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Onan 12.5JC-3CR, Questions, Just purchased


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  #11  
Old 03-18-2017, 10:01:57 PM
Leon N. Leon N. is offline
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Default Re: Onan 12.5JC-3CR, Questions, Just purchased

No that is not correct. There is no generator overload protection built into the control box. The control box only controls the JC engine side of the machine. You must provide your own generator over load protection external to the machine. Need the services of an electrician for this.

BTW! Looks like some one re labeled the remote vs hand crank ( local start) switch as an on/off switch. It must never be left on when the generator is stopped.

And Yes, the hot air discharge will never reach 375 degrees.
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  #12  
Old 03-18-2017, 10:14:31 PM
Max Thompson Max Thompson is offline
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Default Re: Onan 12.5JC-3CR, Questions, Just purchased

Quote:
Originally Posted by oakyone View Post
Sounds like a two wire oil pressure switch should be pretty simple to install along with the overheat switch in the same circuit.

The unit has a solenoid valve between the two propane regulators. (Not sure why it has two, but it runs well.) The right hand switch on the control panel energizes this valve, but the set runs and starts fine weather it's on or off. Curious.
The first regulator is a pressure regulator. The second is the "demand regulator" which is not a "pressure regulator", but a flow regulator. The demand regulator opens with vacuum from the intake manifold through the carb. (I caused a stir awhile back by saying "vacuum from the carb.).

Onan used a one wire N/O pressure switch (close at 15 psi).
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  #13  
Old 03-18-2017, 10:38:53 PM
oakyone oakyone is offline
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Default Re: Onan 12.5JC-3CR, Questions, Just purchased

Leon N.

Why is the remote vs hand crank switch making the solenoid between the regulators click? Is the start stop switch located under the little door in the top end of the housing (not the one on the control panel) a remote start stop? Both of these start and stop the engine whether that right hand toggle is off or on. I'm confused.
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  #14  
Old 03-18-2017, 11:18:56 PM
nothingbutdarts nothingbutdarts is offline
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Default Re: Onan 12.5JC-3CR, Questions, Just purchased

I believe when in the hand crank position, it powers everything to make the generator run so that means, you are putting 12 volts to the gas shut off valve as well as voltage to the coil and points all the time it is in the hand crank position wheter the engine is running or not, therefor if left in hand crank and the engine is not running, you will burn up the points and maybe the coil and you will drain the battery.
When you toggle the start/stop toggle switch to start the generator, it activates everything I mentioned above however when you let off the switch it returns to center, the run relay inside the control box is activated which then keeps the generator running

I do not know anything about the start/stop under the little door, others will chime in on that.

Last edited by nothingbutdarts; 03-18-2017 at 11:29:07 PM. Reason: added info
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Old 03-19-2017, 12:54:34 AM
Leon N. Leon N. is offline
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Default Re: Onan 12.5JC-3CR, Questions, Just purchased

Post 13. That switch on the right should be labeled "electric start" in the upper position and "hand crank" in the lower position. No matter what position that switch is in, you must activate the left side switch to start the JC or even stop the JC. Refer to the owners manual and 967-500. Not sure what you mean by the little door in the top end of the housing? Please show us a picture. sounds like there is a third switch which may be an extension of the start/stop switch you showed in post 8.

Geeze can't sleep. One more thing. That picture you show in post 8 of the output wiring from the generator. make sure the generator power lead T2 is Grounded to the chassis before you apply 12 VDC to crank the JC or you may damage the Magneciter back end. I suspect behind that lower plate I am referring to probably hides the generator power output 4 wires. Good night.

Last edited by Leon N.; 03-19-2017 at 01:15:59 AM. Reason: More info
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  #16  
Old 03-19-2017, 01:12:23 AM
nothingbutdarts nothingbutdarts is offline
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Default Re: Onan 12.5JC-3CR, Questions, Just purchased

Leon, I believe he is asking about the switch under the little door on the rear of his machine, it's the switch shown in the 3rd picture down in his post #8
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Old 03-19-2017, 03:17:18 AM
JohnnyC JohnnyC is offline
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Default Re: Onan 12.5JC-3CR, Questions, Just purchased

Quote:
Originally Posted by Leon N. View Post
Geeze can't sleep.
--- snip ---
Good night.
Same here, can't sleep either. It is 3:13 am. Last pot of coffee was at 10:15 pm and I knew that was too late. No I am paying for it......

Quote:
Originally Posted by nothingbutdarts View Post
Leon, I believe he is asking about the switch under the little door on the rear of his machine, it's the switch shown in the 3rd picture down in his post #8
That is another switch for starting. It is practical especially when the enclosure is shut closed.

JohnnyC
New Jersey
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  #18  
Old 03-19-2017, 07:25:03 PM
oakyone oakyone is offline
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Default Re: Onan 12.5JC-3CR, Questions, Just purchased

Okay, I'll post just the pic with the extra start/stop switch here.

https://www.smokstak.com/forum/attac...1&d=1489887367

It's under the little door at the top.

If that solenoid is supposed to shut off the propane, it's not working. The unit runs well whether it's energized or not. I'll also trace the wires from the switch in question tomorrow.

I'll re-read the manual and try to find out more about the electric start/hand crank. I didn't think the JC had any provision for hand cranking.

---------- Post added at 04:12:47 PM ---------- Previous post was at 04:09:02 PM ----------

That is another switch for starting. It is practical especially when the enclosure is shut closed.

JohnnyC
New Jersey[/QUOTE]

Yes. Is it the same as a remote start switch? Is a remote start switch just wired to the same terminals as the main one on the control panel?

Thanks everyone for the help!

---------- Post added at 04:25:03 PM ---------- Previous post was at 04:12:47 PM ----------

Geeze can't sleep. One more thing. That picture you show in post 8 of the output wiring from the generator. make sure the generator power lead T2 is Grounded to the chassis before you apply 12 VDC to crank the JC or you may damage the Magneciter back end. I suspect behind that lower plate I am referring to probably hides the generator power output 4 wires. Good night.[/QUOTE]

Yes, the main leads are in the box just below the control panel. T1 and T4 each go to one of the fuses in the old school disconnect box. (Above and to the left of the magnaciter.) T2 and T3 are grounded to the chassis in the same disconnect box. I checked that it was wired to match the diagram from the Onan manual and on the lid of the junction box, but I didn't know about the 12 volt damage possibility. Thanks for the tip.
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  #19  
Old 03-19-2017, 07:28:12 PM
Leon N. Leon N. is offline
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Default Re: Onan 12.5JC-3CR, Questions, Just purchased

Wrong! The JC did have provisions for a hand crank starting method. Take a look, for example, at the wiring diagrams on pages 86 & 87 in 967-500.
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  #20  
Old 03-19-2017, 07:40:51 PM
oakyone oakyone is offline
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Default Re: Onan 12.5JC-3CR, Questions, Just purchased

Okay, the lid of the junction box says "CAUTION T2 MUST BE GROUNDED"
Now I get it!

---------- Post added at 04:40:51 PM ---------- Previous post was at 04:29:17 PM ----------

Okay, now I see there is provision for hand cranking. I suppose that could come in handy if you didn't have a way to jump it, or the starter went gunny-bag when you needed emergency power. Now I'll have to shop for a J series hand crank!

I'm going to have to try and get to the bottom of this propane solenoid. It's not shutting the fuel off, if that was it's purpose.
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