The ballast "resistor" is a wire wound resistor design the reduce the voltage to the coil, as it gets hotter the resistance goes up and reduces the voltage to the positive side of the coil even more.
Mopar engineers design the wiring to the ballast resistor to have a 12 volt bypass on the starter circuit to provide 12 volts to the coil in the start position only, bypassing the ballast resistor to help the motor start quicker and better, hot or cold up scope

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)