HOT COIL

put my super M on 12volts 1 wire delco and the 9 yards now after a min. of running coil gets VERY HOT tractor runs very well not sure what the deal is any help from you old timers would be great thanks

Is your farmall Super M came stock with a 12 volt system. When converting over to a 12 volt system is most likey to put a resister wire set up from ignition key to coil wire. This will help you not burning the wires or the points on the dist. If the coil continues to be hot durning running time it is the secoundary coil winding in coil and should be replaced with a new one. This should fix your problem.

Did you switch coils from six to twelve volt? Or you can get a ceramic piece that cuts the voltage down. Maybe called a resistor? Anyway that lowers the voltage so it won't cook your six volt coil.

If u used a coil marked 12 v , the excess voltage is burned off using a internal resister , so that in effect the coil is using 6v . this produces heat (ALL COILS USE 6V TO PRODUCE THE SPARK ENERGY)
Yes they do get hot. How hot? depends on many things!

Well no flame here just fact. No modern coil has internal resistors. The windings are designed to run at 14.2 to 14.8 volts. There are more turns on the primary, and finer wire. The coil made like this is marked 12v no external resistor required. Coils designed to operate with an external resistor, or on 6volt systems, are basically the same. Both type draw about 3 to 4 amps when turned on (points closed) The reason for the ballast resistor is to allow a bypass circuit to give starting voltage directly to the coil when cranking. this allows hotter spark and while cranking the battery voltage can drop to 10 volts or less. This topic has met the same fate many times here so don't feel bad, just run with the new info. Jim

"the excess voltage is burned off using a internal resister"

Dear LORD! Didn"t know it was time AGAIN for that "old mechanic"s wive"s tale!

The secondary carries very little current at a high voltage so it doesn't heat up. It does get hot from the primary that is carrying too much amps.

Lots of misinformation here. Let me start out by saying I think you are using the original coil (or one intended for use with an external resistor). The original "six volt" coil is going to run hotter than a "12 volt no external resistor" coil because there is more current running through the six volt coil. So you probably need to either replace your coil with a "no external resistor" coil or add a ballast resistor. From a functional point of view it makes no difference which you do, although it's a lot simpler to change out the coil. Any decent auto parts store will carry a generic coil for this purpose.

It is not true that a so-called "12 volt" (no external resistor) coil is better than a "6 volt" coil plus external resistor combination, even though it as been repeated as gospel here so many times I've lost count. What's the difference between a coil that requires an external resistor and one that doesn't? It should be obvious: the latter has a higher internal resistance! How the resistance is added is irrelevant, whether it's done using smaller gauge wire in the primary winding or some sort of resistor inside the coil. (I think it's the former, but it really doesn't matter.) The inductance of the two coil types is identical, so the only difference is internal resistance. In fact, from an electrical point of view, it doesn't matter whether that resistance is inside or outside the coil. The "no external resistor" coils are easier to install than an external resistor, but in no way do they provide any better spark.

Why have a resistor at all? The added resistance does two things: First, it reduces the current through the points. Second, it adds damping to the circuit so the voltage transients that occur when the points open decay faster. Together, these effects make the points last longer. And, as you've discovered, the coil doesn't get as hot.

A case can be made for resistor plus coil vs 'true 12v coil" with adequate intrinsic resistance to require no external resistor. That being, that the coil with external resistor will run cooler, since part of heat load is in coil & part in external resistor, whereas, with "true 12v coil", the coil must handle the combined heat of coil plus the heat that was formerly dissipated in external resistor. Obviously not terribly important as they survive the additional heat! HOT? To your hand? Sure, mounted to engine at 150 plus, combined with its own heat, it is happy, even at 200 degrees.

(quoted from post at 09:58:42 08/21/13) A case can be made for resistor plus coil vs 'true 12v coil" with adequate intrinsic resistance to require no external resistor. That being, that the coil with external resistor will run cooler, since part of heat load is in coil & part in external resistor, whereas, with "true 12v coil", the coil must handle the combined heat of coil plus the heat that was formerly dissipated in external resistor. Obviously not terribly important as they survive the additional heat! HOT? To your hand? Sure, mounted to engine at 150 plus, combined with its own heat, it is happy, even at 200 degrees.

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The other advantage to using a separate resistor is it allows you to bypass the resistor and and apply cranking voltage to the coil when starting. In instead of lowering the voltage at the coil during cranking it raises it to provide more voltage available to the secondary circuit.