Home » Public Forums » GMCnet » No AC current from Onan, Ideas?
| No AC current from Onan, Ideas? [message #205541] |
Mon, 22 April 2013 19:02  |
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Well I've been outta circulation for a while but I'm back this time with a problem unfortunately. my Onan which has been pretty much old faithful finally quit putting out AC power all of a sudden. the engine runs like a top as always, but wondering why the AC took a dump. what is the general consensus for the most likely issue so I can start there first?
Shan
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: [GMCnet] No AC current from Onan, Ideas? [message #205542 is a reply to message #205541] |
Mon, 22 April 2013 19:05  |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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Senior Member |
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Same thing happened to me a few years ago. It was a simple fix, though it sounds mysterious - the bridge rectifier died. They are cheap, and Jim K probably has them by the dozen.
<http://www.appliedgmc.com/prod.itml/icOid/974>
Larry Davick
Fremont, California
A Mystery Machine
'76 (ish) Palm Beach
----- Original Message -----
From: "Shan Rose" <defconfx@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Monday, April 22, 2013 5:02:35 PM
Subject: [GMCnet] No AC current from Onan, Ideas?
Well I've been outta circulation for a while but I'm back this time with a problem unfortunately. my Onan which has been pretty much old faithful finally quit putting out AC power all of a sudden. the engine runs like a top as always, but wondering why the AC took a dump. what is the general consensus for the most likely issue so I can start there first?
Shan
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: No AC current from Onan, Ideas? [message #205583 is a reply to message #205541] |
Mon, 22 April 2013 22:47 |
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Gentlemen thanks again! I think the BR is probably the issue due to the water heater being left on accidentally the last time the genny was ran at length. Would explain why one day it ran fine and the next not even though the engine runs like a swiss watch since my pertonix conversion 2 years ago. Ironically my little suitcase gen took a dump at the same time, with a fried stator winding! Hmmm as far as I know the north Koreans havent EMPed us so kinda funny to have 2 plants fail at the same time...
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: [GMCnet] No AC current from Onan, Ideas? [message #205601 is a reply to message #205583] |
Tue, 23 April 2013 07:48 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Shan,
Bridge rectifier failures are most commonly attributed to shutting down the
generator with the air conditioner(s) running. That's certainly not the
only cause though.
I use bridge rectifiers in the wiring harness for my electric wipers to
"fool" the motor into thinking I use a DPDT switch. Although I need <10A
and <25 PIV ratings, in the past I've bought only those rated at 25-35A @
400-600 PIV so they were equally useful for Onans. Lately the prices have
gone up so much I no longer do that, but I still recommend those higher
ratings for Onans.
Ken H.
On Mon, Apr 22, 2013 at 11:47 PM, Shan Rose wrote:
>
>
> Gentlemen thanks again! I think the BR is probably the issue due to the
> water heater being left on accidentally the last time the genny was ran at
> length. Would explain why one day it ran fine and the next not even though
> the engine runs like a swiss watch since my pertonix conversion 2 years
> ago. Ironically my little suitcase gen took a dump at the same time, with a
> fried stator winding! Hmmm as far as I know the north Koreans havent EMPed
> us so kinda funny to have 2 plants fail at the same time...
> _______________________________________________
>
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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: No AC current from Onan, Ideas? [message #205796 is a reply to message #205541] |
Thu, 25 April 2013 03:13 |
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Well today I got a BR and now I have an issue. The old BR does not have any terminal markings. And I have 3 white and one black wore coming out of the socket the BR plugs into, so is the black a hot or negative wire? I checked the "Bible" and no mention of color coding of the wires! Ugh this os not major it it is annoying...
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: No AC current from Onan, Ideas? [message #205798 is a reply to message #205796] |
Thu, 25 April 2013 06:35 |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Senior Member |
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BR has four leads. 2 are A/C input and 2 are D/C out. I know speaking the obvious. The BR should be marked, generally with a curved line indicating A/C in and a Straight line indicating DC out. They will be on opposite corner connections of the flat cube. The cubes sold now have to have one of the leads twisted 90 degrees to align with the Onan connector. The older style directly plugging in is difficult to find.
Hope this helps.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: [GMCnet] No AC current from Onan, Ideas? [message #205801 is a reply to message #205798] |
Thu, 25 April 2013 07:03 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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I just looked at five I have in stock, all different ones. In every case, the positive lead or lug is at the corner which is shaved at an angle. For the flat square ones, the minus is diagonally opposite the plus, the AC inputs are the other diagonal.
For the flat inline with four leads, the shaved end is the pl;us, the opposite end is the minus, and the two leads in the middle are the AC inputs.
--johnny
'76 23' transmode norris
'76 palm beach
From: Thomas Phipps <tph1pp5@yahoo.com>
To: gmclist@temp.gmcnet.org
Sent: Thursday, April 25, 2013 7:35 AM
Subject: Re: [GMCnet] No AC current from Onan, Ideas?
BR has four leads. 2 are A/C input and 2 are D/C out. I know speaking the obvious. The BR should be marked, generally with a curved line indicating A/C in and a Straight line indicating DC out. They will be on opposite corner connections of the flat cube. The cubes sold now have to have one of the leads twisted 90 degrees to align with the Onan connector. The older style directly plugging in is difficult to find.
Hope this helps.
Tom, MS II
--
1975 GMC Avion, under forever re-construction
Vicksburg, MS. 3.7 miles from I-20
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: No AC current from Onan, Ideas? [message #205847 is a reply to message #205541] |
Thu, 25 April 2013 13:28 |
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I think it was a bit misunderstood as to what I meant. My new BR is clearly marked. I just need to know which wires on the connector is the hot and cold. I have 1 black wire and 3 white ones which is what is making this hard. The manual also doesnt say anything about the wiring color codes :/
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: [GMCnet] No AC current from Onan, Ideas? [message #205850 is a reply to message #205847] |
Thu, 25 April 2013 13:56 |
Jim Miller
Messages: 501
Registered: March 2008
Karma: 10
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Senior Member |
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On Apr 25, 2013, at 2:28 PM, Shan Rose wrote:
> I think it was a bit misunderstood as to what I meant. My new BR is clearly marked. I just need to know which wires on the connector is the hot and cold. I have 1 black wire and 3 white ones which is what is making this hard. The manual also doesnt say anything about the wiring color codes :/
You can't go by colors on the wires. Double check the old BR and there should be a red dot or a + near one of the lugs. That's DC+ and then diagonally from it across is DC-. The leftover two are AC.
By looking in the lower bell housing opening you should be able to see the field wires going through insulated splices and then on to the windings. They are usually twisted together. As a double check you can measure 39 ohms across them with an ohmmeter.
The compounding reactor wires go to the AC side of the BR and the field winding wires to the DC.
--Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
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Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
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| Re: No AC current from Onan, Ideas? [message #205942 is a reply to message #205541] |
Fri, 26 April 2013 00:54 |
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Well I got the new BR in after modifying the connectors on it, and well still no juice! So guess im gonna have to break out the DMM and get some testing. One thing I wondered about is the brushes, my onan got heavy use from time to time, perhaps the brushes are well worn? Is there a source for new ones should this be the case?
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: [GMCnet] No AC current from Onan, Ideas? [message #205944 is a reply to message #205942] |
Fri, 26 April 2013 01:11 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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You might need to test you field and the armature.
Should you need either, we might have a highly priced new one in stock or used.
On Thu, Apr 25, 2013 at 10:54 PM, Shan Rose <defconfx@gmail.com> wrote:
>
>
> Well I got the new BR in after modifying the connectors on it, and well still no juice! So guess im gonna have to break out the DMM and get some testing. One thing I wondered about is the brushes, my onan got heavy use from time to time, perhaps the brushes are well worn? Is there a source for new ones should this be the case?
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--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] No AC current from Onan, Ideas? [message #205969 is a reply to message #205942] |
Fri, 26 April 2013 08:42 |
Jim Miller
Messages: 501
Registered: March 2008
Karma: 10
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Senior Member |
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On Apr 26, 2013, at 1:54 AM, Shan Rose wrote:
> Well I got the new BR in after modifying the connectors on it, and well still no juice! So guess im gonna have to break out the DMM and get some testing. One thing I wondered about is the brushes, my onan got heavy use from time to time, perhaps the brushes are well worn? Is there a source for new ones should this be the case?
Test the field winding first - it should be between 37 and 39 ohms. The field windings, being made of aluminum wire and being 40 years old, are a common failure item.
When I am faced with any Onan with no AC output the first thing I check - before bridge rectifier, brushes or anything else - is the field winding. Out of perhaps a dozen Onans I've personally examined in my GMC career I've seen at least 7 with busted fields.
It could be that you broke a field wire during your BR change - the windings are solid aluminum wire and they break from fatigue very easily.
--Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
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Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
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| Re: No AC current from Onan, Ideas? [message #205973 is a reply to message #205541] |
Fri, 26 April 2013 09:16 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Are you sure the leads are on the right BR terminals? Of the possible permutations the + - need to be correct. AC should then be the last two and go either way. Obvious but worth checking.
John Lebetski
Woodstock, IL
77 Eleganza II
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