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Onan Generators

Onan GenSet - project rebuild


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  #1  
Old 06-19-2017, 08:20:40 AM
gmdoctor gmdoctor is offline
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Default Onan GenSet - project rebuild

I've been looking for a generator for a good backup for my house/shop for years. The newer models (cheap ones), never seem to last. I'm here in the panhandle of Florida and it seems we have more power outages than i have ever experience. Last week i came across an older Onan and it was nearly fully intact. Mice have made a home in it for quite some time, and have enjoyed the wiring and insulation. Long story short, i got the engine running on propane, but i have nothing to test the genset portion. i will post pics as i can. Model No. 15.0JC-18R/15026AB and Serial # K830684756
As far as i can tell it has a build date of 1983. The carb looks like it was submerged in the gulf for years (appearance only) so gas will not move through it. If anyone can help me locate a good schematic for this i'd be eternally grateful. The engine side i can just about figure out, but reference material is always great to have around. As for the Gen side, i am totally dependent upon the masters in here. but i just need to get this thing cleaned up and running again. Anyone have a good source for parts for these older sets? I'd love to find a reliable source. Thanks in advance!!
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Old 06-19-2017, 08:42:35 AM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Onan GenSet - project rebuild

Look at the amp meter. If it is charging it is producing power. How much you will need a volt meter to find out. Give us time we can get you all the manuals and information you need. I would leave it on LP/NG. The gasoline side can be a pain sometimes.

Onan Parts is a seller of parts on this site.
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Old 06-19-2017, 09:10:42 AM
gmdoctor gmdoctor is offline
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Default Re: Onan GenSet - project rebuild

Thanks for the quick response Billy. I am a firm believer in OE parts. And i didn't look at the amp meter when i got this thing to run before i started to pull it down. I noticed it having a bunch of parts missing and thought it best to see what i may need to fix this before i put it into use. It has a bunch of wire emanating from the generator. they are separated and tied into 4 groups. i am leaving this for a later time to get straight.
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Old 06-19-2017, 09:12:34 AM
Ray Lynch Ray Lynch is offline
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Default Re: Onan GenSet - project rebuild

gmdoctor
Welcome to the site.
Manuals are available at the attached link. Do not run the set more than a few minutes without having the side tins installed. Otherwise it could overheat.
Good luck with your set.
Ray

http://www.twinslan.net/~n0nas/manuals/onan/
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Old 06-19-2017, 09:19:07 AM
Kevin K Kevin K is offline
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Default Re: Onan GenSet - project rebuild

Your model 15.0JC-18R/15026AB doesn't show up in my database, but a 12.5JC-18R/15026AB does. They are most likely the same machine, but yours has a 15Kw generator end. The good news is your has an extended stack, which gives you the full 15Kw on single phase.

I have attached the build sheet for the 12.5JC-18R/15026AB. I would guess the wiring diagram should be the same for your machine.
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File Type: pdf 125jc18r15026ab.pdf (25.0 KB, 30 views)
File Type: pdf 612-5559.pdf (145.1 KB, 34 views)
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Old 06-19-2017, 09:21:28 AM
gmdoctor gmdoctor is offline
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Default Re: Onan GenSet - project rebuild

Thanks Ray, good advice. I never let it run more than a min. I just wanted to see if it would run at all. Thanks for the link!
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Old 06-19-2017, 09:23:46 AM
nothingbutdarts nothingbutdarts is offline
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Default Re: Onan GenSet - project rebuild

Did you pull the voltage regulator cover off and then pull the voltage regulator off the control box to look for mice damage? I know you said you found some but didn't say where. They also like it inside the generator end, you might pull the end bell cover off along with the little rectangular mesh cover off the charge resistor and blow it out real good with air if you already haven't.

I just recently bought a 15.0JC but, mine was three phase and not extended stack like yours and in single phase it's only good for 12.5KW.
The control box and V/R were all good but, the gen. end had a lot of stuff in it!

Last edited by nothingbutdarts; 06-19-2017 at 09:36:30 AM.
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Old 06-19-2017, 09:30:53 AM
gmdoctor gmdoctor is offline
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Default Re: Onan GenSet - project rebuild

Kevin, that's awesome thank you. Once again though, the genset being stacked i wouldn't know the difference. I have never had any schooling on this. small portables are easy to fix. this set is foreign to me.

i pulled it down and found one wire completely chewed in half, and another one with no insulation let on it. the later was to the starter.
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Old 06-19-2017, 10:44:49 AM
gmdoctor gmdoctor is offline
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Default Re: Onan GenSet - project rebuild

As for pulling the bell end, i haven't gotten that far yet. Do they make replacement harnesses for these models? If not i can make my own. I have a bunch of pictures of everything, but i don't see where i can post more.
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Old 06-19-2017, 10:51:44 AM
len k len k is online now
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Default Re: Onan GenSet - project rebuild

Sounds extended stack (good), nameplate says at 120/240 can make all 15 kw on single phase (62.5 amp rating). Likely a 12 wire genhead ( 6 winding) so have to wire it right to get that 15kw on single phase.

I see a propane tank fitting stuck in the vapor fuel line to carb. It can work if you do a lot of continuous tweaking of the tank valve to get flow to follow electrical load during testing .

But for actual use your going to need a pressure regulator to reduce propane tank pressure down to ~ 11 inch W.C. pressure. Then pipe that to a demand regulator, which will flow fuel proportional to engine's needs.

Tri-fuel carb on my similar 7.5 kw JB had all the idle adjustment screws froze from rust. Took it apart and CAREFULLY heated aluminum casting at the screws and was able to work them out and wire wheel rust off them. Aluminum expands 3X faster then steel screws. I put them back in with anti-seize. Need to not overheat the aluminum, it melts without notice, doesn't glow red. Think even a propane/air turbo torch can get you to melting temp, so have to be carefull.

Last edited by len k; 06-19-2017 at 11:15:06 AM.
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