Onan Generator Not Running Properly

[charles w aulgur]

Todd,

I had the same symptoms as you described and went through the same
repairs you did, with the same results. As a last resort, I bought an
electronic ignition kit from Onam an modified it so it would work on our
"Power Drawer" unit. After installing the electronic ignition, all my
problems went away. My Onan has never started and ran as smoothly as it
does now. Now when I turn on something with applies a heavy load I
cannot detect any change in the Onan RPM. Apparently, the increased
spark plug voltage provided by the electronic ignition was enough to fix
whatever was causing the problem. I was so impressed with the
improvement I decided to describe how I made the modification and I
presented a seminar on the subject at the GMCWS rally at Albuquerque
last fall. You can review my presentation on the GMCWS web site
under Tech Center Number 27. It's well worth the money
($125) to make the change.

This is my first day on the GMC Motorhome Digest and the welcoming e-mail
said I should introduce myself: I am a retired mechanical engineer and
have owned a GMC for 15 years. Our current model is a 76 Royale which we
have had for 10 years. I spent my entire carrier working for General
Dynamics here in San Diego building and launching rocket ships. I am the
current Tech V. P. for GMC Western States Club.

Chuck Aulgur

 

[richard waters]

> After installing the electronic ignition, all my
> problems went away. My Onan has never started and ran as smoothly as it
> does now. Now when I turn on something with applies a heavy load I
> cannot detect any change in the Onan RPM. Apparently, the increased
> spark plug voltage provided by the electronic ignition was enough to fix
> whatever was causing the problem. I was so impressed with the
> improvement I decided to describe how I made the modification and I
> presented a seminar on the subject at the GMCWS rally at Albuquerque
> last fall.
>

Chuck,
Welcome to the group!

I've had my share of problems with my Onan. I think I've fixed most of them.

In your post you mentioned something that got my attention. You said that
"Now when I turn on something which applies a heavy load I cannot detect any
change in the Onan RPM." Well in my case now if I put a large load on the
generator, such as the running the microwave, heat coil in the air
conditioner and a quartz heater, the voltage (and resulting RPM) will
decrease from 120 volts to about 105 volts. I don't know if this is normal.
>From what you said, it sounds like the addition of electronic ignition may
minimize the drop?

What do you think?
Richard Waters
1976 PB, Troy, MI

 

[gene]

Welcome aboard Chuck

Now you can go up and see all your stuff I put on the web page
listed under projects.

gene

>Todd,
>
>I had the same symptoms as you described and went through the same
>repairs you did, with the same results. As a last resort, I bought an
>electronic ignition kit from Onam an modified it so it would work on our
>"Power Drawer" unit. After installing the electronic ignition, all my
>problems went away. My Onan has never started and ran as smoothly as it
>does now. Now when I turn on something with applies a heavy load I
>cannot detect any change in the Onan RPM. Apparently, the increased
>spark plug voltage provided by the electronic ignition was enough to fix
>whatever was causing the problem. I was so impressed with the
>improvement I decided to describe how I made the modification and I
>presented a seminar on the subject at the GMCWS rally at Albuquerque
>last fall. You can review my presentation on the GMCWS web site
> under Tech Center Number 27. It's well worth the money
>($125) to make the change.
>
>This is my first day on the GMC Motorhome Digest and the welcoming e-mail
>said I should introduce myself: I am a retired mechanical engineer and
>have owned a GMC for 15 years. Our current model is a 76 Royale which we
>have had for 10 years. I spent my entire carrier working for General
>Dynamics here in San Diego building and launching rocket ships. I am the
>current Tech V. P. for GMC Western States Club.
>
>Chuck Aulgur
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/

 

[david l greenberg]

On Fri, 24 Mar 2000 19:41:08 -0800 Charles W Aulgur
writes:
> This is my first day on the GMC Motorhome Digest and the welcoming
> e-mail
> said I should introduce myself: I am a retired mechanical engineer
> and have owned a GMC for 15 years. Our current model is a 76 Royale
> which we have had for 10 years. I spent my entire carrier working for
> General Dynamics here in San Diego building and launching rocket ships.
I am the current Tech V. P. for GMC Western States Club.
>
> Chuck Aulgur
Welcome, Chuck...we can always use your expertise and experience on the
Net!

David Lee Greenberg
GMC Motorhome Registry
Dedicated To The Preservation Of The GMC Classic!
www.gmcss.com/registry.htm

 

[tmaki1]

Chuck,

Welcome!

I've enjoyed reading your tech articles in back issues of
the GMCWS newsletters, and met Bud Bronson at the
San Diego swap meet a few weeks ago who told me to
look for the upcoming article on the carb pre-heat tube
replacement (he even gave me a sample part).

Glad to have another seasoned "tech-head" hanging out
here. Hope to meet you and other GMCWS members at
a rally sometime.

Toby Maki
'73 Glacier 230

> This is my first day on the GMC Motorhome Digest
>
> Chuck Aulgur

 

[richard waters]

> >From reading some post I would like to inject my opinion or method.
>
> Generator: The governor is to keep a set speed regulated. i.e.. US power =
> 60 Hz. Our power plants operate ate 3,600 RPM. Therefore we take 120 Hz/2
> poles (N & S) and produce a 3,600 RPM motor. 4 pole motor is 120/4=1,800 and
> so forth. Our instruments are dependant upon frequency; outside of
> acceptable parameters and they burn and crash. I use a fluorescant light
> which produces a 120 Hz frequency and monitor it via a photo tach. I then
> make my adjustments to regulate the RPM to produce 60 Hz power to the
> outlets. Whatever amperage you get is the condition of your generator. Don't
> adjust RPM to get voltage - you will fry stuff; and, we like stuff.
>

Samuel,
I guess I'm dense. You say " Don't adjust RPM to get voltage." Well how do you
adjust the voltage if you don't adjust the RPM? Isn't RPM the only variable
available to us for adjusting voltage? I don't understand.

Also I don't have a photo tach so I can't use a fluorescent light to check for
120 Hz frequency. Again don't you adjust RPM to get a specific frequency? Any
suggestions on what I should do?
Thanks,
Richard Waters
1976 Palm Beach
Troy, MI

 

[samuel pickens]

Hi all,

>From reading some post I would like to inject my opinion or method.

Generator: The governor is to keep a set speed regulated. i.e.. US power =
60 Hz. Our power plants operate ate 3,600 RPM. Therefore we take 120 Hz/2
poles (N & S) and produce a 3,600 RPM motor. 4 pole motor is 120/4=1,800 and
so forth. Our instruments are dependant upon frequency; outside of
acceptable parameters and they burn and crash. I use a fluorescant light
which produces a 120 Hz frequency and monitor it via a photo tach. I then
make my adjustments to regulate the RPM to produce 60 Hz power to the
outlets. Whatever amperage you get is the condition of your generator. Don't
adjust RPM to get voltage - you will fry stuff; and, we like stuff.

OK, everyone likes electronic gadgets. Battery compartment --- I chose
simplicity. Today we want different stuff than was available in 1973. Most
have electronic stuff that requires clean power (12 v). I like a good
stereo/CD system. Face it; there are some good stuff out there and the price
of music has gone up.
A good player is 1000$+ and up from there. Since we have one alternator and
two batteries we want auto monitoring/switching, ergo the blue box to keep
from over charging one of the batteries. But can produce leprosy current to
your dash and blow modern stuff. I have a tendency to charge a battery and
manually switch as desired. This gives me the advantages of two batteries
without the worry of anything going wrong and messing up a toy, a very
expensive toy. Again, since I don't like to worry; manual switching for the
power the battery to the coach when it's not hooked up to AC mains.

By taking this approach, I've never had a problem. There isn't forgiveness
in modern sensitive electronics. And, this approach is dependable and
secure. Yes, I like multiple batteries but only source one at a time. If you
have a piece of instrumentation it will at some point go bad - when it
messes up an expensive toy then it's not a question of replacing a cheap
battery switching mechanism.

I'm a consulting engineer and spend most of my life in this thing. I'm in it
now. Returned from FL, GA, NC, and TN from a three month trip. I've been
here a month and will leave this week for GA to consult and teach. This is a
way of life for me since my son left the nest; I travel a lot. I must have
dependability and these little things give it. The killer stereo is
protected by having clean power. You may want to equip yours with electronic
switching and filters. But, do the engineering and ensure dependability.
Myself, I have too much Scotchman in me and want to save money and will flip
the switch myself. Or is that scotch in me man?

Just for your consideration.

 

[edgar kremer]

> If you take all loads off the Onan and adjust the governor speed so that a
> voltmeter will read about 140 volts you'll find that it will keep near 120
> volts with a load on it. The maintenance manual shows to adjust the nut at
> the end of the wire that leads from the governor control arm. You can also
> adjust by checking the rpm if you have a tach you can hook up to the Onan.
> The GMC maintenance manual also shows that.

- --------------------------------------------

Emery, am I missing something here? Would I really want 140 volts no load??? If
I turned on a low amp piece of equipment (CD player?), I'd be making a trip to
the nearest junk yard.


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[edgar kremer]

> Also I don't have a photo tach so I can't use a fluorescent light to check for
> 120 Hz frequency. Again don't you adjust RPM to get a specific frequency? Any
> suggestions on what I should do?

- ----------------------------------------------------

To adjust freq, connect one lead from a neon test light to one side of the Onan's
output. Connect the other lead to one side of the power company's outlet.

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[david l greenberg]

On Tue, 28 Mar 2000 16:13:22 -0500 Edgar Kremer
writes:

>
> > Also I don't have a photo tach so I can't use a fluorescent light
> to check for 120 Hz frequency.

You should be adjusting speed to get about 61-62 Hz.

David Lee Greenberg
GMC Motorhome Registry
Dedicated to the preservation of the Classic GMC
http://www.gmcss.com/registry.htm

 

[edgar kremer]

>
> Onan's
> output. Connect the other lead to one side of the power company's outlet. >>
>
> This sounds like a nice simple way to set the Onan to 60 hertz. I'll try it
> and then increase the rpm slightly so as to raise the frequency to about 63
> no load. Please advise if we can assume that when the frequency is the same
> that the test light goes out (equal voltages?).

> Have you found any variance due to a voltage drop using an extension cord on
> the power company's line or
> isn't that enough to be a factor?
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM

- ---------------------------------------------------

Emery, extension cords do not factor in. The test light is out when the freq is
equal (see separate post for complete details).
Thanks for your interest.
- --

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