Newbie ques: What are Ballast Resistor and Voltage Regulator for?

Strocker's right


Some newer electronic ignitions don't use a ballast, but in "the old days," it was twofold

The system draws different current at idle than at high RPM, and the ballast was supposedd to mitigate that change somewhat, but when 12V cars came along it provided a SECOND function.

All 12V cars used a "resistor bypass" circuit. In the case of Ford/ GM it was an extra contact on the starter solenoid. On Chrysler stuff, it's the "ign1" circuit from the ignition switch.

This bypass circuit fed "hot" battery voltage to the coil during start, so that you still had a good spark during engine crank. When you let off the key, the ballast was back in the circuit.

Stroker's also right about the voltage regulator. If you take an alternator and bypass the regulator, and start the car, it may not charge much or at all when at idle. But as you increase engine RPM, the alternator voltage will just keep going up and up and up, until the battery is LITERALLY boiling. If the battery gets charged up, you can keep going up with voltage until lamps burn out.

Believe me, car manufacturers don't just throw parts on a car for fun.