The ballast resistor Is an electrical resistor that is diverted into and out of the supply voltage to the ignition coil system. This ballast resistor actually lowers voltage after the engine is started to reduce or minimize wear on ignition components. It also helps the engine to fire much easier by effectively doubling the voltage provided to the ignition coil when the engine is being cranked. Not all car manufacturers used a ballast resistor in their ignition systems.
The ballast resistor is a resistance wire which is inserted in series in the primary circuit between the ignition switch and the positive terminal of the ignition coil.
The heat sensitive type is wound onto a heat resistant former and placed in an open ceramic holder with connecting terminals at each end.
It is normally located close to the ignition coil in an exposed position, so that it can transfer its heat easily to the air.
The purpose of the ballast resistor is to drop the nominal battery voltage down to approximately half its value for ignition coil operation.
A ballast resistor primarily refers to an engine component that lowers the voltage after starting the engine, since the voltage required by the engine drops significantly after starting. It is an electrical resistor that affects the voltage supplied to the ignition coil.
The ballast resistor makes the engine much easier to start by also doubling the voltage provided to the ignition coil when the engine is being cranked. Not all automobile engines have ballast resistors.
Source: CDX Global & Wikipedia - en.wikipedia.org
