How to Wire a Relay: The Less Complicated Way

Because your car has a huge responsibility in taking you to places, you also have the responsibility to make sure you take care of your car as well. This means the daily tuneups and maintenance, as well as the driver's etiquette to keep you and your car safe while driving.

One of the things you'll need to learn to do is how to wire a relay. This is a very important part of your car, especially when using a ton of power.

Not sure how to wire a relay? Read on as we show you everything you need to know about the relay and what you need to do for wiring it for optimal performance.


What is a Relay?

Your car uses a lot of power while it's running. The engine alone will need a certain amount of electric currents for it to start. Apart from that, you have your other accessories that help protect and improve your drive: The headlights, your radio, or other features your car may have that requires more power than it can handle.

So where does the added power come from? That's where your relay plays an important role. A relay is a switch operated electrically, activating an electromagnet to create a break or circuit. Basically, it helps convert lower current circuit into a higher power that allows your vehicle to run smoothly.

There are two types of relays: The switch and an amplifier. Switch the small lever on, and you'll be able to use features in your car that require higher electric current. But with an amplifier, also used for vehicles, it automatically converse small currents into larger ones.

Importance of a Relay

Your relay has a lot of benefits you'll be able to take advantage of. It isn't only something that helps bring life to your car's automatic features.

  • A relay will also be able to switch off applications quickly ensuring that you are free of safety hazards such as overheating or fire.
  • Installing a relay for your lights is important to keep them shining bright. While you can make do without a relay when using a lower voltage, using both a relay and fuse will help maintain the brightness of lights that use more than 30W of power. They also work great when adding horns for your truck or better speakers.
  • Relays are automatic switches, so these handy devices will be able to detect how much power to use. It can activate multiple circuits from just one output, making performance more efficient.
  • Relays can help carry out logic functions, which is great for those who have after-market projects or applications for their vehicle.

What You Need to Wire a Relay

You will need to prepare a few things when wiring your relays, such as:

  • Safety gloves are needed as well to assure no accidents or injury.
  • The main thing you will need when wiring your relay would be the relay itself. There are two types of relays: The 12v or 5v signal. 12v is the standard for automotive batteries, while 5v is used for sensors.
  • You will also need to make sure you have the ground and accessories you'll be hooking the relay to, which may be horns, lights, or your car battery.
  • A fuse is also needed, since you have to fuse your power wires to properly connect them.

How to Wire a Relay

1. Understand the Basics

What you should know about relays is that they come in different numbers and four wires, used to help determine what and where you will hook these wires to.

  • 30 is a constant positive power for your car battery. It's an input terminal.
  • 85 is coil ground, wired to negative battery terminal or grounded metal panels in your car.
  • 86 is coil power for your control source, used as a switch or circuit.
  • 87 is the positive power output and connected to -30 pin when it is powered. It's an output terminal.
  • 87a is connected to -30 pin when the coil isn't powered. It may or may not be part of the usual relay.

2. Connecting

When wiring the relay to any of your car accessories (lights, car battery, or horns), you can follow these connections:

30 and 87 create a switch for your headlights, while 85 and 86 create a magnetic force, allowing the electricity to flow to your lights. You will need to connect 85 to a power source that will control your switch, while 86 is connected to the ground.

When connecting it to your car's ignition, simply connect pin 86 to your car's IGN or ACC circuit. When connecting a new horn, hook the horn wires to the pin 30 and 87, with pin 85 being the common ground.

3. Test

Once you've got everything connected to the right places, then connect the relay and the accessories to your vehicle. Test it out to make sure everything is running smoothly.

Take note that relays will need replacement over time. Usually, it takes 100,000 operations until you have to replace your relay. And there you have it! As long as you connect the wires to the proper pins, wiring a relay is easy and will only take a bit of time.

In Conclusion

When it comes to caring for your car, you will need to learn how to wire a relay. This will enable your car to work properly, ensuring that power is distributed evenly and without chances of overheating.

Hopefully, this article on how to wire a relay helps you become more knowledgeable with the importance of your relay and how you can wire it to improve on its performance. So what are you waiting for? If you need to wire your car's relay, then follow these steps!

We hope you enjoyed the article. If you have any more questions or tips on how to wire a relay, then comment down below. We'd love to hear what you have to think.

Tom Nguyen

I’m Tom, and I’m avid fan of automobiles! I love cars and learning more about how to tweak and repair them to make them look and perform better. Through a lot of projects and research, I make it a point to share my knowledge to other car enthusiasts like me.