A common question we get is, "What is the relay for and how do I wire it to my light bar?" To provide more color to this, we will cover:
- What is a relay
- Why you likely need a relay
- How to connect your relay
What is a Relay?
A relay is an electrical switch that controls the power to your led light bar. It allows a low current "switch" circuit to control the electricity flow of the high-current circuit load, like your LED Light bar for example.
Why do I need a Relay?
When you create a circuit, a loop of electricity from the battery positive to your LED Light bar to your battery negative, if you just put a switch between the battery and the light, the switch has to be rated for the full current (amp draw) of the light. Our lowest amp draw LED light pods draws about 1.4 amps. While many switches will be able to handle that, for example, the Extreme LED Rocker Switches are rated for 20 amps at 12v. There are very few switches that are designed to handle the the draw of one of our larger light bars like the Extreme LED X2 52" dual row lightbar, which draws about 40 amps. If you are running too many amps through a component not rated to handle it, bad things can happen like overheating/melting the switch, melting the wires, or at a minimum reducing the current that is getting to your lights which will reduce the power output.
Another reason you may want to add a relay is to utilize electrical currents from existing "switches" in your vehicle. Let's say you want to have your LED Light Bar come on with your high beams, or reverse lights, for example. Read more about that below.
To see additional light bar options, checkout our full line of lightbars
How to wire your LED Light Bar using a Relay
The relay will have 4 prongs on it, marked 30, 87, 85, and 86. Kind of cryptic isn't it? Well if you are just going to use our wiring harness, and a switch, you don't need to know what any of this is, because it comes pre-wired and plugged in together. In fact, our lights also have plug and play connectors so the only electrical wiring you need to do will be connecting the harness to your battery.
However, if you are looking to use an electrical current from another "switch" in your vehicle such as your brakes, reverse lights or turn signals to activate your LED lightbar, then you'll need to do a bit of rework. We will refer to these existing functions in your vehicle as a switch, to clarify that these on/off functions that already exist in your vehicle can be used the same as a switch.
First, an explanation of what the 30, 85, 86, and 87 numbers are in the picture:
- 30 and 87 create the switch to your LED lights. By default this switch is open, so current cannot get from the battery to your lights.
- 30 is your power source for your LED lightbar. It connects to the positive (+) side of your battery or to a switched power source that only gets power when your ignition is on.
- 87 goes to the positive side of your LED lights.
- 85 and 86 use electrical current to create a magnetic force, which then closes the 30 to 87 switch and allows the electricity to flow to your lights. Without this current, no magnetic force is created, so the 30 to 87 switch stays open, and your lights stay off.
- 85 connects to the power source that you want to control the switch. For example, you could splice a wire off your high beam switch wire or off your backup light wire
- 86 connects to a ground.
(Note: 85 and 86 can be reversed, but our harnesses have them setup this way).
What if I don't always want my LED light to come on with my high beams or backup lights?
Good question! So you'd want another switch on your dash that you turn off and on. When it is off, and you put your high beams on, your LED light will still be off and vice versa. In this case, you need to wire the dash switch in between the trigger current, i.e. the line you spliced off your high beam wire or your backup light wire
With our wiring harness, all you need to do is cut the wire coming from the switch to the 30 prong on the relay and wire it to your high beam lead or your backup light wire. That way, when you do have your high beams on, the current from that goes to the dash switch first, and if that is off, the electricity can't get to the 85/86 circuit to create the magnetic force to close the 30/87 circuit, which turns on your LED lights.
Still have questions?
Check out our blog post about How to Know Which Off-road LED Light Bar Wiring Harness You Need
or our Wiring Harness Diagrams. If you're still stuck, we are here to help, send us an email or give us a call
Meet the Author: Extreme LED has been helping offroad enthusiasts with their LED lighting needs since 2011. We have built our company to provide you with the best experience from shopping to customer support and ultimately use and longevity of our products. Our high-performance LED Light Bars & Pods are covered by our Lifetime Warranty and with free shipping over $100, you can rest assured that you are getting a high-quality product that will provide long-lasting lighting for your vehicle.