How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Hank F. Your Own Question
Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14890
Experience:  Certified on Onan and Generac generators
Type Your Small Engine Question Here...
Hank F. is online now
A new question is answered every 9 seconds

need schematic for onan generator

Customer Question

need schematic for onan generator bought unit off ebay, and it looks like a device /relay is missing out of a 8 pin socket. model 15 jc-4rv 31/ir serial number 127c998544. 1985 would be a guess for vintage. help identify possible correct manual off ebay or other would be helpful.

I might think that the missing device coud be for a voltage regulator for charging up the battery. stated doing a schematic but did not complete it. thanks. this is a 50 amp three phase package. thanks for your input and direction
Submitted: 6 years ago.
Category: Small Engine
Expert:  Hank F. replied 6 years ago.


Your set was actually produced in December 1967.


There are many variations of the JC set.


Inside your control box is a terminal strip. Does yours have 8 slots or 10?

If yours has 10, there will be 2 relays present. Does yours have one or none?


If you have one, what are the wire numbers that go to it, and what are the wire numbers that go to the empty socket?


Customer: replied 6 years ago.
two relays the first relay goes to coil wires terminal 7 and 11 and what got me as kind of odd is it is 24v coil. terminal 9 and 5 for NC,c. I will get the wire numbers for what is the 8 or 10 pin round socket, I know that it has 6 wires connected but will continue to draw up. just turned 52 last week and have to laugh at 67 is young, the x was born in 77. That joke is on me.
Expert:  Hank F. replied 6 years ago.

While you are at it, could you also rep-check the model number? The 31 does not seem right, and the ir should actually be 1R?

Also, on the data plate, or a sticker on the inside of the control box cover, does it list a wiring diagram number?


Edited by Hank F. on 9/25/2010 at 4:17 PM EST
Customer: replied 6 years ago.

the gen is off site and After the kids soccer i will reviewedmy notes have a couple of other reference number

excher 065xiv3b bat 12

gen data 15jc4n40

Expert:  Hank F. replied 6 years ago.

Sorry, but those numbers will not help us.


Customer: replied 6 years ago.

echanger 3 is 06sx1n3b number on electrical plant is 15JC-4RV 31/1R

It is an 8 pin socket with 6 pins being used.

1. ground

2. front panel swith for manual or electrical crank

3. small plate in box hard to see with possible a rectifier

4 front amp meter

5 to resister and then to start stop switch

6 termianl wire number 10or 11


no wire numbers located on wires. all other wires have numbers and it seems like an origional set up.


if i had a good typical drawing and a regulator i think i could rewark. thanks unless I'am missing somthing.


I would guess the missing device is for the regulator for charging the battery a relay do not see a regulator unless it is more to the plate that stands up and down that is hard to see.

Expert:  Hank F. replied 6 years ago.


Here is the latest, greatest lowdown showdown.


This set is almost as old as I am (I was still in diapers when this set was built).

Remember when I said the '31' in the model number did not sound right?

Well, it is. I found an obscure reference to it in my files.

The 31 denotes that this was a special-order set, and is Pennsylvania approved. There are several parts on this set that are not found on the standard JC's, and several parts that are different than standard.

These 2 relays are only found on the PA - approved sets. My parts books do show them, and they both show as still available.

However, I do not have access to special order schematics. None of the standard schematics show these relays.

I do have a good friend who may, though. But we will need to figure out which schematic it is.

Somewhere on the set - either on the data plate, or on a sticker inside the control box cover, it should list the schematic number. It may say diagram, schematic, or drawing.

Can you find this number?


Of the 2 relays, one is a start disconnect relay, and the other is a field build up relay.

Due to the fact that most of your wires go to meters or controls, I would suspect the one you are missing is the field build up relay.


The voltage regulator in your set is a large PC board. Is this the 'panel' you are seeing?


Customer: replied 6 years ago.

I will take pictue of the two id plates on the system and have another look. remember that in the 60's we went to the moon and the controls on this things where about the same vintage. I like that termonalogy "field build up relay" I watch a national geographic special on the world running out of oil. And my daughter wanted to get on tv and tell people that we are going to run out of oil and she wanted to know if we could build a force field around michigan, but wanted to know how we would get water. I will tell her we need a "field build up relay" or could i call it a 10 dollar regulator. I think the new space program is using the same modified rockets from the 60, but they are going a little more modern with the control. might be logical. the concept of using somthing that was pen approved in the 60's is possible the reason that this thing was on ebay. as a back up do we have a standard schematic. not building a rocket ship, or am I. thanks have to get the kids off to school or they will watch spung bob all day. dave


Expert:  Hank F. replied 6 years ago.

Here is the standard schematic.

Click here.


When the 4shared page opens up, click on the blue 'Download Now' button.


Hank F. and 2 other Small Engine Specialists are ready to help you
Expert:  Hank F. replied 6 years ago.

My friend is still checking on the specific schematic for your set.


Expert:  Hank F. replied 6 years ago.

My friend and I have both looked up this model and serial number, and they are not matching according to Onan's records.

This serial number came up showing 4 different sets - 4CCK, 6.5NH, 5GO, 6JB - but no 15JC.


Is there any chance you have a number or 2 switched, or possibly mis-read?

On old tags that are beaten and scratched, it is easy to confuse 6, 8, and 9.



Customer: replied 6 years ago.

serial number is XXXXX it is perfect clean.

approval # XXXXX

exhganger O OR 06SX1N3B

gen data 15jc4N40


the unit was sold by MIL-Penn 115 w norweigian st pottsville penn.


I will sign off on this one and keep digging if you can, should i open Another question.


I do not have a board in this unit. The schematic looks the same for the jc air cooled with the exception of the baord is exchanged with the 8 pin device. can I get a board. possible the direct appoach.

Expert:  Hank F. replied 6 years ago.

According to my friend, the relay with the round base is the start disconnect relay.

It is part number(NNN) NNN-NNNN It is available from Onan for about $55.


The other relay is the field build up relay, and is part number(NNN) NNN-NNNN It is also available - for about $260.


You can find your nearest authorized Onan dealer by going to and entering your ZIP code.


We were unable to find the actual schematic for your set. Onan Corp. sold out to Cummins Inc. back in the mid 80's. A lot of information was lost in the transfer. I am sure the schematic is available, if we could just find the schematic number.

I will keep looking.


Customer: replied 6 years ago.

thanks, so your manual had a lot of infomation, it looks like i'am missing the board and, they have the four wires out of the generator going to a lower box and that is it. So if you want to tell me what I need and how much, (how much to tell me how much) iam game other wise i think i have to diagest what iam missing and i would guess the relay should just fall into place.

I have been doing remanufactured equipment for the semiconducor industry specializing in a couple product lines make over 25 years, last week we pulled out a box of over 50 wiring harnests (hornet), kind of laughed and trying to think what happended to the rest of the tools. more boxes to go.

Expert:  Hank F. replied 6 years ago.

It could take weeks to go back and forth to see what is there and what is missing.


How about if I just supply you with the parts manual for this set?

Make sure to pay attention to the Special Parts section at the back of the manual, as well the build codes a the front of the manual.

Your set is a Spec R, so make sure you are looking at the appropriate pages.

Click here to download the manual.


Only use this manual for parts identification. Do not rely on the part numbers, as Onan is really bad about changing part numbers.

If you have a question about a specific part, I can look up the number to check for current numbers, as well as availability and approximate cost.


Expert:  Hank F. replied 6 years ago.


I found that your set does not have a board in it.


I contacted my friend, who contacted his, and so on - and have come up with the schematic for your set.

The reason this was so hard to find is that yours is the only set built to this spec - the only one in the world.

I also managed to get a little extra information for you, that you might be interested in having for this very, very rare set.


As above, when the 4shared page opens, click on the blue 'Download Now' button.

Click here for the copy of the original build card (the original order card).

Click here for the copy of the exciter diagram.

Click here for the AC schematic (the one you have been looking for).