why would a 12V resistor start smoking?

Also, is the resistor new?

It's normal for a new ballast resistor to smoke a bit for a while when it's new, when the engine is running. They get very hot, and oils from manufacturing and handling the thing will cause smoke until burned off. Make sure it's well ventilated, too, to allow it to cool.

Resistor smokes with engine OFF and the ignition ON. It heats up and starts smoking.

I did have the valve cover off to lash the valves the other day, and oil may have sprinkled onto the resistor when the engine was running.

I still think it's normal. But you can test this by removing the distributor cap and placing a piece of paper in the points to make sure they're open. Then, check to see if the resistor is still getting hot.

Without knowing what exactly you wired up, I am guessing but I suspect that when you shut down the engine, the gen / alt is not supplying light current and it comes through your ignition circuit. The added load of the lights is overloading the ignition balast resistor. Assuming normal tractor wiring, power for the light circuit should come from the battery, not the ignition circuit.

Joe

Soundguy

Three wires exist on that junction to be exact:
1) wire from the alternator that reads "TO BAT"
2) wire supplying current to the ign switch
3) wire to the positive battery cable for charging

This is NOT the place to grab a 'hot' for accesories then?