Electrical Basics
How to seamlessly convert your car to a modern coil set-up
How to remove ballast ignition.
Ballast ignition causes much confusion, though it’s really quite simple. It’s an age-old method of getting the best possible spark at the plugs when starting the engine. On a 12V car with a ballast system, the ignition coil is rated at 6V or 9V. With the engine running, the supply to the coil passes through a ‘ballast resistor’. This drops the voltage to a safe level for the coil.
When starting the engine, however, the battery voltage drops to 9V or 10V due to the effort of turning the engine on the starter motor. A second power feed to the coil supplying full battery voltage is switched on and off by a pair of contacts, often on the starter solenoid. The contacts close when the starter is operating, thus feeding the coil full battery voltage and giving it a bit of extra power.
The contacts open again as soon as the starter is released, so the coil reverts to taking its power via the ballast resistor. This brief overloading doesn’t harm the coil, but does boost the spark.
Why, then, would you want to convert from ballast to non-ballast ignition? Perhaps a starter motor, ballast resistor or coil can’t be sourced as a spare part. Or perhaps the system’s been tampered with, mutilated or misunderstood by a hapless previous owner?
It’s sometimes easier to do away with a ballast system when adding electronic ignition, too. It avoids complicated wiring and allows the use of an off-the-shelf high-power coil that would otherwise overload the ballast resistor. Electronic ignition gives a strong spark under difficult conditions anyway, so the ballast system is surplus to requirements.