Automotive relays are magical devices that make wiring different items into your vehicle a reality. If you’re tackling a big wiring job by yourself for the first time, relays might seem intimidating to use, but there’s no need to be scared of the little black boxes. In this video, Jeremy Stoermer from Holley shows you how automotive relays work and how to wire them.

A relay is designed to work as part of your wiring to make sure certain accessories can be used without overloading any circuits. Relays are also used to activate different accessories or other items depending on how they’re wired up. The relay is activated through a switch that can be turned on, or by some form of power being introduced to it.

Relays in the automotive world have either four or five terminals and which one you use will depend on your application. The relays are classified as a type A or type B layout and you need to match the relay you use to your application. The relay terminals each have their own designated job and need to have a specific item wired to it. Typically, you’ll be wiring in the battery positive, a ground, the trigger or switched power, and the powered accessory you want to activate.

Stoermer does an outstanding job in this video providing great details and explaining how a relay works. He shows you how to wire up four and five terminal relays, plus you learn about several other types of relays that you can use in specific situations.