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Onan Generators Restoring, operating and maintaining vintage Onan generators. When asking new questions about your generator, ALWAYS give your model number AND serial number.

Onan Generators

Decode model number... I've tried but failed.

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Old 01-24-2010, 05:17:48 PM
dryflyer dryflyer is offline
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Default Decode model number... I've tried but failed.

Looking for help in decoding this model number: 12RJC-31/1024R.
I've tried the posted resources but can't seem to find a definitive answer as the number format doesn't seem to exactly fit what is listed on the forum page relating to model number decoding. This generator is currently posted on ebay item #190367712942, and seems to fit what I've been looking for in a 120/240vac, propane, water cooled unit. I'd appreciate anyone who might confirm this and/or shed further light on the specifics before I consider purchase.

Thanks to all,
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Old 01-24-2010, 07:11:09 PM
Jim Rankin Jim Rankin is offline
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Default Re: Decode model number....I've tried but failed.

Well the problem is you left out the 3R between the the 12.5RJC- and the 31/1024R.

I see no reason to doubt the generator is as described in the ebay ad. The voltage code matches the 120/240 VAC output.

It was made in April of 1968 (from the serial number 0468................) so it's pretty old and it looks as if it has had a "Dupont overhaul" sprayed on it which can be good or bad depending on if the generator underneath is as good as the paint job. New paint sometimes causes buyers to pay more than they probably should for an old piece of machinery. I'm no expert, but the price may be a little on the top end for one that old.

One fly in the ointment is that this one is an older generator with the magneciter type voltage regulation and excitation system. The model number spec (the R at the end) would be a double letter beginning with AA if it had a more modern YD type generator end with a solid state regulator.

From what I've seen on the board here, the magneciters are probably more reliable than the YDs with some of the earlier/older boards, but if the wrong thing goes wrong with the regulator/exciter, the parts are very expensive to unavailable compared to the YD's circuit boards etc. There are aftermarket conversions available replace a bad magneciter for the same or less money than some of the parts for the magneciter. Other parts of the system aren't that expensive, like diodes etc.
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Old 01-24-2010, 08:17:48 PM
Isaac-1 Isaac-1 is offline
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Default Decode model number....I've tried but failed.

What Jim said.


p.s. This unit is advertised as set up for natural gas, propane is similar, but somewhat different, depending on your tank size, climate, etc. you will have to decide if you want to use liquid or vapor feed, and add the appropriate pressure regulators / vaporizer, depending on ebay deals, etc. this could add a few hundred dollars to your installation cost.

A couple of more things this unit seems to be on the east coast and you seem to be on the west coast, therefore freight on a fifteen hundred pound generator is likely to be a considerable percentage of the purchase cost.

Second your in California, make sure anything you buy is emission code legal, I don't know how it is with with propane generator, but as of last year California has for all practical purposes banned diesel generators that are more than 3-4 years old as gross polluters.
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Old 01-26-2010, 12:49:21 PM
dryflyer dryflyer is offline
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Default Re: Decode model number....I've tried but failed.

Thanks to all for the valuable info. Yes, I inadvertently left the R out before the 31....sorry about that. Your collective comments on the age and potential issues with the magniciter etc. were helpful. I have a 500 gallon propane tank with searate low pressure regulator at the power shed so don't expect any problems with fuel starvation. Yes, I'm in California and the lift gate freight charge was estimated at nearly $1000.00. I've been looking for a closer candidate since July without success. It seems most of the units of interest are clustered in the mid-west and east coast areas and even those were "pick-up only".

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Old 01-27-2010, 09:41:05 AM
Esteban32696 Esteban32696 is offline
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Default Re: Decode model number....I've tried but failed.

Try this site for bids on hauling. Be sure to let them know all the details of the shipment.
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