Car’s ignition switch provides several purposes. The very first thing is, it allows you to control the power to many of the car’s accessories, which prevents from running down the car’s battery when your car is parked for long period. It also serves the greater purpose of connecting the starter to the battery, allowing the battery to send powerful surge of electricity to starter when the car is being started.
The term ignition switch is used to refer to two very different parts, i.e. the lock cylinder in which key is inserted and the electronic switch which is just behind lock cylinder. There are some cars in which both these parts are combined into one unit and in other cars it remains separate. It’s better if you check your car shop manual before buying any ignition switch to ensure that you are buying the correct part.
To start a car, the engine should be turning. In the days before, ignition switch and engines had be turned with the help of a crank on the front of the car in order to start them. Starter, in the car performs this operation by turning engine’s flywheel, which is large and flat disc with the teeth on the outer edge. Starter has gear which engages these teeth when it is powered, briefly and rapidly turning the flywheel and then the engine.
Ignition switch has four positions in it, i.e. off, accessories, on and start. In some cars there are two off positions, i.e. off and lock, the one which turns off the car and the other allows the key to be removed from the ignition. When in accessories position, the accessories like radio, is powered; whereas the accessory which use too much of battery like window motors remain off to prevent the car’s battery from being drained. When engine is not running, accessories use least amount of battery power, which is why drive-in movie theaters recommend that the car should be left in the accessories mode during the movie.
When the car is in on position, it turns on all the car systems, including fuel pump, it is in the position where ignition switch remains in and car’s engine is running.