The ignition switch is the device, controlled by the ignition lock cylinder, which completes circuits to activate certain systems in the car. Which systems are activated depends on the key's position. Typically, vehicles have four positions: ACC (for accessories), Off, On, and Start. The ACC position activates some basic functions such as radio, power windows and the blower motor. Off disables all functions except for lights and power locks, although on some vehicles the accessories may continue to function until a door is opened. The On position is for standard operation for the vehicle, allowing all electronic components to function and the ignition system to keep the engine running. When the switch is in the Start position, all of the above typically happens and the starter solenoid is engaged as well, cranking the engine and allowing it to start.
Ignition switches can fail over time, or if a wire becomes loose or gets broken. When this happens your vehicle will have a hard time starting, or not start at all, as the electrical circuit cannot be completed.
Most of today's vehicles have complex security systems in place, especially around the ignition switch, to prevent theft. For this reason replacing one is probably best left to a dealer or ASE Certified Technician.
We stock and sell a wide variety of quality ignition switches from these manufacturers: