Generators and Motors
[Home] - [HELP] - [Forums] - [Library] - [Photo Gallery] - [Groups] - [Classified Ads] - [Subscribe] - [Links] - [Books] - [Sponsors] -

Go Back   SmokStak > SmokStak® Vintage Electrical Equipment > Generators & Motors General Discussion > Onan Generators
Forgot Password? Join Us!

Notices

Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

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


this thread has 76 replies and has been viewed 1876 times

Reply
 
Thread Tools Display Modes
  #21  
Old 08-03-2017, 07:57:21 PM
MBB MBB is offline
Registered-III
 
Join Date: Apr 2009
Location: Elk Grove Village IL USA
Posts: 3,038
Thanks: 1,293
Thanked 2,283 Times in 1,256 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Here is another possibility. Could it be 12.0MDJC3CR2268AD or 12.0MDJC18R2268AD both use the same wiring diagram. OP can you tell how many wires come out of the generator end the "t wires" Is it 3, 4, or 12 ? They would be the ones feeding an outlet or supplying the power. Were trying to find the correct diagram. I believe though it is either the one KevinK posted or the one I posted. I thought I had read it was a 12 lead. I went back and read the thread again and it and didnt say anything about that, must have been another thread.
Attached Files
File Type: pdf 612-6065.pdf (259.4 KB, 22 views)

Last edited by MBB; 08-04-2017 at 06:41:26 AM.
Reply With Quote
The Following User Says Thank You to MBB For This Post:
Sponsored Links
  #22  
Old 08-03-2017, 08:52:38 PM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 3,841
Thanks: 1,081
Thanked 1,746 Times in 1,034 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

sscummins, I received and replied to your PMs. Not sure if you read them yet. As for your control box, it will need a complete overhaul. It is not hard to do, but will take time and planning.

I had to redo my 15.0 JC's control box. Although it was not as bad as your box, none the less it had to be totally rewired. Since your genset is a diesel it has more wires when comparing my control box with yours.

As mentioned, make sure you have the proper schematic and wiring diagram(s) for your genset. Secondly, take LOTS of pictures during the entire rebuild. Take pictures from different view points too. Many times I see thing in my pictures that I missed by eye when at the control box. More picture the better. Make sure your picture are clear, not the typical Craiglists pictures that are blurry and worthless.

Just to show you my control box from start to finish, I attached 4 pictures below. The first 2 pictures show the damages in the control box and after removing most of the wires and components. The last 2 pictures show the end of reconstruction. I have several hundred pictures showing everything in between. By the way, my JC also started and ran with mouse piss and chewed wires. Onans are very resilient to lots of damage because they are built tough. Mouse piss could not destroy my JC and human piss could not stop my 4.0 BFA.


JohnnyC
New Jersey
Attached Thumbnails
Click image for larger version

Name:	001.jpg
Views:	43
Size:	175.1 KB
ID:	287842   Click image for larger version

Name:	002.jpg
Views:	43
Size:	123.1 KB
ID:	287843   Click image for larger version

Name:	003.jpg
Views:	49
Size:	136.0 KB
ID:	287844   Click image for larger version

Name:	004.jpg
Views:	48
Size:	143.3 KB
ID:	287845  

Reply With Quote
The Following User Says Thank You to JohnnyC For This Post:
  #23  
Old 08-04-2017, 09:44:54 AM
sscummins sscummins is offline
Registered
 
Join Date: Jul 2017
Location: Federal Way, Washington
Posts: 37
Thanks: 27
Thanked 4 Times in 2 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Kevin K posted a wiring diagram, is that the correct one? or is MBB the correct posted one above?
Also, thats JohnnyC for great advise as with everyone one else. I cant thank all of you enough and I dont want to miss thanking anyone at all, so if I did forget, it was unintentional. JohnnyC where can I purchase all my components connectors for in the box?
Oh the wiring diadram I have is from an early=ier post to this thread. I tried going back when posting this one before but it erased all I typed and oh how I hate typing. I rather have grease on my finger tips then black keyboard. LOL
Thanks

Thanks not Thats JohnnyC
Reply With Quote
  #24  
Old 08-04-2017, 12:15:49 PM
grif grif is offline
Registered-III
 
Join Date: Oct 2011
Location: Yakima, Washington
Posts: 1,228
Thanks: 412
Thanked 317 Times in 234 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Quote:
Originally Posted by JohnnyC View Post
Secondly, take LOTS of pictures during the entire rebuild. Take pictures from different view points too. Many times I see thing in my pictures that I missed by eye when at the control box. More picture the better. Make sure your picture are clear, not the typical Craiglists pictures that are blurry and worthless.

JohnnyC
New Jersey
What on earth did we do before digital cameras? I use my phone non-stop for note taking during projects.

JonnieC: Do you slip the insulator off the ring connectors, solder then slide the insulators back on or actually depend on the crimp?
Reply With Quote
  #25  
Old 08-04-2017, 12:30:53 PM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 3,841
Thanks: 1,081
Thanked 1,746 Times in 1,034 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Quote:
Originally Posted by grif View Post
What on earth did we do before digital cameras? I use my phone non-stop for note taking during projects.

JonnieC: Do you slip the insulator off the ring connectors, solder then slide the insulators back on or actually depend on the crimp?
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 of the connector. Overkill, but that is how I do things - The American way with pride, not the cheap-azz Chinese way.

JohnnyC
New Jersey
Reply With Quote
The Following 2 Users Say Thank You to JohnnyC For This Post:
  #26  
Old 08-04-2017, 03:17:47 PM
sscummins sscummins is offline
Registered
 
Join Date: Jul 2017
Location: Federal Way, Washington
Posts: 37
Thanks: 27
Thanked 4 Times in 2 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Can anyone know where to get the internal components for the control Box?

JohnnyC,

where can I find the parts to rebuild my control box?
Reply With Quote
  #27  
Old 08-04-2017, 05:07:55 PM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 3,841
Thanks: 1,081
Thanked 1,746 Times in 1,034 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Quote:
Originally Posted by sscummins View Post
Can anyone know where to get the internal components for the control Box?

JohnnyC,

where can I find the parts to rebuild my control box?
Onanparts.com, Ebay, Craigslist, Asking on this forum. There is a thread on this site titled "Onan Parting Out Thread" see link below.

https://www.smokstak.com/forum/showthread.php?t=99191

Lots of the work requires elbow grease as some parts may clean up.

Maybe if you are lucky, someone may be parting out an Onan 12 MDJC with a compatible control box in good condition and you can negotiate a deal. That will save you lots of time. For me, I simply rebuild them which is my therapy otherwise I go crazy bored . I rebuilt from ground up a control box for a 15.0 JC, 6.5 NH, 4.0 BFA and some work on a 15 RJC. If I can do it, so can you as some of my friends tell me I am retarded (or worse). Plan, take zillions of pictures, ask questions here and you will succeed.

JohnnyC
New Jersey
Reply With Quote
The Following User Says Thank You to JohnnyC For This Post:
  #28  
Old 08-04-2017, 05:10:29 PM
sscummins sscummins is offline
Registered
 
Join Date: Jul 2017
Location: Federal Way, Washington
Posts: 37
Thanks: 27
Thanked 4 Times in 2 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Thank you again.
Reply With Quote
  #29  
Old 08-05-2017, 07:39:14 AM
Kevin K Kevin K is offline
Registered-III
 
Join Date: Jan 2005
Location: upstate New York USA
Posts: 3,478
Thanks: 3,110
Thanked 3,439 Times in 1,874 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Quote:
Originally Posted by sscummins View Post
Kevin K posted a wiring diagram, is that the correct one? or is MBB the correct posted one above?
You need to verify the wiring diagram with your generator. The single spec letter in the model number indicates a Magneciter generator, so I limited my search to those models. Mike assumed it may be a later model using an electronic voltage regulator, and he may be correct. Check your generator to see if it has a YD generator end and electronic voltage regulator( newer model) or a Magneciter (older model).
Reply With Quote
  #30  
Old 08-05-2017, 08:33:01 AM
Max Thompson Max Thompson is offline
Sponsor
 
Join Date: May 2009
Location: N.W. Missouri, USA
Posts: 5,717
Thanks: 4,951
Thanked 5,252 Times in 2,873 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Quote:
Originally Posted by sscummins View Post
where can I find the parts to rebuild my control box?
I get mine from Allied electronics. Terminal strips and replacement relays & sockets. The link below has the part #s for the relays and sockets. Note the start disconnect / ignition relay has a 6-V coil. I use the 12-V relay to replace the start solenoid inside the box.

https://www.smokstak.com/forum/album.php?albumid=1428
Reply With Quote
  #31  
Old 08-05-2017, 03:15:56 PM
MBB MBB is offline
Registered-III
 
Join Date: Apr 2009
Location: Elk Grove Village IL USA
Posts: 3,038
Thanks: 1,293
Thanked 2,283 Times in 1,256 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Quote:
Originally Posted by Kevin K View Post
You need to verify the wiring diagram with your generator. The single spec letter in the model number indicates a Magneciter generator, so I limited my search to those models. Mike assumed it may be a later model using an electronic voltage regulator, and he may be correct. Check your generator to see if it has a YD generator end and electronic voltage regulator( newer model) or a Magneciter (older model).
Kevin I saw the age 1985 and figured it had to be a non Magneciter. An AD is viewed as a D. I also counted the items in the control box and they match the drawing I posted. Without getting answers its difficult to determine.
Reply With Quote
  #32  
Old 08-05-2017, 03:35:13 PM
BigBlockChev's Avatar
BigBlockChev BigBlockChev is offline
Subscriber
 
Join Date: Jan 2007
Location: Coquitlam, BC, Canada
Posts: 1,800
Thanks: 311
Thanked 1,323 Times in 776 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

It is a little hard to tell but it looks like a magneciter control box. The YD control boxes have 4 more wires coming up in the corner and going to the VR penthouse. The mag sets only have one wire going to the field flash connection on the mag terminal strip. I think the "1985" may be a red herring. A picture of the end of the generator would be helpful and definitive. Cheers Dan
__________________
It's always something simple.
One test is worth a thousand guesses.
If some is good and more is better then too much is just enough
Reply With Quote
The Following User Says Thank You to BigBlockChev For This Post:
  #33  
Old 08-06-2017, 08:20:23 PM
sscummins sscummins is offline
Registered
 
Join Date: Jul 2017
Location: Federal Way, Washington
Posts: 37
Thanks: 27
Thanked 4 Times in 2 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Hi everyone, been busy keeping wife and daughter happy, so i was able to sit here now at the mall and log in, not my favorite place to be lol, any way not looking to close before, but it has i think 4 wires coming out of the genhead, i will verify when i get home, if,,,,,,lol, i dont know how to tell the difference between an exciter or the other kind, maybe some can explain, i am a mewwwwby at this, my first genset guys, be gentle, i will take some pics of the gen head so you can tell what i have, anyone else need some info????thanks again allof you,,,,much appreciated

Max, my box is a little fuller than ur pics , i have a heater solonoid also, question 4 u any everyone, those 2 tall resistores (i think) the one has wires coatings on both and other has one coated n 1 bare, what r they called on wire diagram n where do they go too? And i take it it has to remain a bare wire for a reason?, thanks

Yeah thats cool, i lve near steel lake park, rt next to it, what a small world,

Sorry that was responce to PnishrPW, and it was sold to me with a radiator small japanese or ?one with an electric fan, dont know if mechanical os better or not? I like mechanical, less fail parts, it was marine setup but changed to non marine, probanly will sell that marine stuff?
Reply With Quote
  #34  
Old 08-06-2017, 08:38:08 PM
nothingbutdarts nothingbutdarts is offline
Sponsor
 
Join Date: Apr 2014
Location: Bailey, Colorado, USA
Posts: 2,118
Thanks: 4,674
Thanked 935 Times in 633 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

If you open the wiring diaghram MBB posted in post # 21 above you will see

R11 and R12, those are the resisrors you are asking about, follow where the wires go in the diaghram.
Reply With Quote
  #35  
Old 08-07-2017, 09:14:49 AM
sscummins sscummins is offline
Registered
 
Join Date: Jul 2017
Location: Federal Way, Washington
Posts: 37
Thanks: 27
Thanked 4 Times in 2 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Click image for larger version

Name:	plate.jpg
Views:	32
Size:	57.9 KB
ID:	288138

Click image for larger version

Name:	exciter.msg.jpg
Views:	29
Size:	148.2 KB
ID:	288139

Click image for larger version

Name:	exciter1.msg.jpg
Views:	27
Size:	130.4 KB
ID:	288140

[ATTACH]288142[[ATTACH]

Ok so I took some pics lasdt night and it has 4 big wires coming from the head to the breaker panel, one of them grounding, there also is a thinner wire coming from or going to the head thats a maybe 12 or 14 gauge wire? anyone know what and where it is supposed to connect to?
I attached the plate from a pic that has info on it about it being an ecxciter with #. someone please advise?

Thanks again
Attached Thumbnails
Click image for larger version

Name:	exciter2.jpg
Views:	30
Size:	56.5 KB
ID:	288142  
Reply With Quote
  #36  
Old 08-07-2017, 09:26:35 AM
sscummins sscummins is offline
Registered
 
Join Date: Jul 2017
Location: Federal Way, Washington
Posts: 37
Thanks: 27
Thanked 4 Times in 2 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

sorry, the thinner wire is going to inside the control box .

alsao I have a wire that is in the box that starts from the emergency relay then terminal block and that wire goes to the sideof the motor not connected to anything, the end of it has a broken off brass connector like the oil pressure sensor and screw is still attached. where does this wire attach to or supposed to attach? Any and all feed back is very very much appreciated ...
Reply With Quote
  #37  
Old 08-07-2017, 04:20:26 PM
BigBlockChev's Avatar
BigBlockChev BigBlockChev is offline
Subscriber
 
Join Date: Jan 2007
Location: Coquitlam, BC, Canada
Posts: 1,800
Thanks: 311
Thanked 1,323 Times in 776 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Ok so it is a magneciter machine, it was not made in 1985 but 1973 or earlier. A pic of where the two unknown wires come from and where they end up would be helpful to determining what they are supposed to connect to. Cheers Dan

The thinner wire coming from the head to inside the control box is likely the 12V automatic field flash lead. It should connect to the exciter terminal strip , I believe it is numbered 35 or 38 on the exciter. You should ohm out that wire from the terminal strip to inside the control box to be sure. It's purpose is to flash the field when the starter is engaged to ensure there is a good residual magnetic field to enable the generator to start generating. You will have to remove the end cover on the generator head to get access. Once again many pics are a big help for us to be able to assist you in figuring things out.
__________________
It's always something simple.
One test is worth a thousand guesses.
If some is good and more is better then too much is just enough
Reply With Quote
The Following User Says Thank You to BigBlockChev For This Post:
  #38  
Old 08-07-2017, 06:30:03 PM
sscummins sscummins is offline
Registered
 
Join Date: Jul 2017
Location: Federal Way, Washington
Posts: 37
Thanks: 27
Thanked 4 Times in 2 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Will do Bigblockchev,

I will check things out if I get home before dark. to much work.

Thank you.
Reply With Quote
  #39  
Old 08-07-2017, 11:28:02 PM
sscummins sscummins is offline
Registered
 
Join Date: Jul 2017
Location: Federal Way, Washington
Posts: 37
Thanks: 27
Thanked 4 Times in 2 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Hi bigblockchev,
Ot is #35 tagged and it ohms to the best i can do it to abou3_17 ohms depending on the grip, now that is 1 wire without a mate on terminal block in contrl box, now i see another thinner wire coming into cntrl box from under it (assuming it looks to go into genhead? Ithink) and it goes from gen head to terminal blck and mates to wire that goes to starter solonoid oppsite side of b+ cable,? The other mistery wire coming from term blk ends with a eye crimp for a screw to attatch it. I thought before it had an end like oil pressure sensor but no it doesnt, see pic below in the morning when i get to work and down load pics. Frpm diagram it calls for it to go to fuel pump and then to relay emergency lop, and all i see is mechanical pumps???? Upload pics in the am
Reply With Quote
  #40  
Old 08-08-2017, 12:12:15 AM
nothingbutdarts nothingbutdarts is offline
Sponsor
 
Join Date: Apr 2014
Location: Bailey, Colorado, USA
Posts: 2,118
Thanks: 4,674
Thanked 935 Times in 633 Posts
Default Re: Onan 12 MDJC - 3r/2268d (1985)

Maybe the one wire with the eyelit on the end goes to the fuel pump shut-off solenoid?
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

F o r u m Jump

Similar Threads Chosen at Random
Thread Thread Starter F o r u m Replies Last Post
Onan L3179-M 1985 15 KW Deisel hurdy Onan Generators 4 07-26-2012 07:54:30 PM
Onan 12MDJC-3r/2268d 120 output only? Tburk49760 Onan Generators 5 12-07-2011 10:36:21 AM
Onan 12 KW 12.O MDJC-3CR Jasonl007 Onan Generators 7 07-23-2010 12:18:35 AM
Onan 12.0 MDJC Doug101 Onan Generators 2 03-26-2008 06:25:53 PM
Onan 6.0 DJB-3CR C spec 1985 yr - Getting to run DCWatmough Onan Generators 4 10-24-2005 11:04:14 PM


Use "Ctrl" mouse wheel to change screen size.
All times are GMT -4. The time now is 03:28:22 PM.

Smokstak and Enginads site search!


All use is subject to our TERMS OF SERVICE
SMOKSTAK® is a Registered Trade Mark - A Community of Antique Engine Enthusiasts
Copyright © 2000 - 2016 by Harry Matthews P.O. Box 5612 - Sarasota, FL 34277