22 August 2010 10:58 |
gmcrv1
Messages: 839
Registered: August 2007
Location: Memphis
Karma: -1
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Senior Member |
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Bruce,
Glad you found that screw. Dropped screws, nuts washers etc. are really not
good to have floating around inside the genset area. The biggest problem
they pose is getting caught in between two opposite polarity wires or a hot
wire or terminal and then they short to ground. You know it's bad and only
the sound that the spark makes and the amount of smoke it releases from the
cable or device tells you how severe the damage is. A little smoke - could
be a temporary interruption or throw a breaker. A lot of smoke - you may
have welded something that really didn't need welding!
Good Luck,
Tom Eclert N2VWN
73 Glacier
Oakland, TN
On Sun, Aug 22, 2010 at 9:06 AM, Bruce Hislop <bruce@perthcomm.com> wrote:
>
>
> I can't believe it! I found the elusive screw after 5 mins of searching
> this morning!
>
> Now a another problem.... before connecting the neutral wires with the
> elusive screw above, I measured out the resistance of the neutral wire to
> the new socket.. I get about 60ohms! somewhere, likely in that junction box
> is a bad connection. I'm thinking its been getting its neutral return
> through the body/frame ground onto the frame ground of the Onan.
>
> So it looks like I'll have to pull it anyway. Need to get a lift to remove
> it!
>
> Yes I do know Murphy's law quite well.
>
> Anyone know Cole's Law? (thinly slice cabbage! :lol:)
>
>
> --
> Bruce Hislop,
> S. Ontario Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI and ESC.
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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List Information and Subscription Options:
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| Re: [GMCnet] One electrical problem leads to another. [message #96793 is a reply to message #96792] |
Sun, 22 August 2010 11:06 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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If I remember my basic electricity, one ampere of current flow is something
like One billion, billion electrons per second. Think about a 6K ONAN with a
dead short across the output leads. Kinda encourages one to find that lost
bolt before starting the critter up, not after it fuses everything into a
smouldering, stinking pile of useless junk.
Jim Hupy
Salem, Or
78 Royale 403
On Sun, Aug 22, 2010 at 8:58 AM, Tom Eckert <gmcrv1@gmail.com> wrote:
> Bruce,
>
> Glad you found that screw. Dropped screws, nuts washers etc. are really
> not
> good to have floating around inside the genset area. The biggest problem
> they pose is getting caught in between two opposite polarity wires or a hot
> wire or terminal and then they short to ground. You know it's bad and only
> the sound that the spark makes and the amount of smoke it releases from the
> cable or device tells you how severe the damage is. A little smoke -
> could
> be a temporary interruption or throw a breaker. A lot of smoke - you may
> have welded something that really didn't need welding!
>
> Good Luck,
>
> Tom Eclert N2VWN
> 73 Glacier
> Oakland, TN
>
> On Sun, Aug 22, 2010 at 9:06 AM, Bruce Hislop <bruce@perthcomm.com> wrote:
>
> >
> >
> > I can't believe it! I found the elusive screw after 5 mins of searching
> > this morning!
> >
> > Now a another problem.... before connecting the neutral wires with the
> > elusive screw above, I measured out the resistance of the neutral wire to
> > the new socket.. I get about 60ohms! somewhere, likely in that junction
> box
> > is a bad connection. I'm thinking its been getting its neutral return
> > through the body/frame ground onto the frame ground of the Onan.
> >
> > So it looks like I'll have to pull it anyway. Need to get a lift to
> remove
> > it!
> >
> > Yes I do know Murphy's law quite well.
> >
> > Anyone know Cole's Law? (thinly slice cabbage! :lol:)
> >
> >
> > --
> > Bruce Hislop,
> > S. Ontario Canada
> > 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI and ESC.
> > http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> > _______________________________________________
> > GMCnet mailing list
> > List Information and Subscription Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
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| Re: [GMCnet] One electrical problem leads to another. [message #96795 is a reply to message #96793] |
Sun, 22 August 2010 11:11 |
gmcrv1
Messages: 839
Registered: August 2007
Location: Memphis
Karma: -1
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Senior Member |
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Exactly.
On Sun, Aug 22, 2010 at 11:06 AM, James Hupy <jamesh1296@gmail.com> wrote:
> If I remember my basic electricity, one ampere of current flow is something
> like One billion, billion electrons per second. Think about a 6K ONAN with
> a
> dead short across the output leads. Kinda encourages one to find that lost
> bolt before starting the critter up, not after it fuses everything into a
> smouldering, stinking pile of useless junk.
> Jim Hupy
> Salem, Or
> 78 Royale 403
>
> On Sun, Aug 22, 2010 at 8:58 AM, Tom Eckert <gmcrv1@gmail.com> wrote:
>
> > Bruce,
> >
> > Glad you found that screw. Dropped screws, nuts washers etc. are really
> > not
> > good to have floating around inside the genset area. The biggest problem
> > they pose is getting caught in between two opposite polarity wires or a
> hot
> > wire or terminal and then they short to ground. You know it's bad and
> only
> > the sound that the spark makes and the amount of smoke it releases from
> the
> > cable or device tells you how severe the damage is. A little smoke -
> > could
> > be a temporary interruption or throw a breaker. A lot of smoke - you may
> > have welded something that really didn't need welding!
> >
> > Good Luck,
> >
> > Tom Eclert N2VWN
> > 73 Glacier
> > Oakland, TN
> >
> > On Sun, Aug 22, 2010 at 9:06 AM, Bruce Hislop <bruce@perthcomm.com>
> wrote:
> >
> > >
> > >
> > > I can't believe it! I found the elusive screw after 5 mins of searching
> > > this morning!
> > >
> > > Now a another problem.... before connecting the neutral wires with the
> > > elusive screw above, I measured out the resistance of the neutral wire
> to
> > > the new socket.. I get about 60ohms! somewhere, likely in that junction
> > box
> > > is a bad connection. I'm thinking its been getting its neutral return
> > > through the body/frame ground onto the frame ground of the Onan.
> > >
> > > So it looks like I'll have to pull it anyway. Need to get a lift to
> > remove
> > > it!
> > >
> > > Yes I do know Murphy's law quite well.
> > >
> > > Anyone know Cole's Law? (thinly slice cabbage! :lol:)
> > >
> > >
> > > --
> > > Bruce Hislop,
> > > S. Ontario Canada
> > > 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI and ESC.
> > > http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> > > _______________________________________________
> > > GMCnet mailing list
> > > List Information and Subscription Options:
> > > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> > >
> > _______________________________________________
> > GMCnet mailing list
> > List Information and Subscription Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: One electrical problem leads to another. [message #96796 is a reply to message #96762] |
Sun, 22 August 2010 11:35 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
Karma: 0
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Senior Member |
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| RF_Burns wrote on Sun, 22 August 2010 05:43 |
Yesterday I decided to change the long clumsy 50Amp cord to a more manageable 4ft cord and make the existing cord into a 50Amp extension cord. I had bought a 4ft stove power cord for the job.
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I hate to tell you this, but a range cord is NOT the way to go when shortening the original cord. A range cord has two large hot wires and one smaller neutral wire, I think #10 maximum for the neutral. Because the Onan is a 120 volt device all the current from both the hot wires must return to the Onan via the neutral. The range cord neutral is not large enough for the total 6000 watts the Onan can produce.
If you look at the original 50 amp cord, you will see a full sized #6 wire for both the hots and the neutral. You can cut this down to a shorter size for what you want to do, or build your own cord with a proper sized neutral, which is what I did when I changed mine over.
http://www.gmcmhphotos.com/photos/showgallery.php?cat=3908
Rob Allen
former owner of '76 x-PB
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| Re: One electrical problem leads to another. [message #96903 is a reply to message #96762] |
Mon, 23 August 2010 08:22 |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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Senior Member |
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Good point Rob, I had thought of that and will likely change at some point in the near future.
I only have a single A/C, so between that and making a pot of coffee I think my max current consumption stays under 20amp. I've never had a 50amp service, usually 15amp and sometimes 30.
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
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