Ballast Resistor Wiring S80 Question

Discussion in 'General IH Tech' started by jlpdemag, Jul 21, 2010.


  1. jlpdemag

    jlpdemag Farmall Cub

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    I replaced the Ballast Resistor today as part of my rewire on my latest S80. I do have a question about the wiring of the Ballast Resistor wiring. Every diagram I have seen shows the Resistor wired as it is below. I don't understand how it is dropping the voltage to the coil this way. I'm sure this is right, it just doesn't look right. Here's what I have on the IGN circuit:

    [​IMG]
     
  2. Jeff Jamison

    Jeff Jamison Lives in an IH Dealership

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    Thats correct,the ignition switch provides 12 volt to the ballast resistor ,witch drops the voltage to the coil,the wire from the solinoid is only energized when cranking and provides 12 volt to the coil for more power for starting.
    Jeff
     
  3. Lowell

    Lowell Farmall Cub

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    When the key is turned to the start position, a full 12 Volts is supplied from the "I" terminal on the starter to the coil because the voltage is not going through the ballast resistor. It is as if the ballast resister is not even there as it is only using the common connection on the ballast resister to feed power to the coil wire. When the key is then turned to the start position, power is no longer coming from the starter "I" terminal. Now the power goes from the key switch to the ballast resister dropping the voltage as it goes through the resister and then on to the coil.
     
  4. jlpdemag

    jlpdemag Farmall Cub

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    OK thanks. I figured the diagrams were right so that's what I duplicated, just didn't know what was going on when. Thanks for the replies.

    John
     

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