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Super, You ask if your 12 volt tractor should have a Ballast Resistor and the correct answer is IT DEPENDS, heres the real deal: A 12 volt tractor needs EITHER: a) A full true 12 volt coil (some call internally ballasted) OR b) A 6 volt coil with an added external series voltage dropping (12 to 6) Ballast Resistor wired AFTER the Ignition Switch but BEFORE n ahead of the Coils input (NOT to distributor) terminal. Note thats wired in series with and before the coil NOT paralell across its terminals Nowwwww ww a full true no ballast required 12 volt coil may be labeled "12 volts" or "12 volts NOT for use with external ballast resistor" HOWEVER if its labeled "12 volts for use with (or requires) an external ballast resistor" its in reality a 6 volt coil and indeed does require the ballast just like it says on the label. Next if its not labeled heres how to tell: A 6 volt coils primary resistance as measured between its lil + and - terminals is around 1.25 to 2 ohms while a 12 volt is more like 2.5 to 3.5 ohms. If a coil runs so hot you can barely lay your hand on it theres a good chance its an unballasted 6 volt coil on a 12 volt tractor which will also cause the points to burn up very soon and badly. Last NOTE: A coil runs more efficient and will deliver more spark energy if its wired at the correct polarity: For a neg ground that means its lil + is wired to the ignition switch while its lil - wires to the distributor. For Pos ground reverse that. Hope this helps. John T in Indiana
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