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Onan 12MDJC-3r/2268d 120 output only?


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  #1  
Old 12-05-2011, 05:37:49 PM
Tburk49760 Tburk49760 is offline
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Default Onan 12MDJC-3r/2268d 120 output only?

This is a Magneciter 12kw unit.
I have checked and rechecked the output schematics and am pretty sure I have my 4 leads set up correctly to give me both 120 and 240 volt output. no joy! I get 120 from eache hot to neutral, between the hot leads should be 240 but I get nothing. i have t2 and t3 tied and grounded and t1, t4 as hot... I'm thinking that I should separate it so I can test each 120 volt stack as a separate item then what? Seems like they are both making power but in phase as opposed to 180 degrees out?? Any and all input would be welcomed... Thx
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Old 12-05-2011, 07:16:02 PM
Max Thompson Max Thompson is offline
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Default Re: onan 12mdjc-3r/2268d 120 output only?

The 3-R is connectable for 120, 240, or 120 / 240, it sounds like you have it connected for 120V only. I do not have the reconnection diagram, you will need one of the “Smart Guys” for that.
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Old 12-05-2011, 10:13:20 PM
Dave Edmonds Dave Edmonds is offline
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Smile Re: onan 12mdjc-3r/2268d 120 output only?

Sounds like your theory may be correct, but be VERY careful in finding out!! Do some serious measuring with a voltmeter before reconnecting anything. T3 and T4, or T1 and T2 may have been swapped in the genend. I think your idea of disconnecting everything and measuring voltages would be in order; also, make sure you're reading the labels properly. Should be easy to diagnose; just don't let the magic smoke out, and don't grab something that grabs you back.
Dave Edmonds
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Old 12-07-2011, 12:03:46 AM
Tburk49760 Tburk49760 is offline
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Default Re: onan 12mdjc-3r/2268d 120 output only?

Any input as to how I would determine if indeed the gen output leads are mislabeled? The metal tags are pretty clear and the print is still on some of the insulation. There is a wire on the exciter that is disconnected? I will post a pic soon...
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Old 12-07-2011, 10:07:53 AM
Jim Rankin Jim Rankin is offline
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Default Re: Onan 12MDJC-3r/2268d 120 output only?

Magneciter schematics are in the magneciter sticky at the top of this Onan board. It's possible the exciter wire may be causing some problem, but doesn't seem likely to have any effect on your voltage results.

Take all 4 leads loose from each other and arrange them so they cannot touch anything (secure to terminal strip, dry board etc), crank up the set and check voltages between 1 and 4 and 1 and 3. If you get a lot higher voltage between 1 and 3 and very low voltage between 2 and 4, I would try it with 2 and 4 connected as the neutral.
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Old 12-07-2011, 10:36:21 AM
Magnetite Magnetite is offline
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Default Re: onan 12mdjc-3r/2268d 120 output only?

Quote:
Originally Posted by Tburk49760 View Post
Any input as to how I would determine if indeed the gen output leads are mislabeled?
I wanted to check my 4 lead 4CCK-3CR leads. They weren't marked. I did this:
I disconnected and isolated all 4 leads from each other.

Using a meter, I checked for connection between ground (the generator frame) and all 4 leads. Only one was connected to ground, and according to the manual that was M2. I then checked for connection between M2 and the other 3. Only one was connected to M2 with a low resistance - that lead had to be M1. With the gen running, I saw 120V between M1 and M2, as I should.

I then checked to verify there was a low resistance, but not zero, connection between the other 2. There was. That confirmed that they were connected together as the two ends of the other winding. They were M3 and M4. I just didn't know which was which, yet.

I then checked resistance between each and M1/M2. There was no connection between either and M1 or M2. That was a double check to confirm that those two leads - "A" and "B" - floated relative to M1/M2, and they did. If they didn't float, the wrong connection could burn things up.

Since they floated, I was free to connect either to M2. I chose "A", connected it to M2 and cranked up the gen. I measured the voltage between "B" and M1. If the voltage was 240V then A=M3 and B=M4. If it wasn't 240, I would have swapped, measured again to verify that I saw 240V between "A" and M1 and known that B=M3, A=M4.
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