An ignition switch, starter switch or start switch is a

switch In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...

in the control system of a

motor vehicle A motor vehicle, also known as motorized vehicle or automotive vehicle, is a self-propelled land vehicle, commonly wheeled, that does not operate on Track (rail transport), rails (such as trains or trams) and is used for the transportation of pe ...

that activates the main electrical systems for the vehicle, including "accessories" (radio, power windows, etc.). In vehicles powered by

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...

s, the switch provides power to the

starter solenoid A starter solenoid is an electromagnet which is actuated to engage the starter motor of an internal combustion engine. It is normally attached directly to the starter motor which it controls. Its primary function is as the actuating coil of a co ...

and the

ignition system An ignition system generates a spark or heats an electrode to a high temperature to ignite a fuel-air mixture in spark ignition internal combustion engines, oil-fired and gas-fired boilers, rocket engines, etc. The widest application for spark ig ...

components (including the

engine control unit An engine control unit (ECU), also commonly called an engine control module (ECM), is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance. It does this by re ...

and

ignition coil An ignition coil (also called a spark coil) is an induction coil in an automobile's ignition system that transforms the battery's voltage to the thousands of volts needed to create an electric spark in the spark plugs to ignite the fuel. So ...

), and is frequently combined with the starter switch which activates the

starter motor A starter (also self-starter, cranking motor, or starter motor) is a device used to rotate (crank) an internal-combustion engine so as to initiate the engine's operation under its own power. Starters can be electric motor, electric, pneumatic ...

. Historically, ignition switches were

key switch A key switch (sometimes called a keyswitch or lock switch) is a key-operated switch. Key switches are used in situations where access needs to be restricted to the switch's functions. Key switches are available as components with solder connecti ...

es that requires the proper

key Key or The Key may refer to: Common meanings * Key (cryptography), a piece of information that controls the operation of a cryptography algorithm * Key (lock), device used to control access to places or facilities restricted by a lock * Key (map ...

to be inserted in order for the switch functions to be unlocked. These mechanical switches remain common in modern vehicles, further combined with an

immobiliser An immobiliser or immobilizer is an electronic security device fitted to a motor vehicle that prevents the engine from being started unless the correct key (''transponder'' or ''smart key'') is present. This prevents the vehicle from being " ...

to only activate the switch functions when a

transponder In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend word, blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a T ...

signal in the key is detected. However, many new vehicles have been equipped with so-called "keyless" systems, which replace the key switch with a

push button A push-button (also spelled pushbutton) or simply button is a simple switch mechanism to control some aspect of a machine or a process. Buttons are typically made out of hard material, usually plastic or metal. The surface is usually flat or sh ...

that also requires a transponder signal. The ignition locking system may be sometimes bypassed by disconnecting the wiring to the switch and manipulating it directly; this is known as

hotwiring Hot-wiring is the process of bypassing a motor vehicle's ignition switch and thus starting it without the key. It is often utilized during a vehicle theft. However, a legitimate vehicle owner who has lost a vehicle key or starting a vehicle with ...

. Ignition switches are generally a simple repair that can be completed without much knowledge. They are mainly vehicle specific and plug and play.

See also