Home » Public Forums » GMCnet » Onan trouble shooting (No AC power from gen set)
| Onan trouble shooting [message #343727] |
Mon, 27 May 2019 16:53  |
Ken Shaffer
Messages: 89
Registered: September 2017
Location: Marion Iowa
Karma: -1
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My generator has not been used for at least eight years. I am now trying to get it working. I have been able to get it started and it runs fine but I do not have any AC power inside. Shore power cord is connected to generator plug And switch on top of Onan is on. Any advise on where to start?
6K power drawer.
Ken Shaffer
73 canyon lands
Ken Shaffer
Marion Iowa
73 Canyon Lands, 455, Micro-level, Alum radiator, Alcoa wheels, Lenzi hubs/bearings, Howell EFI/EBL, Rostra Cruise, Custom interior
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| Re: [GMCnet] Onan trouble shooting [message #343734 is a reply to message #343730] |
Mon, 27 May 2019 19:51  |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Did you check your ac breakers to make sure they are on?
Sully
Bellevue wa
On Mon, May 27, 2019 at 4:25 PM Emery Stora via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Take a voltmeter and check to see if you have voltage to both sides of the
> top switch. Report back as to what you find and we’ll give more
> instructions.
>
> Emery Stora
>
>> On May 27, 2019, at 4:53 PM, Ken Shaffer via Gmclist gmclist@list.gmcnet.org> wrote:
>>
>> My generator has not been used for at least eight years. I am now trying
> to get it working. I have been able to get it started and it runs fine but I
>> do not have any AC power inside. Shore power cord is connected to
> generator plug And switch on top of Onan is on. Any advise on where to
> start?
>>
>> 6K power drawer.
>>
>> Ken Shaffer
>> 73 canyon lands
>>
>> --
>> Ken Shaffer
>> Marion Iowa
>> 73 Canyon Lands, 455, Manny Tranny, Custom interior
>>
>>
>> _______________________________________________
>> GMCnet mailing list
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>
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: [GMCnet] Onan trouble shooting [message #343736 is a reply to message #343727] |
Mon, 27 May 2019 20:12 |
Jim Miller
Messages: 501
Registered: March 2008
Karma: 10
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On May 27, 2019, at 5:53 PM, Ken Shaffer via Gmclist wrote:
> My generator has not been used for at least eight years. I am now trying to get it working. I have been able to get it started and it runs fine but I do not have any AC power inside. Shore power cord is connected to generator plug And switch on top of Onan is on. Any advise on where to start?
Our Onans - being a self-exciting design - depend on residual magnetic field in the stator in order to begin the excitation process as the armature starts to turn during engine start. Over time that residual field decays away and given a long enough interval it will no longer be strong enough to start the excitation process and the classic result is “no AC”. Eight years is easily long enough for this to take place.
Check http://www.gmcws.org/Tech/dsimmons/onan_demo/ and see the section called “Loss of Residual Magnetism”.
Do not try anything else until you go through the “Loss of Residual Magnetism” procedure described above. MAKE SURE you label the + and - wires as you take them off the bridge rectifier and MAKE SURE they go back onto the same terminals after you carry out the flashing procedure.
Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
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Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
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| Re: Onan trouble shooting [message #343759 is a reply to message #343727] |
Tue, 28 May 2019 12:55 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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What Mr. Miller said. Report back.
--johnny
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: Onan trouble shooting [message #343769 is a reply to message #343727] |
Tue, 28 May 2019 19:52 |
Ken Shaffer
Messages: 89
Registered: September 2017
Location: Marion Iowa
Karma: -1
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I have 3volts reading on left side of breaker.
I energized the wires that the BR plugs into ... nothing.
Ken
Ken Shaffer
Marion Iowa
73 Canyon Lands, 455, Micro-level, Alum radiator, Alcoa wheels, Lenzi hubs/bearings, Howell EFI/EBL, Rostra Cruise, Custom interior
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| Re: Onan trouble shooting [message #343770 is a reply to message #343769] |
Tue, 28 May 2019 20:05 |
mghamms
Messages: 466
Registered: March 2016
Location: Ware, Massachusetts
Karma: 2
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How about voltage on the right side of the breaker?
Ken Shaffer wrote on Tue, 28 May 2019 19:52I have 3volts reading on left side of breaker.
I energized the wires that the BR plugs into ... nothing.
Ken
1977 Kingsley 455 as stock as it gets except lots of Ragusa parts
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| Re: [GMCnet] Onan trouble shooting [message #343774 is a reply to message #343770] |
Tue, 28 May 2019 22:12 |
Ken Shaffer
Messages: 89
Registered: September 2017
Location: Marion Iowa
Karma: -1
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I couldn’t get anything on the right side. But I didn’t try real hard. I
will re-check that tomorrow. I did pull off the BR and tried to test it. I
was only able to get 2.7 ohms with two terminals and nothing with a
combination of other terminals. My multi meter is not high-quality and I am
pretty inexperienced as well, so I will re-check Everything you have asked
with another tool tomorrow.
On Tue, May 28, 2019 at 8:22 PM Mike Hamm via Gmclist <
gmclist@list.gmcnet.org> wrote:
> How about voltage on the right side of the breaker?
>
> Ken Shaffer wrote on Tue, 28 May 2019 19:52
>> I have 3volts reading on left side of breaker.
>> I energized the wires that the BR plugs into ... nothing.
>>
>> Ken
>
>
> --
> 1977 Kingsley 455 as stock as it gets except lots of Ragusa parts
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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Ken Shaffer
Marion Iowa
73 Canyon Lands, 455, Micro-level, Alum radiator, Alcoa wheels, Lenzi hubs/bearings, Howell EFI/EBL, Rostra Cruise, Custom interior
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| Re: [GMCnet] Onan trouble shooting [message #343778 is a reply to message #343774] |
Wed, 29 May 2019 06:42 |
Jim Miller
Messages: 501
Registered: March 2008
Karma: 10
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The 3VAC reading is the classic indication of “no excitation”. There are only a few things that can cause this:
1. loss of residual magnetism in the field (thus the flashing procedure already described).
2. defective bridge rectifier
3. defective field assembly
4. defective compounding reactor (unlikely)
While you have the bridge out, use your meter to check resistance between the F1 and F2 wires that previously attached to the bridge’s + and - terminals. You should read around 38 ohms.
Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
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Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
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| Re: [GMCnet] Onan trouble shooting [message #343780 is a reply to message #343779] |
Wed, 29 May 2019 07:24 |
Jim Miller
Messages: 501
Registered: March 2008
Karma: 10
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Hi Emery,
He is referring to ohms when testing his bridge rectifier.
—Jim
> On May 29, 2019, at 8:01 AM, Emery Stora via Gmclist wrote:
>
> You don’t want to read ohms. Put the meter on ac volts. You should get 110 to 120 volts on each side of the switch when it’s on.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>
>> On May 28, 2019, at 10:12 PM, Ken Shaffer via Gmclist wrote:
>>
>> I couldn’t get anything on the right side. But I didn’t try real hard. I
>> will re-check that tomorrow. I did pull off the BR and tried to test it. I
>> was only able to get 2.7 ohms with two terminals and nothing with a
>> combination of other terminals. My multi meter is not high-quality and I am
>> pretty inexperienced as well, so I will re-check Everything you have asked
>> with another tool tomorrow.
Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
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Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
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| Re: [GMCnet] Onan trouble shooting [message #343782 is a reply to message #343780] |
Wed, 29 May 2019 08:15 |
Ken Shaffer
Messages: 89
Registered: September 2017
Location: Marion Iowa
Karma: -1
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Correct, I did have my meter on AC when testing the breaker. I also
checked an outlet in my shop first to make sure all was reading correctly.
(got 120) Then I tested breaker and it read 3.
On Wed, May 29, 2019 at 7:24 AM Jim Miller via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Hi Emery,
> He is referring to ohms when testing his bridge rectifier.
> —Jim
>
>> On May 29, 2019, at 8:01 AM, Emery Stora via Gmclist gmclist@list.gmcnet.org> wrote:
>>
>> You don’t want to read ohms. Put the meter on ac volts. You should get
> 110 to 120 volts on each side of the switch when it’s on.
>>
>> Emery Stora
>> 77 Kingsley
>> Frederick, CO
>>
>>> On May 28, 2019, at 10:12 PM, Ken Shaffer via Gmclist gmclist@list.gmcnet.org> wrote:
>>>
>>> I couldn’t get anything on the right side. But I didn’t try real hard. I
>>> will re-check that tomorrow. I did pull off the BR and tried to test
> it. I
>>> was only able to get 2.7 ohms with two terminals and nothing with a
>>> combination of other terminals. My multi meter is not high-quality and
> I am
>>> pretty inexperienced as well, so I will re-check Everything you have
> asked
>>> with another tool tomorrow.
>
>
> Jim Miller
> 1977 Eleganza
> 1977 Royale
> Hamilton, OH
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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Ken Shaffer
Marion Iowa
73 Canyon Lands, 455, Micro-level, Alum radiator, Alcoa wheels, Lenzi hubs/bearings, Howell EFI/EBL, Rostra Cruise, Custom interior
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| Re: [GMCnet] Onan trouble shooting [message #343784 is a reply to message #343778] |
Wed, 29 May 2019 08:45 |
Ken Shaffer
Messages: 89
Registered: September 2017
Location: Marion Iowa
Karma: -1
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Member |
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JIm, I checked the resistance between F1 and F2 wires and got 37.6.
On Wed, May 29, 2019 at 6:42 AM Jim Miller wrote:
> The 3VAC reading is the classic indication of “no excitation”. There are
> only a few things that can cause this:
>
> 1. loss of residual magnetism in the field (thus the flashing procedure
> already described).
> 2. defective bridge rectifier
> 3. defective field assembly
> 4. defective compounding reactor (unlikely)
>
> While you have the bridge out, use your meter to check resistance between
> the F1 and F2 wires that previously attached to the bridge’s + and -
> terminals. You should read around 38 ohms.
>
> Jim Miller
> 1977 Eleganza
> 1977 Royale
> Hamilton, OH
>
>
>
>
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Ken Shaffer
Marion Iowa
73 Canyon Lands, 455, Micro-level, Alum radiator, Alcoa wheels, Lenzi hubs/bearings, Howell EFI/EBL, Rostra Cruise, Custom interior
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| Re: [GMCnet] Onan trouble shooting [message #343785 is a reply to message #343784] |
Wed, 29 May 2019 09:18 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Ken Shaffer wrote on Wed, 29 May 2019 09:45JIm, I checked the resistance between F1 and F2 wires and got 37.6.
Ken,
You got lucky on one.
Your next best hope is the bridge rectifier has gone out. (A very common issue)
I think that the Onan stuff tells how to check it. So do that next.
In simple terms, you should find a diode (that reads low one way and high the other) between each pair of pins.
When it doesn't check out, get a new one.
Good Luck
Matt
On Wed, May 29, 2019 at 6:42 AM Jim Miller wrote:
> The 3VAC reading is the classic indication of "no excitation". There are
> only a few things that can cause this:
>
> 1. loss of residual magnetism in the field (thus the flashing procedure
> already described).
> 2. defective bridge rectifier
> 3. defective field assembly
> 4. defective compounding reactor (unlikely)
>
> While you have the bridge out, use your meter to check resistance between
> the F1 and F2 wires that previously attached to the bridge's + and -
> terminals. You should read around 38 ohms.
>
> Jim Miller
> 1977 Eleganza
> 1977 Royale
> Hamilton, OH
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
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| Re: Onan trouble shooting [message #343790 is a reply to message #343727] |
Wed, 29 May 2019 11:53 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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You are right there. Do the flash procedure and you will probably fix it. Around 38 ohms says the field is good. Flash the thing and see what happens. If flashing does not work, then the next thing is the checking / replacing the diode bridge.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Onan trouble shooting [message #343817 is a reply to message #343727] |
Fri, 31 May 2019 14:18 |
Ken Shaffer
Messages: 89
Registered: September 2017
Location: Marion Iowa
Karma: -1
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Member |
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Just wanted to give a final update of this Onan problem. Like usual, you guys were right on! The bridge rectifier was the culprit. Simple fix and works as it should!
Thank you!!!
Ken Shaffer
Marion Iowa
73 Canyon Lands, 455, Micro-level, Alum radiator, Alcoa wheels, Lenzi hubs/bearings, Howell EFI/EBL, Rostra Cruise, Custom interior
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| Re: Onan trouble shooting [message #343832 is a reply to message #343727] |
Sat, 01 June 2019 07:26 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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A point for others. Onan used a bridge with a relatively low reverse voltage rating. When you buy them by the thousands there's a savings. When you're replacing them one at a time, buy the 1KV version. It might be a dime more, and will survive much longer.
--johnny
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: Onan trouble shooting [message #343836 is a reply to message #343727] |
Sat, 01 June 2019 09:38 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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The lesson here is to test the bridge early if not first in the diagnostics and before flashing the field. Also meter the field Ohms before attempting to flash. Just a more logical approach and saves waisted steps.
John Lebetski
Woodstock, IL
77 Eleganza II
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