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Onan Generators

Onan 15.0JC-18R Control Box with Extra Relays


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  #11  
Old 04-10-2018, 12:23:26 PM
zuhnc zuhnc is offline
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Default Re: Onan 15.0JC-18R Control Box with Extra Relays

A leading zero and then the 02, and missing the decimal point, even WITH glasses, is the problem I have. I try to make my decimal points bigger than necessary for exactly that reason. Good luck with renewing the wiring. Easy to troubleshoot and fix with the proper components and a readable schematic and wiring diagram. zuhnc
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  #12  
Old 04-10-2018, 01:02:10 PM
widlin1 widlin1 is offline
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Default Re: Onan 15.0JC-18R Control Box with Extra Relays

The provided schematic was very clear and high enough resolution to print in "poster" mode which took six pages so I can read it without my dollar store glasses. I hope its an easy fix, but I probably will be back with a couple more questions.

Thank you everyone for helping out so quickly after I posted.

I'll figure out how to get some pictures linked and post them.

Jeff
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  #13  
Old 04-10-2018, 07:13:38 PM
widlin1 widlin1 is offline
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Default Re: Onan 15.0JC-18R Control Box with Extra Relays

Let me try uploading a few pictures of the control box as found, cleaned with the three exra relays wired outside the box out, and the three relays on the outside of the box.







The four white solid strand wires, yellow and black wire attached to the small terminal block at the top of the box run and to and from the three relays. The two yellow wire nuts connect the gray wires on the omron relay to the wire slolid wires on terminal blocks B+ and number 1 on the small terminal block. There is a blue wire attached to the blue wire nut that goes to what I think is the relay for the gas shut off and there is an unseen white wire that also goes to the gas shut off valve.

I guess I neeed carefully draw out a schematic for this and compare the factory schematic

Jeff
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  #14  
Old 04-10-2018, 07:33:42 PM
MBB MBB is offline
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Default Re: Onan 15.0JC-18R Control Box with Extra Relays

Quote "I wonder what the difference is between .02 and .020 "

My mistake. I should have known better.
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Old 04-10-2018, 07:51:06 PM
widlin1 widlin1 is offline
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Default Re: Onan 15.0JC-18R Control Box with Extra Relays

I was greatful for the help.

Thanks again

Jeff
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  #16  
Old 04-10-2018, 07:54:23 PM
Power Power is online now
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Default Re: Onan 15.0JC-18R Control Box with Extra Relays

I would remove obvious added wires and relays, and thoroughly clean terminal strips and relay connections. Then you can trace out original Onan wires one by one, restoring them to original terminations, and noting what is missing. When you have it wired "factory", start testing. Probably have to pull most of the original relays and refurbish them.


Tracing out with all those extra wires and relays connected is unnecessarily difficult.
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  #17  
Old 04-10-2018, 08:09:32 PM
Max Thompson Max Thompson is offline
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Default Re: Onan 15.0JC-18R Control Box with Extra Relays

I agree, remove all added white wires. I am going to guess these all went to some remote “controls”. Not sure what the yellow or black wires were for, they do not belong either. I usually wire my gas shut off solenoids to the + side of the coil, not into the terminal strip. With all that gone, it should be pretty simple. The small 4 screw strip in the top of the box is for remote wires (transfer switch connections).

Save the cube relays and bases. If one is a 6-volt coil DPDT, it can be used to replace the open start disconnect / ignition relay. Or you can replace the relay and use the base. A 12-volt coil relay of the same type can be used to replace the starter relay if needed.

Note: the coil on the open relay (K12) is 6-volt, do not jump 12 volts to it or you will toast the coil.
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  #18  
Old 04-10-2018, 08:25:34 PM
widlin1 widlin1 is offline
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Default Re: Onan 15.0JC-18R Control Box with Extra Relays

Power and Max that sounds like a good path forward. I guess the resistor drops the voltage to 6 for the K12 relay. I have to go out of town tomorrrow so it may be a couple days before I get back on this.

Jeff
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Old 04-13-2018, 09:04:14 AM
widlin1 widlin1 is offline
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Default Re: Onan 15.0JC-18R Control Box with Extra Relays

I had some time yesterday and pulled all the extra hardware out which made for nice access.

I disconnected the lead from K11 relay to the starter so that I could flick the start button without energizing the starter motor.

The K11 relay activates when the coil is shorted to ground but the switch that takes +12 volts to the K12 terminal for the points doesn't close.

When the centrifugal switch closes the K12 relay gets 6 volts and closes the switch to take voltage to the ignition coil so that part of the circuit is fine, the motor just doesn't get up to 900rmp with only the starter powering it.

It seams to me that the K11 relay could be replaced with a double throw, double pole normally open relay just by connecting the + pole of battery to one end of the coil and one end of each of the two switches. Is there anything wrong with doing that? the K11 relay doesn't see any high currents.

Thanks

Jeff
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  #20  
Old 04-13-2018, 10:28:11 AM
Max Thompson Max Thompson is offline
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Default Re: Onan 15.0JC-18R Control Box with Extra Relays

https://www.smokstak.com/forum/album.php?albumid=1428

Above is "my" version of relay swap. Yours may vary.
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