66-67 Dodge Charger Source Guide

Ballast Resistor


B Lockwood:Can anyone tell me what is the function of the ballast resistor that is on the firewall?


Don Dodson: It limits the current going to the coil in two ways. First when you reach down there and turn the ignition switch to crank the car, the ballast resistor is not in the coil circuit and the coil gets the full 12 volts to give the spark plugs a hotter spark for starting the car. After you release the ignition switch to the run position, the run position cuts in the ballast resistor and limits the voltage going to the coil. If the car starts OK but shuts off after you release the ignition switch, then the ballast resistor is shot. Lots of people carry an extra ballast resistor in their glove box. I have never had a ballast resistor go bad, but I guess some folks have. I don't carry a spare myself.
Electronic ignition systems usually don't use the ballast resistor since there are no points to contend with.