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Thread: ballast resistor ?

  1. #1
    Join Date
    Apr 2009
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    Las Vegas, NV.
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    Default ballast resistor ?

    Does a 79 Scout have a ballast resistor? I am having a problem with my 79 Scout II where it will run and then after about 10 minutes it will die and will restart after about 10-15 minutes. I have changed the distributor and coil, I need to rebuild the carb, I have already replaced the fuel pump and filter. I am going to do a small block chevy converson down the road but need to get running now. any help will be appreciated.

    Earthquake

  2. #2
    Join Date
    Feb 2009
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    Aiken, SC
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    Default

    Quote Originally Posted by earthquake View Post
    Does a 79 Scout have a ballast resistor? I am having a problem with my 79 Scout II where it will run and then after about 10 minutes it will die and will restart after about 10-15 minutes. I have changed the distributor and coil, I need to rebuild the carb, I have already replaced the fuel pump and filter. I am going to do a small block chevy converson down the road but need to get running now. any help will be appreciated.

    Earthquake
    No ballast resistor. They don't tend to fail in this manner anyway. They usually just die, although a crack in one could cause an intermittent connection.

    The 79 has a prestolite module inside the distributor that uses a full 12 volts, which also feeds the (+) coil terminal. If you changed it out already, what did you use as a replacement?

    Common causes to this problem are:

    Module failing.
    Wire grounding out as engine warms up.
    Bulkhead connector loose.
    Coil failing.

    In a points ignition, which you should not have, but still might, you sometimes find the wire from the condensor has rubbed the insulation off, and there is an intermittent ground. It is also common for the condensor to fail due to heat for the same reason, but more often, heat causes the coil to fail, and the condensor just dies altogether.
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

  3. #3
    Join Date
    Apr 2009
    Location
    Houston
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    Default

    Quote Originally Posted by Allan E. View Post
    No ballast resistor. They don't tend to fail in this manner anyway. They usually just die, although a crack in one could cause an intermittent connection.

    The 79 has a prestolite module inside the distributor that uses a full 12 volts, which also feeds the (+) coil terminal. If you changed it out already, what did you use as a replacement?

    Common causes to this problem are:

    Module failing.
    Wire grounding out as engine warms up.
    Bulkhead connector loose.
    Coil failing.

    In a points ignition, which you should not have, but still might, you sometimes find the wire from the condensor has rubbed the insulation off, and there is an intermittent ground. It is also common for the condensor to fail due to heat for the same reason, but more often, heat causes the coil to fail, and the condensor just dies altogether.
    Don't forget my scout had the same problem and I never thought it had points but it did. Some previous owner replaced the electronic prestolite with a points prestolite and didn't add an ignition resistor. That ruined the points and the coil. Before I figured it out the new coil made it run better but ruined the points even more. How many wires are coming from the distributor?

  4. #4
    Join Date
    Feb 2009
    Location
    Aiken, SC
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    2,423

    Default

    If a coil fails, it can fry the points. That would be a shorted coil, of course. An open coil primary will not burn anything else out.
    Full voltage to the coil is not enough to fry it if your cap, rotor, plug wires, and plugs are in good shape. You can run Jacobs or MSD from a stock coil with no problem. Some of the "hot" aftermarket coils will not work without a ballast resistor. If you cut the primary voltage in half, you cut output power by 75%. It is better to have a coil with a 3 ohm primary if you don't have a ballast resistor, assuming all the resistance is in the coil.

    Full voltage will fry the points. Saving the points is the only function of the ballast resistor.

    Shorted (non-opening or shorted to ground) points will fry a coil as well. The heat keeps building with no place to go, and all the power is dissipated inside the coil rather than pushed out to the spark plugs.
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

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