OK, next Onan question

Jim,

I wish I had looked at your response first, but I found the problem. It was wire #4 above. It was broken and we installed an new spade connector on
it. It ran perfectly with start and stop from both switches. We installed the cover for the control board and cable tied a few wires. After that
the generator went into fits like we had a couple of days ago with the points problem. I had several things going on at my hangar today and was
helping my daughter so this project got postponed tomorrow.

I can not win at this point. But we will try again tomorrow.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
I did that for a guy about 10 or 12 years ago that bought a coach with the wires cut off to the alternator. It is still working fine. That was in
the back of my mind if the alternator coils were open. It turns out that they were not bad. All we had was a wiring problem.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
I am still working on this generator from hell. I thought and still think that I still have all of the wiring corrected. Now I am fighting a blown 5
amp fuse after starting. It does it almost every time. I finally installed a temporary circuit breaker to keep from going through fuses. I think I
have traced it down to the fuel pump. A Fluke amp probe show a stead 3.1 amps going to the board with an occasional very brief jump to slightly over
5 amps. I will try a replacement aviation Facet or Bendix fuel pump tomorrow. If it were voltage spikes I could see it on an oscilloscope but I do
not have am amp probe for it.

The second bug is still the up to speed circuit. I had it working for a while and not it start and stops again. I finally checked the output of the
alternator and it is a steady 24 VAC. It should be 28 to 30 or 31. Tomorrow I'll probably remove the flywheel and inspect the coils and inside
flywheel for dirt and rust. I can see no way to bring up the voltage other than that. It reads 24 VAC (NOT 28) when plugged into the board or
disconnected from the board.

My final shot might be to jumper out the resistor in series wit K2. I do not remember the value of that item on a dinosaur board but I though George
Z's resistor read something like 22 or 44 ohms. On the genuine Onan board that resistor is 200 ohms.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Good morning all,
If I may,I would like to ask an Onan on this thread. I fired up the
Onan and started one of the A/C units all is good running fine. About 5
minutes later started the 2nd unit everything is purring right along as it
should.

I left and went to pick up grand kids from school and another errand, gone
about an hour total. Got home Onan running fine. I thought man it's going
to me nice and cool in here. Nope it was hot and no A/C unit was running.
Ah s***t I said. Turns out no 120V at all. Checked breaker box etc.
Nada. Looked at reset button the Onan, ok. Got out service manual, looked
at possible causes. Where do I start first with this now?

Big thanks in advance,

Jim Ernst
77 Palm Beach
Columbus, NE
Currently on location
In Colorado Springs area.

I am still working on this generator from hell. I thought and still think
that I still have all of the wiring corrected. Now I am fighting a blown 5
amp fuse after starting. It does it almost every time. I finally
installed a temporary circuit breaker to keep from going through fuses. I
think I
have traced it down to the fuel pump. A Fluke amp probe show a stead 3.1
amps going to the board with an occasional very brief jump to slightly over
5 amps. I will try a replacement aviation Facet or Bendix fuel pump
tomorrow. If it were voltage spikes I could see it on an oscilloscope but I
do
not have am amp probe for it.

The second bug is still the up to speed circuit. I had it working for a
while and not it start and stops again. I finally checked the output of the
alternator and it is a steady 24 VAC. It should be 28 to 30 or 31.
Tomorrow I'll probably remove the flywheel and inspect the coils and inside
flywheel for dirt and rust. I can see no way to bring up the voltage other
than that. It reads 24 VAC (NOT 28) when plugged into the board or
disconnected from the board.

My final shot might be to jumper out the resistor in series wit K2. I do
not remember the value of that item on a dinosaur board but I though George
Z's resistor read something like 22 or 44 ohms. On the genuine Onan board
that resistor is 200 ohms.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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There is a possibility that its a bad breaker on the top of the Onan or perhaps a bad bridge rectifier.

First make sure that the cord from the Onan is plugged into the receptacle..

Take the cover off the breaker box at the top of the Onan.
Use a voltmeter (VOM). Start the Onan and check the AC voltage from the left side of the breaker to ground.
If there is no voltage there its probably the bridge rectifier.
If there is 120 volts there then check the right side of the breaker. If there is voltage there then the problem is in the wires going to your inside breaker box or a bad connection in the box or a bad breaker in that box.
If there is no voltage there reset the Onan breaker. If still no voltage then that breaker is bad.

Let us know what you find and we’ll offer more suggestions.
connection
Emery Stora
77 Kingsley
Frederick, CO

>
> Good morning all,
> If I may,I would like to ask an Onan on this thread. I fired up the
> Onan and started one of the A/C units all is good running fine. About 5
> minutes later started the 2nd unit everything is purring right along as it
> should.
>
> I left and went to pick up grand kids from school and another errand, gone
> about an hour total. Got home Onan running fine. I thought man it's going
> to me nice and cool in here. Nope it was hot and no A/C unit was running.
> Ah s***t I said. Turns out no 120V at all. Checked breaker box etc.
> Nada. Looked at reset button the Onan, ok. Got out service manual, looked
> at possible causes. Where do I start first with this now?
>
> Big thanks in advance,
>
> Jim Ernst
> 77 Palm Beach
> Columbus, NE
> Currently on location
> In Colorado Springs area.
>

>
> I am still working on this generator from hell. I thought and still think
> that I still have all of the wiring corrected. Now I am fighting a blown 5
> amp fuse after starting. It does it almost every time. I finally
> installed a temporary circuit breaker to keep from going through fuses. I
> think I
> have traced it down to the fuel pump. A Fluke amp probe show a stead 3.1
> amps going to the board with an occasional very brief jump to slightly over
> 5 amps. I will try a replacement aviation Facet or Bendix fuel pump
> tomorrow. If it were voltage spikes I could see it on an oscilloscope but I
> do
> not have am amp probe for it.
>
> The second bug is still the up to speed circuit. I had it working for a
> while and not it start and stops again. I finally checked the output of the
> alternator and it is a steady 24 VAC. It should be 28 to 30 or 31.
> Tomorrow I'll probably remove the flywheel and inspect the coils and inside
> flywheel for dirt and rust. I can see no way to bring up the voltage other
> than that. It reads 24 VAC (NOT 28) when plugged into the board or
> disconnected from the board.
>
> My final shot might be to jumper out the resistor in series wit K2. I do
> not remember the value of that item on a dinosaur board but I though George
> Z's resistor read something like 22 or 44 ohms. On the genuine Onan board
> that resistor is 200 ohms.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Thanks do much Emery I'll working on it in a little bit here and I'll let
you know what I find.

Jim

> There is a possibility that its a bad breaker on the top of the Onan or
> perhaps a bad bridge rectifier.
>
> First make sure that the cord from the Onan is plugged into the
> receptacle..
>
> Take the cover off the breaker box at the top of the Onan.
> Use a voltmeter (VOM). Start the Onan and check the AC voltage from the
> left side of the breaker to ground.
> If there is no voltage there its probably the bridge rectifier.
> If there is 120 volts there then check the right side of the breaker. If
> there is voltage there then the problem is in the wires going to your
> inside breaker box or a bad connection in the box or a bad breaker in that
> box.
> If there is no voltage there reset the Onan breaker. If still no voltage
> then that breaker is bad.
>
> Let us know what you find and we’ll offer more suggestions.
> connection
> Emery Stora
> 77 Kingsley
> Frederick, CO
>

> >
> > Good morning all,
> > If I may,I would like to ask an Onan on this thread. I fired up the
> > Onan and started one of the A/C units all is good running fine. About 5
> > minutes later started the 2nd unit everything is purring right along as
> it
> > should.
> >
> > I left and went to pick up grand kids from school and another errand,
> gone
> > about an hour total. Got home Onan running fine. I thought man it's going
> > to me nice and cool in here. Nope it was hot and no A/C unit was running.
> > Ah s***t I said. Turns out no 120V at all. Checked breaker box etc.
> > Nada. Looked at reset button the Onan, ok. Got out service manual,
> looked
> > at possible causes. Where do I start first with this now?
> >
> > Big thanks in advance,
> >
> > Jim Ernst
> > 77 Palm Beach
> > Columbus, NE
> > Currently on location
> > In Colorado Springs area.
> >

> >
> > I am still working on this generator from hell. I thought and still
> think
> > that I still have all of the wiring corrected. Now I am fighting a
> blown 5
> > amp fuse after starting. It does it almost every time. I finally
> > installed a temporary circuit breaker to keep from going through fuses.
> I
> > think I
> > have traced it down to the fuel pump. A Fluke amp probe show a stead 3.1
> > amps going to the board with an occasional very brief jump to slightly
> over
> > 5 amps. I will try a replacement aviation Facet or Bendix fuel pump
> > tomorrow. If it were voltage spikes I could see it on an oscilloscope
> but I
> > do
> > not have am amp probe for it.
> >
> > The second bug is still the up to speed circuit. I had it working for a
> > while and not it start and stops again. I finally checked the output of
> the
> > alternator and it is a steady 24 VAC. It should be 28 to 30 or 31.
> > Tomorrow I'll probably remove the flywheel and inspect the coils and
> inside
> > flywheel for dirt and rust. I can see no way to bring up the voltage
> other
> > than that. It reads 24 VAC (NOT 28) when plugged into the board or
> > disconnected from the board.
> >
> > My final shot might be to jumper out the resistor in series wit K2. I do
> > not remember the value of that item on a dinosaur board but I though
> George
> > Z's resistor read something like 22 or 44 ohms. On the genuine Onan
> board
> > that resistor is 200 ohms.
> > --
> > Ken Burton - N9KB
> > 76 Palm Beach
> > Hebron, Indiana
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
> Start the Onan and check the AC voltage from the left side of the breaker to ground. If there is no voltage there its probably the bridge rectifier.

An Onan that has recently generated 120V will have enough permanent magnetic field remaining in the iron to generate a few volts even if the bridge or the other parts of the excitation circuit are bad. If a few volts are present then that is a good sign that the armature and brushes are OK and they can be ruled out as the source of the problem and further troubleshooting can concentrate on the bridge and the excitation circuit. Do the tests that Emery has described and let us know the results.

—Jim

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
 
There is a good chance as Emory and Jim said, that either the breaker or bridge rectifier are bad. One of the things I had to do on this "Onan from
Hell" was replace a bad bridge rectifier.

I also replaced a bad Circuit Breaker on a different Onan several years ago.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Thanks Jim and Ken. Checked both sides of breaker, no voltage. I tried
different grounding paths to make sure as well.

Ken I hope my Onan doesn't turn into the sequel Onan from Hell 2.

Thanks so much!
Jim Ernst
77 Palm Beach
Columbus, NE
Falcon, CO

> There is a good chance as Emory and Jim said, that either the breaker or
> bridge rectifier are bad. One of the things I had to do on this "Onan from
> Hell" was replace a bad bridge rectifier.
>
> I also replaced a bad Circuit Breaker on a different Onan several years
> ago.
>
>
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
> Thanks Jim and Ken. Checked both sides of breaker, no voltage. I tried
> different grounding paths to make sure as well.
>
> Ken I hope my Onan doesn't turn into the sequel Onan from Hell 2.
>
> Thanks so much!
> Jim Ernst
> 77 Palm Beach
> Columbus, NE
> Falcon, CO

Jim,

It sounds like you have diagnostic paths right, and with Jim and Ken for help you should get it.
I almost hate to bring this up, but I have run into three open fields so far.
So, when you are checking the bridge rectifier out, take just a moment to look for the ~36Ω that the field should be. If it is not, then you need to
get with Jim Miller about fixing that.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Hello Matt, thanks for the input.
At present I'm trying to figure out how to properly test the rectifier.
Also, oddly enough, while I had it running a bit ago I did some checking
and realized I have a non charging condition from the Genny's alternator
As well.

Jim

> > Thanks Jim and Ken. Checked both sides of breaker, no voltage. I tried
> > different grounding paths to make sure as well.
> >
> > Ken I hope my Onan doesn't turn into the sequel Onan from Hell 2.
> >
> > Thanks so much!
> > Jim Ernst
> > 77 Palm Beach
> > Columbus, NE
> > Falcon, CO
>
>
> Jim,
>
> It sounds like you have diagnostic paths right, and with Jim and Ken for
> help you should get it.
> I almost hate to bring this up, but I have run into three open fields so
> far.
> So, when you are checking the bridge rectifier out, take just a moment to
> look for the ~36Ω that the field should be. If it is not, then you need to
> get with Jim Miller about fixing that.
>
> Matt
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
> At present I'm trying to figure out how to properly test the rectifier.

The easiest way to test it is to buy a new one. And a spare. Unless your time is worth microcents per hour or you are a EE that understands the nuances of modern autoranging VOMs then you’d be money ahead to buy new product - then drop it in - and move along to the next troubleshooting step. Digikey, Mouser or any of our GMC dealers can put a known good one in your hands in no time flat.

—Jim

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
 
Well, it still isn't running. Replaced the fuel pump and still have the spiking over 5 amp condition blowing fuses and the failure of the alternator
30 VAC for up to speed that might be the cause of both problems. I am returning tomorrow to pull the flywheel and see what I have. We found an 12 DC
back circuit and now think that the alternator pick up coils might be the cause of both bugs.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Well, the GMC from hell is running. What was the problem and what fixed it? At this point I do not know. We did we did so much and changed so much
that I'm not sure. Yesterday I tore the alternator apart and cleaned a lot of garbage out of it, cleaned off a lot of oil, and fixed an oil leak.
We also found 2 additional wiring errors.

Thanks every one for all of the help.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Jim,
Thanks for the insight, it makes perfect sense. I'm going to be ordering
one soon...I've been working on a Rostra Cruise control install that has
most of the hair I did have left gone, hopefully that will be done soon.
The does not have juice come from the Alternator either. Are they both
related or two separate issues?

Thanks so much,

Jim Ernst
Columbus, NE
Falcon, CO

>
> > At present I'm trying to figure out how to properly test the rectifier.
>
> The easiest way to test it is to buy a new one. And a spare. Unless your
> time is worth microcents per hour or you are a EE that understands the
> nuances of modern autoranging VOMs then you’d be money ahead to buy new
> product - then drop it in - and move along to the next troubleshooting
> step. Digikey, Mouser or any of our GMC dealers can put a known good one in
> your hands in no time flat.
>
> —Jim
>
> Jim Miller
> 1977 Eleganza
> 1977 Royale
> Hamilton, OH
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
> "The does not have juice come from the Alternator either. Are they both related or two separate issues?"

I do not understand this. The “” does not have juice?

—Jim


Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
 
Sorry about that Jim, I did not proof read my question.
There is no charge to batteries or 120V, both quit at same time. My
question is then, are these 2 separate issues to fix or related in some
way?

Thanks,

Jim E

>

>
> > "The does not have juice come from the Alternator either. Are they both
> related or two separate issues?"
>
> I do not understand this. The “” does not have juice?
>
> —Jim
>
>
> Jim Miller
> 1977 Eleganza
> 1977 Royale
> Hamilton, OH
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
> Sorry about that Jim, I did not proof read my question.
> There is no charge to batteries or 120V, both quit at same time. My question is then, are these 2 separate issues to fix or related in some way?
>
> Thanks,
>
> Jim E

Jim,

Again some clarification is needed.

All the PowerDrawer Onans did have a voltage regulator to charge just the Onan's own starting battery (like mine), but most have been removed as they
start from the house battery. The house bank is maintained by the converter/charger and that device is powered by the Onan's 120VAC output.

Does yours even still have the Presolite regulator?

Matt

--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Matt,
Thanks for the info, I believe it does but not sure really. This is the
first time I have had to mess with genset so not all that familiar. Now the
Suburban heater won't light, blower starts up but that's all. I have gas
the stove lights and the refer is cold.

thanks again,

Jim Ernst
77PB
77 Kingsley
Columbus, NE
Falcon, CO
 
> Matt,
> Thanks for the info, I believe it does but not sure really. This is the
> first time I have had to mess with genset so not all that familiar. Now the
> Suburban heater won't light, blower starts up but that's all. I have gas
> the stove lights and the refer is cold.
>
> thanks again,
>
> Jim Ernst
> 77PB
> 77 Kingsley
> Columbus, NE
> Falcon, CO

Jim,

That is often the sail switch or an obstruction in airpath that keep the air from getting to a speed that the control knows it is working.

I bet that will be fun. The manuals are all at Bdub's.

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