The ignition switch sends voltage through all of the components that start the engine. An ignition switch is found inside the steering column of a vehicle and is connected to the lock cylinder. When the key is turned to the on position, voltage flows from the battery to the starter and distributor.
The ignition switch also provides power to all of the engine's accessories and the engine control unit. It essentially routes power from the battery of the vehicle and to every other electrical component. A basic ignition switch has four functions. "OFF" turns the car off, "ACC" provides power to the accessory components, "RUN" turns the engine on and "START" is used only to ignite the engine. When the switch fails, the vehicle will not start.