How to Wire a Relay

In this wire a relay guide, we’ll offer a broad overview of how to wire a relay after talking a little more about what a relay is and the applications where one can be useful. If you’re replacing a relay in a vehicle, machine, or appliance, we can help you get the products required to complete the job. Read below to learn more with Gateway Cable Company. 

What is a Relay? 

When you flip a light switch in your home, the physical act of flipping the switch turns the light on. A relay is an electrically operated switch, meaning there is no human action required to operate it. You will often find relays in automobiles, machines, and appliances. 

What Applications Are Relays Used For? 

As we mentioned before, a relay is a switch that is controlled by electrical power, i.e. a control module or another switch. In applications like machinery and automobiles, a relay can be utilized to automate the power source, so that electrical circuits can be switched on and off at particular times. Automation is one reason why relays are useful in such applications, but another benefit to consider is that a relay allows for multiple circuits, of varying voltages, to be switched within the same relay simultaneously.

Using a Wire Relay Diagram

In order to learn how to wire a relay, you really just need to know how to read a wire relay diagram. On the side of the relay switch, you should see a numbered diagram. The numbers correspond to the contact pins and coil pins and will instruct you on how to wire the relay you’re working on. Once you understand which numbers correlate to the contact pins and coil pins, you can move forward to wire the relay.

Let’s use a standard 12V relay switch for automotive applications as an example, which would have two coil pins and three contact pins. As you work, remember: 

  • The coil pins transfer current through the coil. One numbered coil pin grounds the relay, while the other numbered coil pin is connected to the switchable power supply. 
  • Two of the contact pins will be used as the connection to the accessory you want to operate with the relay. 
  • The final contact pin is connected to the battery power. 

You must adhere to the wire relay diagram in order to connect all of the pins in the correct order! 

Learn More with Gateway Cable Company

If you don’t yet have everything you need to replace a relay switch in a machine or vehicle you’re working on, explore our product catalog online or request a quote from us to get the products you need. If you have any questions about what products are right for your job, you can contact us and we’ll be glad to offer more insight.