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Thread: Off topic unless CAT made a welder.....

  1. #1
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    Default Off topic unless CAT made a welder.....

    I'm working on an old Onan powered Lincoln welder. I had trouble keeping it running last year and I finally got to it on my list of things to fix.

    I believe it has a magneto to produce spark. I didn't want to invest in a new mag or tools to get to it. So, I bought a dual lead ignition coil for such a motor and plan to use the standard Onan points to trigger the coil. ( the points are in a seperate location from the magneto.)

    I need to run 12V to my coil an and to my points. The welder has a 24V starter and uses 2 12V batteries.
    I cannot find 12V anywhere on this welder to tie in for my new ignition source. Either battery positive is 24V when all is connected.

    How to drop 24V to 12V for my new ignition coil and points conversion ?

    Thanks in advance to the smart people.

  2. #2
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    Two 12v battery in series for 24v means that you can get 12v from the positive battery terminal on the grounded battery. I think
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  3. #3
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    you need a resistor. some coil have an external resistor just get one for 24 volts

    like this one http://www.partdeal.com/stewart-warn...SABEgKTjfD_BwE

    i am not sure that resistor is for enough wattage so check around
    Last edited by bursitis; 11-06-2017 at 08:08 PM.

  4. #4
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    Default

    And Cat did make a welder...
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  5. #5
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    Default

    Quote Originally Posted by TOGNOT View Post

    The welder has a 24V starter and uses 2 12V batteries.
    I cannot find 12V anywhere on this welder to tie in for my new ignition source. Either battery positive is 24V when all is connected.

    How to drop 24V to 12V for my new ignition coil and points conversion ?
    Given that it has two 12 volt batteries it certainly has two combinations of + & - that will give you 12 volts. The one you want is the battery that has a cable connected to the frame. If its negative ground you can use the positive post to feed your ignition circuit 12 volts. Using the other battery that has a cable to the starter or start solenoid is going to give you 24 volts. However that would be the best configuration because it loads both batteries equally. Using only one battery without an equal load on the other one will eventually kill the one supplying the load since it will suffer from chronic undercharge. An ignition resister is the way to go. It is possible the coil needs to get less than 12 volts once the engine starts, so an additional resister might be needed if the starter or ignition switch has a bypass circuit built into it. Many starters or starter relays have an ignition terminal that is used to send full voltage to the coil and points during cranking so the spark is good and hot. Once the starter drops out, the coil gets its feed through the ignition resister(s?) so it doesn't get too hot and to increase points life.

    Many ONAN owners swear by electronic ignition units like pertronix. It might be a good time to make that change.
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  6. #6
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    However you configure the 12V coil with or without ballast resister you want to limit the amperage to 3.5 to 4 amps during normal run otherwise the coil will overheat and/or the points will burn up. Measure the coil primary resistance . If it is not about 3 ohm resistance add a ballast resister to get it there.

  7. #7
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    Thanks, as obvious as it seems - I was able to get only 12v from the advice provided. Still no spark from my "ignition" but I will carry on......

  8. #8
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    Do you have both plugs and wires hooked to the coil during testing? Unlike a distributer/coil ignition setup, the wasted spark 2 terminal coil high voltage circuit is from one plug to the other.
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  9. #9
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    Confused

    I believe that unless there is a serious wiring error, that you will find that a Condenser/Capacitor is needed to assist in the collapse of magnetism in the coil to get a reliable strong spark. It maybe jumping back across the points.
    There was a Thread mid/late summer that delved into this on a Pony Motor conversion (IIRC?). OM ended up posting some really good diagrams in that Thread(again IIRC?)

  10. #10
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    Thanks all. I am using a "transducer " in place of the condenser , to theoretically make the points last longer. I fear I may have fried it with a 1 second shot of 24v.
    I have both spark plugs grounded when testing for spark.
    I will post a wiring diagram later so you can hopefully point out my error(s).
    I'll also search for the pony coil conversion - seems like the same thing I am doing here

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