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  1. #1
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    Default 12 volt conversion

    Okay so I did the 12 volt conversion on my 800 series tractor. The issue I'm having is there doesn't seem to be enough juice making it to the coil to start it. I can run a hot wire from the switch to coil{bypass resistor} to get it running then unhook the hot wire and it runs fine. If I try to start it by just using the resistor it won't fire. I did by another coil {internal resistor} but it still has the same issue. While the starter is cranking it doesn't seem to have enough juice to power the coil, an ideas? Thanks

  2. #2
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    Default Re: 12 volt conversion

    I believe that vehicles with coils are wired so the resistor is bypassed while cranking, then the coil is powered through the resistor once the engine is running.

    When the resistor died, Old Mopars would famously start right up, then quit as soon as you released the key to the run position.

  3. #3
    Old Timer Soundguy's Avatar
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    ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC

    Default Re: 12 volt conversion

    need to know what resistor you have and what coil you have.

    I seriously dooubt you got a coil that claims it has an internal resistive element. coils today are simply produced with the correct diameter and length of the primary winding to produce the impedance requird ont he coil primary.

    A coil like a napa IC14SB is 16$ and needs no external resistor.

    how old is the ignition switch and how do the electrical connections look?

    for a 12v system you want 3-3.5 ohms of primary resistance..

    I personally would get rid of the power wasting resistor and get a real, native 12v coil like the IC14sb

    soundguy

    soundguy

  4. #4
    Old Timer Soundguy's Avatar
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    Default Re: 12 volt conversion

    Quote Originally Posted by Travelover View Post
    I believe that vehicles with coils are wired so the resistor is bypassed while cranking, then the coil is powered through the resistor once the engine is running.

    When the resistor died, Old Mopars would famously start right up, then quit as soon as you released the key to the run position.
    the NAA certaintly did NOT leave the factory with a bypass relay setup on the igntion.

    it was 6v when oem, and used a 6v coil and no resistor.

    soundguy

  5. #5
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    Default Re: 12 volt conversion

    Quote Originally Posted by Soundguy View Post
    the NAA certaintly did NOT leave the factory with a bypass relay setup on the igntion.

    it was 6v when oem, and used a 6v coil and no resistor.

    soundguy
    The systems I am familiar with on older cars don't use a relay, they are simply wired so the coil gets 12 volts directly during cranking (as does the starter solenoid) and 12 volts to the coil resistor in the run position. It seems like the OP is saying that this scheme works when he hot wires it to achieve the same result.

  6. #6
    Old Timer Soundguy's Avatar
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    Default Re: 12 volt conversion

    you might want to brush up on your electrical terminology.

    the relay I spke of is the starter solenoid.

    4 terminal 'bypass' styel solenoids are common... when the starter solenoid ( RELAY ) is energized, it not only energizes the starter but sends bat power to the coil, "BYPASSING" any ignition resistors in line.

    as I stated before , the NAA DID NOT use any sort of bypass style solenoid (RELAY ) in it's original scheme.. and it was 6v using a 6v coil.. thius no ignition resistor needed anyway.

    soundguy

  7. #7
    Elite Member BobRip's Avatar
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    Default Re: 12 volt conversion

    Quote Originally Posted by Travelover View Post
    The systems I am familiar with on older cars don't use a relay, they are simply wired so the coil gets 12 volts directly during cranking (as does the starter solenoid) and 12 volts to the coil resistor in the run position. It seems like the OP is saying that this scheme works when he hot wires it to achieve the same result.
    I think with that design the relay would be paralleled with the starter and the starter would ground out the resistor when not cranking. This assumes the resistor it tied to the positive side of the coil.
    Bob Rip
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    Show me and I will see.
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    Let me fail and I will understand.

  8. #8
    Old Timer Soundguy's Avatar
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    Default Re: 12 volt conversion

    this isn't hard guys.

    it's a 4 post relay

    1 post from the bat, 1 post to the starter, one post from the spring loaded start position on the key ( switched 12v ) and one post to the coil side of the resistor.

    when the post from the key is powered, the other small post is fed 12v as well, which ithen feeds 12v to the coil, thus BYPASSING the resistor. at the same time the 2 large contacts are closed so bat is fed to starter.

    no rocket science.. just electromechanical switches. think of a DPST set of contacts with a single common feed ( yet seperate isolated outputs ) one oputput to starter.. one to coil.. seperate switches, so after starting the starter is not loading the ignition ckt.

    soundguy

  9. #9
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    Default

    Quote Originally Posted by Soundguy

    the NAA certaintly did NOT leave the factory with a bypass relay setup on the igntion.

    it was 6v when oem, and used a 6v coil and no resistor.

    soundguy
    Seems to be 12v w/ a resistor now

  10. #10
    Platinum Member Army grunt's Avatar
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    Default Re: 12 volt conversion

    Put a wire (#12) on the starter pole an bypass the resistor. when you hit the starter it will give 12 volt right to the points.When you let off starter it will see the resistor voltage, an save your points.
    Army Grunt
    "Be who you are, say what you will, those that matter wont mind, those that mind don't matter".

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