My car has no points...why is there a ballast resistor?

Question:

In the February issue you state that the ballast resistor is used to limit the current to the contact points. My 1978 MGB has a ballast resistor and a factory pointless distributor. Why is it on the car from the factory if there are no points to protect?

Answer:

Your MGB has a ballast resistor to £* limit the current to the coil. The car uses a 6-volt coil connected through a ballast resistor, so the car’s 12-volt battery is stepped down to 6 volts when the engine is running. The starter motor on your MG has an extra terminal that provides 12 volts for a hotter spark only when the starter is cranking the engine to start it. This is connected to the coil, and bypasses the resistor so your 6-volt coil gets 12 volts for a hotter spark during startup. But as soon as the engine is running the system reverts to 6 volts.

Your MGB wouldn't have a conventional ceramic ballast resistor, though. Instead it bas a special resistor wire built into the wire loom. It usually is a green and-white wire that is connected to a pink-and-white length of wire that acts as a resistor. Many MG owners change this out to a conventional ceramic ballast resistor to prevent the original wire-type resistor from overheating and damaging the rest of the wiring. Ballast resistor fires are not unheard of on MGBs.