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Quick help with Onan 12.5


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  #1  
Old 03-10-2017, 10:11:53 AM
Handyhiker1 Handyhiker1 is offline
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Default Quick help with Onan 12.5

Going to look at an Onan 12.5 4 cyclindee has generator. I assume it is a 12.5 JC. I do not know anything about these units so I am asking advice. What trouble areas to look for? Other then standard stuff, any unusual checks I should make?

Thanks for any info, sorry I have no numbers for this unit.

---------- Post added at 09:11:53 AM ---------- Previous post was at 09:10:35 AM ----------

Let's try this, 4 cylinder gas engine.
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Old 03-10-2017, 11:14:23 AM
Max Thompson Max Thompson is offline
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Default Re: Quick help with onan 12.5

Going out to look at it because???

It wont start? Wont run? Wont make elec.?

I would take the YD service manual #900-0184 and JC service manual #967-0500 along with me.

If it is 12.5 KW and 4 cylinder, my money would be on a J series.
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Old 03-10-2017, 11:19:15 AM
Handyhiker1 Handyhiker1 is offline
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Default Re: Quick help with onan 12.5

The price is right.
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Old 03-10-2017, 11:35:42 AM
Ray Lynch Ray Lynch is offline
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Default Re: Quick help with onan 12.5

Quote:
Originally Posted by Handyhiker1 View Post
The price is right.
Phase and voltage meet your needs?
Ray
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Old 03-10-2017, 11:38:13 AM
Max Thompson Max Thompson is offline
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Default Re: Quick help with onan 12.5

I misunderstood, I thought you were going out to repair it.

Things to check:

Look in the control box for rodent damage or hack jobs on the wiring.

Be sure the engine will turn over and is not locked up.

Is the starter, carb and all cooling tins included.

This is a very short list. If the price is right (scrap price) you can always part it out if it doesn't pan out.

Just for fun, take some pictures and get the data tag info even if you do not buy it.

If the price is right
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Old 03-10-2017, 11:58:00 AM
Handyhiker1 Handyhiker1 is offline
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Default Re: Quick help with onan 12.5

Quote:
Originally Posted by Ray Lynch View Post
Phase and voltage meet your needs?
Ray
Don't know. This is a total unknowns unit. I will look though.
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Old 03-10-2017, 03:52:13 PM
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Default Re: Quick help with onan 12.5

I bought the generator. Here is a pick of the tag. Getting it delivered tomorrow morning.
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Old 03-10-2017, 04:09:57 PM
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BigBlockChev BigBlockChev is offline
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Default Re: Quick help with onan 12.5

You won't be sorry. Most frequent issue with J series YD genend sets is the voltage regulator which can be replaced cheaply or with a more expensive regulator. If it runs and generates you are golden. Cheers Dan
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Old 03-10-2017, 06:12:02 PM
Handyhiker1 Handyhiker1 is offline
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Default Re: Quick help with onan 12.5

Well it does not run so I don't know about producing power. It is complete from what I saw and I was able to spin the engine by hand. There is a mouse nest in the control box but I don't know how much damage they did.
I will do some checks on it tomorrow when it gets delivered.

I am sure I will have questions since I have never even seen this model in person let alone worked on one. I will grab some pictures and post them when I get it.
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Old 03-10-2017, 07:35:54 PM
Max Thompson Max Thompson is offline
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Default Re: Quick help with onan 12.5

I assumed you had bought it when I saw the listing had been deleted.

In my "opinion" (for what it is worth) the JC sets are very easy to work on because of their size and design. They are large enough that components are not jammed into a small inaccessible place, yet small enough to move around on a cart by yourself. The controls are very simple, and as mentioned all the high $ OEM electrical parts can be replaced with aftermarket parts very reasonably.
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Old 03-10-2017, 08:04:08 PM
Handyhiker1 Handyhiker1 is offline
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Default Re: Quick help with onan 12.5

I am excited to get this, it is the largest both size and output that I have ever had. I know it won't be fuel efficient but it will be neat to play with. I really don't need one this big, just couldn't pass it up. I may get it running and working and then look to sell it. Have to wait and see.
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Old 03-10-2017, 09:15:47 PM
Ray Lynch Ray Lynch is offline
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Default Re: Quick help with onan 12.5

Quote:
Originally Posted by Handyhiker1 View Post
I am excited to get this, it will be neat to play with. .
Yes it will...have fun.
Ray
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Old 03-10-2017, 10:34:44 PM
JohnnyC JohnnyC is offline
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Default Re: Quick help with onan 12.5

Congrats on your JC purchase. The mouse is almost a guaranteed non-desirable option that comes with the J series Onans although Onan does not have an option code for them.

JohnnyC
New Jersey
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Old 03-10-2017, 11:04:33 PM
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Jim McIntyre Jim McIntyre is offline
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Default Re: Quick help with onan 12.5

^ Yep the cheese-covered control wiring and rodent revolving door in the control box were actually standard fittments - not an option at all...
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Old 03-11-2017, 03:00:43 AM
Ray Lynch Ray Lynch is offline
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Default Re: Quick help with onan 12.5

This rare photo of an Onan Design Engineer hard at work on the computer explains a lot of the rodent related problems with these sets.
Ray

http://4.bp.blogspot.com/-WWN2jvTnHr...tures+(13).jpg
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Old 03-11-2017, 07:14:52 AM
Handyhiker1 Handyhiker1 is offline
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Default Re: Quick help with onan 12.5

Here is the picture of what the seller posted. It actually looked a little better in person, not a lot but a little. :-)
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Old 03-11-2017, 07:53:16 AM
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Default Re: Quick help with onan 12.5

Quote:
Originally Posted by Max Thompson View Post
Going out to look at it because???

It wont start? Wont run? Wont make elec.?

I would take the YD service manual #900-0184 and JC service manual #967-0500 along with me.

If it is 12.5 KW and 4 cylinder, my money would be on a J series.
Are these the only 2 manuals I will need for this unit?

Another question, I noticed that some of these units seem to be forced air cooled and some are vacuflo cooled, any real difference? I would assume this had to do with the way it was mounted. I was told this one was in a motor Home so that is why the vacuflo system.
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Old 03-11-2017, 11:43:58 AM
Max Thompson Max Thompson is offline
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Default Re: Quick help with onan 12.5

Those 2 manuals will answer most of your questions. The service manual covers the engine and most of the control system. The YD manual covers the generator end.

The vacu-flow sets allow the cooling air to be "directed / ducted" much more easily than the pressure cooled units.

I am finding the vacu-flow set much more covenant to "work on", because the side of the engine with the distributor, carb and governor is open and accessible while the engine is running. On the pressure cooled sets, these items are all behind the cooling tin that must be in place while the engine is running which requires removing and reinstalling the tin with each "adjustment" if the engine is going to be run for more than just a few minutes.

The exhaust side is a little more difficult to access, but not much to do over there.
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Old 03-11-2017, 02:41:50 PM
Handyhiker1 Handyhiker1 is offline
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Default Re: Quick help with onan 12.5

Oh my!! I just discovered something bout the generator, it is a factory duel fuel!! It has the gaseous directions and intake maniold as well as gas. I didn't even realize it at first.
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Old 03-11-2017, 02:43:37 PM
Handyhiker1 Handyhiker1 is offline
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Default Re: Quick help with onan 12.5

A few pictures.
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