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Onan 12 MDJC - 3r/2268d (1985)


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  #1  
Old 08-01-2017, 08:47:57 AM
sscummins sscummins is offline
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Default Onan 12 MDJC - 3r/2268d (1985)

Hi all, wanted to thank all of you here for what help you give to the new and unknown, Been reading alot (more than when I was in school) and its very helpful.
Now onto my questions, I have a 12 mdjc - 3r/2268d (1985) and it is/was a marine, I have changed the exhaust to non-marine and looks pretty good. I had the injector pump rebuilt by accurate diesel in Florida along with my injectors. All is good now. The wiring in the control box is a mess. There was a birds nest (vacant) and when I removed it all the crap ad what ever they do in the nest caused alot of corrosive mess to the wires and connectors. It seems someone else started to rewire it with new connectors but not too recent. My question is what wires connect with what wires in the terminal blocks, there are 2 blocks, top one has like 5 wires on 1 side of it (going in or coming out) and opposite side has just 1 wire in the #1 marked slot, oh the 5 wires are in the opposite side of whats marked B+, 1, 2, 3, H. Is this correct? the bottom terminal bl;ock has 8 spots for wires,6 are filled some only on 1 side of the block? is this correct? Can someone shed some light on it, I have I think the wiring scu but I have a hard time reading wiring diagrams, my weakness.
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Old 08-01-2017, 09:03:35 AM
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Default Re: 12 mdjc - 3r/2268d (1985)

The B+,1,2,3,H are the remote start and heater wires. The bottom wires are the control wires for the system. Some may not be used. Post the full model and serial number. So we can get you the correct print.
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Old 08-01-2017, 09:23:43 AM
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Default Re: 12 mdjc - 3r/2268d (1985)

I don't know if this will help but look at post #14 here:

https://www.smokstak.com/forum/showthread.php?t=76793
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Old 08-01-2017, 05:19:30 PM
sscummins sscummins is offline
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Default Re: Onan 12 mdjc - 3r/2268d (1985)

Sorry for the lack of info, serial # is 16C859299
12MDJC-3R/2268D
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Old 08-02-2017, 03:48:20 PM
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Default Re: Onan 12 mdjc - 3r/2268d (1985)

Any chance you can post pictures of your box????
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Old 08-02-2017, 05:09:17 PM
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Default Re: Onan 12 mdjc - 3r/2268d (1985)

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Old 08-02-2017, 05:10:55 PM
sscummins sscummins is offline
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Default Re: Onan 12 mdjc - 3r/2268d (1985)

Its a bee's nest, well to be politically correct, it had a birds nest on top of most of the wires
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Old 08-02-2017, 07:16:16 PM
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Default Re: Onan 12 mdjc - 3r/2268d (1985)

Quote:
Originally Posted by sscummins View Post
Its a bee's nest, well to be politically correct, it had a birds nest on top of most of the wires
More than likely mice, not "the birds and the bees". Mouse urine is very corrosive and their teeth are hard on insulation.
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Old 08-03-2017, 07:43:03 AM
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Default Re: Onan 12 mdjc - 3r/2268d (1985)

I can't find your 12MDJC-3R/2268D generator in my database, so it is difficult to give you the correct wiring diagram.

I looked through the database for similar models, and came up with two that use the same wiring diagram: 12MDJC-3R2268S, and 15MDJCB-3R2268A. Perhaps this wiring diagram is correct for your model, or at least very close.
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Old 08-03-2017, 09:33:29 AM
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Default Re: Onan 12 mdjc - 3r/2268d (1985)

I couldn't find that model,but that print should be the one.
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Old 08-03-2017, 11:18:09 AM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Thank you very much, I dont know much about schematics or print reading, can anyone break down what the 5 or 6 wires and where they connect too? I dont want to wire something to something it shouldnt be wired to on the block? you all have been very kind by finding and sharing already, Many thanks again in advance.
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Old 08-03-2017, 11:23:46 AM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

I hate to kind of say bad news but, the way your control box looks all green and rusty from corrosion I might send a PM to BigBlock and ask him if he might have a MDJC control box that is in better shape that he might want to sell. Just saying. If nothing else yours needs to be pulled off and totally cleaned up.
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Old 08-03-2017, 01:05:35 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Yaeh I was thinking something like that but the funny thing is, when I bought it, I hooked a battery up to it and it cranked over great, and the injector pump needed to be rebiult and I through the injectors in with it and sent them to accurate diesel in florida, and Tim did a great job on them for a couplwe hundred bucks. I will PM him and see what he has to offer. Thank you.

---------- Post added at 10:05:35 AM ---------- Previous post was at 09:58:19 AM ----------

what is his name? I typed in BigBlock but it did not find that name?
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Old 08-03-2017, 01:17:07 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Bigblockchev is his user name, Dan is a good guy.
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Old 08-03-2017, 01:28:32 PM
sscummins sscummins is offline
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Thank you. I appreciate it
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Old 08-03-2017, 02:12:09 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Is this a critical use application? In a boat where NEEDED while out on the water? Just curious?
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Old 08-03-2017, 02:59:44 PM
sscummins sscummins is offline
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

The guy I bought it from through in an exhaust manifold (Non Marine) and the top water inlet connection for the heads and I changed it to be a back up for my home. He also included a spare head which later looking at them all, they are interchangeable from the looks of them.
But back to your question, it will be easily available to tinker with. from the sounds of alot of people here and in general these units are pretty durable and long lasting. Whats your opinion on them? Oh also I might be interested in selling the manifold for this marine application, I should put it on the for sale board right? what do you think someone would pay for it, it seems to be in very good and clean condition.
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Old 08-03-2017, 05:46:03 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

How you cooling it for home use?

There have been several threads in the recent past about fans, radiators, raw water and so on.
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Old 08-03-2017, 06:10:36 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

hi Grif,

When I bought it, he threw in a spare head, exhaust manifold (non marine) and the top head inlet/manifold for water, this was started to be fresh water cooled with still the marine setup, so I changed it over to fresh water and it had a radiator mounted on the front of it.
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Old 08-03-2017, 07:09:47 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Just out of curiosity, what are you using for a radiator?

Federal Way? I used to live in the Twin Lakes area, now down the hill in T-town.
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