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The typical car is equipped with hundreds of different electrical relays,whose job is to act as a kind of referee between circuits that need variable power to operate.Without relays,a large variety of electrical components on your car would fail to operate.



What Is a Relay?

  • Auto relays are fitted in between circuits with different amperage ratings, so that output or input from each circuit is regulated and they can safely "talk" to each other. In addition, an auto relay is used to operate multiple components when only one command is issued,so that a complex electrical gadget becomes fully functional with no delay.

How Does a Relay Work?

  • While operation may be simple, relays nevertheless rely on many crucial parts to control power safely and effectively. Typically, a relay will be configured in one of two different ways - single poll,single throw, double throw - and power is distributed through contacts which are either in the open or closed position. Power is generated through a coil, creating a magnetic field and activating the switch. In addition, relays must be equipped with regulators to avoid voltage spikes during normal operation that could damage sensitive components. Resistors or diodes are used to "snub" voltage spikes when they are placed across the coil and power is switched off.

How Is a Relay Made?

  • At the center of a relay is an electromagnet, made from a coil of finely-enameled copper wire, which is in turn wrapped around an iron core. At one end are switches and above the coil is an armature which will meet the switches in an on or off position. When current is applied to the electromagnetic coil, it attracts the armature and pulls it down against a spring that is attached to the top of the housing. When the energy supply is removed, the magnet is released and the spring returns the armature to the off position.

Why Do Relays Fail?

  • The rating of the relay may have been exceeded.
  • The relay may reach the end of its natural life after a specified number of operations.
  • The relay may encounter "hot switching" when it is subjected to excessive current in unexpected load conditions.

What Are the Symptoms of Failure?

  • Electrical components serviced by the relay will fail to work.
  • A circuit could overheat and burnout.

What Are the Consequences of Failure?

  • In the worst-case scenario, a relay failure could result in an electrical fire.

A relay may be one of the simpler components within an electrical circuit,but it nevertheless has a huge job to perform as it uses a comparatively small current in part of the circuit to control a sizeable current and voltage in another part.

If you have questions or concerns about relays 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.