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What Is a Switch?

An automotive switch is a simple electromechanical device that is fitted within an electrical circuit and controls whether the circuit is “on” or “off.”

How Does the Switch Work?

In a typical car, there are hundreds of switches set up in different configurations, based on how many separate circuits are controlled by the switch and how many positions are required. For example, a “single poll/double throw” switch means the switch is controlling one circuit and there are two positions available, usually on or off. Some switches are particularly complicated, such as the one that controls the vehicle’s ignition. This can be configured in several different ways allowing power to the accessory circuit, allowing power and enabling the circuit (to run the fuel pump, coil etc), or to allow power to the starter, which then triggers the engine.

Switches can be very simple “on/off” devices or they can be linked to more complicated, electromechanical devices called relays. These latter devices are always featured when different voltages apply, as a relay can control the difference between these parts of the circuit.

Some switches are activated by the driver, while others are activated by components within more complex circuits.

How Is a Switch Made?

In its basic form, an auto switch is made from two conductive parts that when closed complete a full circuit and when open breaks this circuit. Materials are chosen to be strong, resistant to abrasion or corrosion, and relatively low cost. Where the switch is activated by the driver, the activating mechanism is protected by insulation to make sure that no electricity flows to the user.

Why Do Switches Fail?

  • An electrical spike in the circuit may cause the switch to burnout.
  • It may short out internally.
  • It passes its maximum number of recommended operations, but this is very rare.

What Are the Symptoms of Failure?

  • A component that fails to turn on or off and remains in position, regardless of activation.

What Are the Implications of Failure?

  • Where safety components are concerned, incorrect signals can be sent to other drivers (as in the case of the brake switch).
  • An interrupted circuit could create a parasitic drain on the battery.

Automotive switches are over-engineered for their purpose and should continue operation without any problem over the lifetime of the circuit it controls.

If you have questions or concerns about automotive switches or any of your vehicle’s components, come into your local Pep Boys where we can answer any question, help you find any part, or perform any vehicle service you might need.