This is how the resistance affects current.
Current is what you are trying to keep low enough to save the points and the coil.
Volts = Resistance X current. This is Ohms law.
So just change it to represent Current instead of Volts, and you get...Volts (divided by) resistance = Current Just some math to make you nuts..:) Now on to the part that matters.
1, 6 volts (divided by) 1.2 ohms (the smallest resistor in the list from (tcleaderman thank you Sir)=5 amps.
Still with me?
2, 6 volts (divided by) 1.8 ohms (the biggest listed) = 3.33 Amps.
All other values will be in this range.
This is the current that goes to the coil and the points. And is what you would get if the coil was those resistance values. Any way it is a "limit" for the points. Because that was what they were designed for. So when we change to 12 Volts we need to get the current down to these "limits" to prevent overheating the coil and the points. So to guess, and it is a guess, that the coil is 2 Ohms, to 1.5 Ohms. Let us try to get the current in the same range with 12 Volts.
1. 12 Volts (divided by) 1.2 Ohms (resistor) + 1.5 Ohms (coil)= Current. 12 Volts (divided by) 2.7 Ohms ( just added the resistor to the coil)= 4.44 Amps
Yes I cheated a bit but that is OK. The worst real world is the smallest resistor and the smallest coil.
2. 12 Volts (divided by) 2 Ohms + 1.8 Ohms = Current. As before, 12 Volts (divided by) 3.8 Ohms (again I just added the points and the coil) = 3.6 Amps. So the worst case is 4.44 Amps and the best case is 3.6 and the "limit" is...5 Amps to 3.33 Amps and surprise...we are within those "limits" The values are just not that critical. After all we just want the Truck to run for a long time. Hiperformance guys have different goals in mind. I hope this is helpful.
