Greetings . . .

I believe the resistor is placed in the circuit for point life. 12 volts is hard on contact points due to excessive arc which leads to erosion. I think the resistor steps the voltage down to 9 or 8.

You should check the specs on the coil you've fitted - I think most have the ballast resistor built in. If so there is nothing to do.

regards,
Keith

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