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


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  #41  
Old 08-08-2017, 12:55:37 AM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

I think the wiring diagram shows optional wiring connections for an electric fuel pump but it is not necessarily present there. I have never seen those wires in the control box but they could be. I will wait for the pics to see what they show and don't show, I think there may yet be some unaccounted for standard wiring connections. Cheers Dan
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  #42  
Old 08-08-2017, 07:41:20 AM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

So it appears that serial number begins 16C so the prize goes to KevinK. The build date appears to be Jan 1966 . Magneciter. The drawings Kevin posted should be correct.
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  #43  
Old 08-08-2017, 08:49:20 AM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

is that the solenoid that has an adjustable rod coming out of the bottom of it that is against the throttle shut off of the inject pump nothingbutdarts? if it is that already has a grounded wire and one that comes from the oil pressure sensor I think, (if not from this sensor from somewhere else, but def has 2 wires already)?
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  #44  
Old 08-08-2017, 09:02:26 AM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

ok so these 3 pics are the 2 wires in box, the one without black coated goes to the end about 6 inches away from box which I think Bigblockchev said fuel pump I mightr be mistaken who said it so sorry for toe stepping,
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  #45  
Old 08-08-2017, 09:04:37 AM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

the other wier is the thinner one that goes under the box , dont know if its a ground in or ontop of the gen head but it feels like it goes to the head inside or out ?? I dont know
the other wire that does go into the head is numbered 35 as you said and it does ohm out to about 3-16 depending on how good I can get the wires touching meter.
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  #46  
Old 08-08-2017, 09:06:53 AM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

ok here are some good pics of under the head end cover.
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  #47  
Old 08-08-2017, 04:34:14 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Ok I have a minute to type a couple of detailed questions,

The #35 wire from gen head goes to terminal block in box without a mate? What should it mate to and where does its mate go?

The thicker wire from gen head that goes to cntrl box is about a 10 gauge roughly, what should that attach to, I remember someone said I think Bigblockchev did that it comes from the exciter. does the diagram show that it does come from the head but instead from the charging part of it and goes to the rectifier than from rectifier to the amp gauge? Another wrench in this is I only see 1 wire coming from genhead and It seems I have 2, this one I ohmed out and another thinner one about a 12- 14 gauge wire, closer to 14gauge. I think I will look a lot better under the box and see if it grounds out or where it goes excactly. Any thoughts ?? I am stumped when it comes to wiring. I feel like pulling my hair out, I realy dont have much to do that though...LOL

Any help is appreciated guys. Thanks fall all.

Steve

---------- Post added at 01:34:14 PM ---------- Previous post was at 01:31:53 PM ----------

Looking at the pics, wires inside head are numbered and looks like E1,E2,C1,C2 and 35 are the main big ones
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  #48  
Old 08-08-2017, 09:41:33 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Looking at the diagram 35 goes to #9 on terminal block and from there to the S connection on the Start Solenoid K11 on the wiring diagram.
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  #49  
Old 08-08-2017, 11:08:20 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Here are some pics of a relatively clean control box for a magneciter machine. I can't identify which wire of the extra jacketed wires you are holding up since your hand is in the way. There are actually 2 wires which have an extra black jacket here is what one of them connects to. The first pic shows the wire with the extra jacket going to the end terminal #4 of the terminal block. the second pic shows it connecting to the hi temp sensor on the side of the head. The other side of the hi temp sensor goes to a ring terminal in pic 3. In pic 4 we see that wire with the ring terminal is connected to the connector on the side of the fuel solenoid.
The other jacketed wire connects to terminal #6 on the block and the other end goes to the oil pressure switch.
The fuel solenoid should not be connected to the oil pressure switch, please check to see if you have described that correctly. Cheers Dan
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  #50  
Old 08-09-2017, 12:02:07 AM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Nice slippers Dan! And Thanks for all the help!!
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  #51  
Old 08-09-2017, 09:01:49 AM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Dan thank you for your time and pics,
I did make the mistake with the oil pressure wiring, that is the one I thought I was told by previous owner who tore some stuff apart. anyway, I will correct this thanks to you.
I will need to find the hi temp sensor on the side of the head. didnt see anyrthing but I wasnt looking just for one. also in pic 1 looking at terminal #11 right side there is the diode rectifier. that goes from charging system to terminal #7 then through cr11 diode rectifier and back to terminal #8 and out to the relay start ignition? I think?
Whats your take on this?
also are you in a position of parting with this control box? if so parts or the hole?
I dont have the diode rectifier and spoke with allied, they said its discontinued..
probably some other parts I cant think of or know i=of until she fires up. Oh hi temp sensor on side of head.
have a great day,


Steve

MBB, Thank you,
I think I am seeing how the wire diagram goes a little better now thanks to your help and Dan. I am hoping I can get some carbon coming out of her exhaust by this weekend.
if so then I am going to do the cleaning.
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  #52  
Old 08-09-2017, 10:52:53 AM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Quote:
Originally Posted by JohnnyC View Post
I remove the plastic insulator from each connector, crimp the connector with the wire in it, solder the wire and connector, then use a glue sealer heat shrink tube over the crimped / soldered area
JohnnyC
New Jersey
I started doing almost that in the early 70's. Too many failed crimp connections. (yes, wrong wire/crimper/connectors I'm sure). But found I could get a very nice looking absolutely reliable connector by soldering. If there's going to be a chance of any flexing, I do a second filled heat shrink about twice as long as the first insulator/heatshrink, to give a bit more stability to the connection. (left over behavior from Deans connectors on servos).
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  #53  
Old 08-09-2017, 12:32:34 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Steve, I have the complete charge rectifier with heat sink if you want it. Came off my MDJE project. Also have a nice clean used start / disconnect relay, both yours if you can use them. Lmk

I also solder/heat shrink my crimps, but I only solder the very front of the crimp not the whole thing. If you solder the whole barrel the connection becomes brittle. By only soldering the front half of the barrel the wire still has the ability to flex. I still count on the crimp for mechanical strength, the solder maintains electrical integrity. I also heat gun the connections after installation, it relieves the stress imparted when installing / bending the connection into place. When I do heavy lugs (battery cables etc) I drill a small hole in the front of the barrel and solder through it for the same reason.
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  #54  
Old 08-09-2017, 02:24:59 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

PnishrPW,

Many many thankyou's. Yes I can use those parts for my rebuild, Let me know by a pm or how ever, what you want for them.
The wires I have corrected so far have been a soldier on the ends closest to the screw slot. This makes such a nice secure fit. I then slip the shrink fit back over. I am looking for some nicer friendlier ones that slip or just buy the ones with out and shrink fit new on??? I will wait for your response for the parts PnishrPW

Thanks again.
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  #55  
Old 08-09-2017, 02:41:03 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Pm me a phone number and I'll call when I get a min. Cr1 is pulled, relay is still in use, being swapped out soon. Price? Cup o cheap azz 7-11 or AmPm coffee if you're feeling generous. I don't drink Starbucks or the like...

Uninsulated terminals seem to cost more, I just use std cheaper insulated ones and pull the plastic off. NOT the cheapest ones. Youngs products out of Gig Harbor are decent - sold at McClendons and elsewhere.
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  #56  
Old 08-09-2017, 08:09:47 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

We will try to go through this one thing at a time so that it is less confusing. Here is a pic of the hi temp sensor. It is the black thing in the middle. It should be located between the control box and the head. They are subject to breakage very easily and can not be replaced without unbolting the control box and pulling it aside. Caution with the screws as they only have about 1/8"of thread. If the original is broken save the mounting bracket/socket as a generic one can be fitted using the bracket. You can also bypass the temp switch temporarily to get the set up and running.
To get more progress it would be helpful if you could post more pics of the control box after blowing it out with an air hose and cleaning it up. It is difficult to see what is connecting to what from the pics that you have posted.
If your objective is just to see if the set runs and generates you can jump the fuel solenoid with 12V , jump the preheat solenoid for 60 seconds, and jump the starter. It will run as long as the fuel solenoid is powered up. You may have to bleed the air out of the fuel lines by using the manual lever on the fuel pump and watching for fuel to come out of the return line. Cheers Dan
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  #57  
Old 08-09-2017, 08:33:48 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Might want to disconnect/disable the v/r while sorting out the engine issues. Wouldn't want to smoke it...
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  #58  
Old 08-09-2017, 10:15:27 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Dan, thanks very much for the pic, it is making sense, where your sensor is, i have a freeze plug. So now i dont know if that makes more complication? As for blowing the mouse crap out, i darn near blew up my compressor gettimg it as clean as it is if you want to call it that. And yes my intention is to get it to fire smooth and be an off the grid provider, than i want to show her off and make her puuuurrrrrrdy��
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Old 08-09-2017, 10:57:56 PM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

The sensor would be screwed to the head not the block, there are no freezeplugs in the heads. If it were there it would be about 2 inches above that freezeplug I suspect that the sensor is missing from your unit , probably due to failure. It does not make it any more complicated the wiring would just go from terminal #4 to the ring terminal on the fuel solenoid. Cheers Dan
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Old 08-10-2017, 08:43:02 AM
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Default Re: Onan 12 MDJC - 3r/2268d (1985)

Dan,

Thanks for that pic you sent, it shows me where I have the screws left in the head but no sensor, so I will bi pass it and run it straight to the ring terminal on the fuel solenoid.

PnishrPW,

whats the V/R
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