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Old 06-16-2010, 08:38 AM   #1
Join Date: Jun 2010
Posts: 2,601
Onan 12VDc Propane Genset

My 73 Excella 500 has a propane fired 12VDC genset. I called Onan and quoted the model and serial number and some parts are still available. I have pulled the unit and dropped it off at a small engine shop fora tear down and rebuild. They tell me that the Tecumseth engine parts are still available either from factory or aftermarket. I intend to rebuild the cabinet for it because it is extremely rusted out. I will keep everyone posted as the rebuild process goes through it's stages. The picture her is of someone elses unit I will take pics later as the repairs take place.
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Old 06-16-2010, 11:42 AM   #2
Wise Elder
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2010 30' Classic
Vintage Kin Owner
South of the river , Minnesota
Join Date: Dec 2009
Posts: 4,169
Interesting. A 12 vdc genset, as in, it doesn't produce 120 volts, just 12 volts DC? I've been looking for something like that but never found it at a price I'm willing to pay.
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Old 06-17-2010, 12:20 AM   #3
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contact wannabefulltimin. He has the same genset and is wikking to sell it.
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Old 08-09-2010, 03:01 PM   #4
Rivet Master
1973 31' Sovereign
Portland , Oregon
Join Date: May 2004
Posts: 1,255
Images: 22
I have one too...

As it happens I have one of these generators in my 1973 31' International. I have been slowly remodeling my Airstream and a few years back (maybe 4 years) I took the generator to an Onan service center that we have here in Portland, Oregon. The technicians that worked on it for me said that they had never personally seen one of these. They did not do a great deal too it cosmetically but the main problem it had was that the very old oil that was in it was basically a bunch of sludge. They had to fill the system with solvent a few times to get it to thin out enough to clean it out. They were able to get it running and tested its output at about 14.5 volts.

Since then it has been sitting around waiting for me to do something with it. This weekend one of our daughters and her family were visiting. My son-in-law and I hooked up propane to it from my BBQ tank and temporarily wired up the control panel and my Airstream battery to see what would happen. By the way the unit was out of the Airstream for this test. I was able to crank over the engine with the electric start feature and as soon as the air was out of the propane line it started right up! Not bad for a 1973 generator! What surprised me though was that when I hooked up my volt meter to the battery posts I found out that the unit was putting out about 18.25 volts. I frankly do not understand how that is possible from a unit that is rated to have an output in the range of 12 to 15 volts. I am also a bit concerned about applying that much voltage to my 12volt main line.

As far as the overall condition of the unit I do have surface rust on the various steel parts and it was a bit gunky from what might have been oil spilled somewhere along the line. It does not seem to be leaking oil so that is all I can think of to account for why it was so oily. We spent some time with some brake cleaner to degrease it and while it does not look perfect it looks way better than it did. The door appears to be stainless steel and is still pretty good looking. We did replace some of the insulation that was missing. We bought that at an auto parts store.

I am attaching a photo here that will probably look about the same as the one posted earlier. I will be interested in reading more about the overhaul process and comparing notes with others that have these units. I will eventually have to decide whether or not to do more to my unit. For the time being it seems like it should be usable providing I can resolve the voltage level issue. So here are some questions that I would love to have forum members weigh in on:

1.) What to do about the higher voltage level?

2.) Does anyone have operating instructions for this unit? I can see that there seems to be a choke and throttle adjustment but I do not know what settings are recommended. This could have something to do with the voltage level too although we tried adjusting it and could only get down to about 16 volts.

3.) My installation has a small control panel with a timer that can be set for up to 3 hours of run time. The question in my mind is how do I prevent battery overcharge if I were to set the timer for too long of a time. Is there anything about the generator or circuitry that would limit the charging level?

I think I will start another thread to ask about DC voltage ranges and voltage regulation...


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Only he who attempts the ridiculous can achieve the impossble.
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Old 08-09-2010, 03:27 PM   #5
Rivet Master
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Inland RV Center, In's Avatar
Corona , California
Join Date: Feb 2002
Posts: 16,497
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Onan Gen set

That gen set, was a great idea.

Was fairly quiet, ran on propane and had a 12 volt DC output, and didn't use much fuel.

Now for the good part.

It was, when it "worked" great.

However, if you traveled very much, it became useless.

It would not start, when you changed altitude by as little as 1000 (one thousand) feet. You had to once again, adjust the carb, or it would not start.

I felt it had great promise, but was very disappointing when it came to it's overall use.

If you don't change altitude, it's ok, but if you do, be prepared to adjust the carb.

For a traveling person, that became a huge negative, very quickly.

Andy Rogozinski
Inland RV Center
Corona, CA
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Old 08-09-2010, 04:04 PM   #6
Wise Elder
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2010 30' Classic
Vintage Kin Owner
South of the river , Minnesota
Join Date: Dec 2009
Posts: 4,169
In the 1970s timers were a common way to manage battery charging. They still work.

It is possible that there is no voltage regulation on your generator. That's not necessarily bad, as long as it's used appropriately. The batteries will put up with a limited amount of overcharging without damage as long as they're kept watered.

A circuit that shuts off the generator at a particular voltage could be built today without much fuss.

If you run it on mostly discharged batteries you'll probably see a much lower output voltage.
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