Dual Ballast Resistor
Normal side of dual ballast resistor is a compensating resistance in ignition primary circuit. During low speed operation, current is maintained in this side of ballast resistor for a longer period of time, causing it to heat up, and resistance to increase. This action reduces voltage in ignition primary circuit, thus protecting coil (do not replace ballast resistor for this heated condition). As engine speed increases the amount of time current is maintained in this side of the resistor is shorted, causing it to cool off, and resistance to decrease. This action raises voltage in primary circuit which is required for high speed operation. The auxiliary side limits voltage to control unit thus protecting it.