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How to Wire a Relay for Off-Road LED Lights

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

relay wiring diagram explained

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.

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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

X2 52 inch dual row combo beam light bar

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.

atp wire harness

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:

40 amp relay

 

  • 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).

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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.

Check out our Wiring Accessories for harness extensions, rocker switches, and more.

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

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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.

Comments
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2/27/2023 3:14 PM
@Guest, There are several troubleshooting steps you might need to do to identify the root cause of the issue. We suggest checking if the relay first if is working or if it needs replacement.
10/14/2022 3:03 PM
Just replaced my halogen headlight globes with led ones. But my led light bar that is wired in with the high beams now wont work. Yhe wiring connections are ok. Do I need to change the light bar switch relay due to the low power draw of the leds.
6/26/2022 9:46 AM
This is the best and easiest diagram I have ran into, very self explained and nice to accomplish. Thank you.
6/3/2022 11:08 PM
I hooked my 22" led bar up running one wire through a toggle switch to the positive terminal on the battery and the other wire to the negative terminal it worked fine now it won't come on does it have a built in fuse
4/19/2021 11:09 AM
How come the wiring diagram doesn’t show where the fuse should be?
3/30/2021 6:12 PM
How about connecting that harness to a switch pod like a MLC
3/4/2021 7:37 PM
wired a set of fog lights on my utv using the harness that came with the kit.  After getting everything wired up the button/rocker switch red light stay on after turning off the lights and after turning off the utv and removing the key.  Basically the switch is drawing power even when everything is off.  What can I do so that the switch light will go out and not cause a draw on the battery?
2/8/2021 10:10 PM
Does there need to be a joined wire off of 30 that is connected to both the positive side of the battery and the switch?
12/30/2020 12:33 PM
@Tanya

There is a fuse attached to our wiring harness that he can switch out. If you are still having issues with it please send us an email and we will investigate further.

- Ciara
Extreme LED
12/29/2020 3:48 PM
Tanya


My husband got a light bar for Christmas and when he first got it he hooked it up to the battery and later that night the light bar wouldn't turn on so I am trying to figure how he could hook it up to a fuse so if it blows out the fuse he could change just the fuse.
12/29/2020 3:47 PM
My husband got a light bar for Christmas and when he first got it he hooked it up to the battery and later that night the light bar wouldn't turn on so I am trying to figure how he could hook it up to a fuse so if it blows out the fuse he could change just the fuse.
11/29/2020 4:40 AM
Do I also need a resistor with the the relay wire harness for fog led lights?
11/28/2020 10:23 PM
I have a 2020 Polaris Ranger 1000 xp North Star Pre.
I installed a small light bar in the front and two small lights on the back. I used the pulse bar under the hood for the front one and the pulse bar under the head liner.
When i went to drive the winch won’t work unless I turned on the light bar in the front and all so the lights on the back came on. Also without the light bar switch on I didn’t have power to the windshield wiper. What did I do wrong.
11/9/2020 7:42 PM
i have a 4 gang switch box,40a fused. can i use 1 relay to wire up all 4 switches.
the box has its own power and ground that control it all. please email me back at kylepollock03@gmail.com thanks
10/26/2020 12:47 PM
How can I wire it with it to only work with key on......as wired I can flip the switch and it comes on without key in ignition.
10/18/2020 5:52 PM
Am needing some help on the relay switch think it might be wired wrong. The switch light comes on when flipped but my light bar does not. Any help would be greatly appreciated?
7/12/2020 12:43 PM
Thank you this helped me out and understand how to wire my lights
7/11/2020 10:33 AM
Hi, I have a 2020 ram 1500. The fusebox under the hood has terminal post. Can I run the poet for the relay to one of the post?
Thanks mingya
6/5/2020 5:36 PM
how do i wire two 20inch lightbars,do i need two relays,or two wiring harnesses?
5/30/2020 4:54 PM
i have a LED light bar and my switch has 4 wires. 2 red and white
1 green and 1 black my relay has 5 connection. 30, 85, 86,87 and 87a. how do i wired the lights
4/17/2020 12:15 AM
I am using a 20amp toggle switch and a 20 amp arc fuse. Do I still need a relay.
4/13/2020 5:32 AM
With a 5 pin relay can you run 2 sets of leds on 1 switch and have either or setup? This is so I can switch back and forth what lights are on..Thanks..
3/20/2020 1:34 PM
I have a small light bar which has a blue red and black wire which wire does what
2/23/2020 11:03 AM
Hi im wondering if I can run 4 3 1/2inch led lights on my truck with one relay and two switches is that even possible they are small so I don't think they will pull to much power to blow a fuse but I have no clue yet. I already have two on the back but want to throw two on the front as well. So can I just bridge the 87 to those lights and bridge my switch ??
2/16/2020 9:25 AM
My question just learning and getting to know what wire gauge and switch relays. My question was I bought an led wiring harness that’s only good for one light, it was on clearance and wanted to get a hands on feel of what I’m dealing with, I have 6 led rock lights, so do I need a harness for each one of the led lights or I’m guessing there should be larger harnesses without having to have in my dash 6 switches to turn on. Lol
2/10/2020 8:02 AM
I hooked up your Alpena ezlink light LED bar and the lights won't come on the switch is lit up in the relay switch cup right but it won't come on would it be possible that the ground is not grounded good
11/26/2019 8:11 PM
I have the 38” Extreme LED x6s. I don’t want to run two switches on the light bar. Would I be able to connect both positive wire and run it through a single relay?
11/15/2019 10:47 AM
I installed a 72 watt led light bar on my ingersoll tractor works fine just off tractor battery soon I hook power cable to battery I blow the light bar fuse I’m using a wire harness and relay cane in kit
10/26/2019 11:06 AM
So if I'm understanding this correctly, to run my light bar and drive lights (came as a three light set), I need to still run power from the battery to the 30 switch and then cut the power to the switch and draw that power from my high beam power to feed the 85/86 side of the relay?  I do want the lights on a switch so they can remain off, but when on I want them to shut off with the high beam.
8/27/2019 7:49 PM
Hi, I am confused, you stated that cutting the wire to the # 30 terminal and splicing into a high beam circuit would allow control by the high beam circuit.  I see two wires going to #30 terminal on the relay.  A red one and a white one.  Which one should be cut.  Thanks,  Bill
5/24/2019 5:22 PM
What if I have an auxiliary fuse block hooked up to the battery and a 120v relay hooked to the fuse block. Do I still need to relay each individual light?
4/18/2019 8:38 PM
Can I wire a light bar to come on with my cargo light and when needed a separate switch in the bed when the cargo lamp is off.
3/23/2019 8:48 AM
Will a vf4- 15f13 relay workin a 22 inch light bar
1/27/2019 12:50 AM
I have a 2016 polaris slingshot and i have LEDs all over but right now I install a fuse block that has a constant power and I have light bar on the front can you tell me how I can install a on and off switch where I can turn my LEDs off and keep my head light rear light on thks RONNIE
1/6/2019 7:12 AM
Im installing a auxbeam 52 inch light bar and it came with a wiring harness after hook up a red light stays on all the time you turn it on and green light comes on but the red light stays on .how do i bypass the red light so its not on all the time. thanks
1/5/2019 8:42 PM
How do you wire a 6 prong toggle switch for a led light bar
1/3/2019 6:08 AM
I’ve installed two 4” LED light bars to my 2018 Polaris 4-wheeler.
My relay switch has 1 wire on each side with the fuse inserted (20amp. Is this correct?)
Please give me step-step instructions on how to wire the two LED lights to this relay, what amp should I use, and how to wire it so I use a toggle switch. I want these LED bars to turn on and off with the toggle switch.
12/29/2018 1:33 PM
Can I just use an accessory from fuse box instead of having to splice into headlights?
12/24/2018 11:40 PM
How would I wire the relay to have control through a switch and or w hi or low beam from a vehicle. So I could trigger w hi beam or also the switch in the dash? So it could be triggered via hi beam and independently by the dash switch
11/26/2018 1:59 AM
Hi, I just installed a third 'spot' driving light. I added another relay to separately power the light so as not to overload the existing relay (30 AMP).
However things are not quite working as they should. The new spot comes on with the low beams and turns off when I hit the high beams.
I have checked and the relay 'power' is spliced into the high beam wirs so that should only suppy power to the relay when i hit high beams.
Any thoughts folks? Could my relay be dodgy?
Paul
10/18/2018 6:59 PM
I have a light bar mounted to a Polaris Ranger wired through a relay.  The light works fine with the switch on but slightly glows with the switch off.  Any idea how to fix this?
9/11/2018 7:43 PM
I wired a set of fog lights on my utv using the harness that came with the kit.  After getting everything wired up the button/rocker switch red light stay on after turning off the lights and after turning off the utv and removing the key.  Basically the switch is drawing power even when everything is off.  What can I do so that the switch light will go out and not cause a draw on the battery?
8/25/2018 4:28 PM
Looking at wiring a light bar to the high beams and to the outfitter switch on a 2018 f350 to do what your talking about.... could u draw me up a diagram to do this?
5/10/2018 3:03 AM
Hello, hooked up a led light bar on my grill,now I lost all electrical power.what could of happened?
                  Thank you
3/16/2018 2:25 AM
I have just wired in 2 hid spotlights. I only have a 3 prong switch to turn on and off. How shall I wire in high beams with this.
2/5/2018 5:46 PM
I have a 22 inch curved lightbar with a on and off switch in the cab, I want to put two 4 inch pods on my truck as well, what type of wiring harness do I need to tie into the other one? I can't imagine having to have 3 on off switches... thanks
1/30/2018 12:06 AM
Hello,
I got a 50 in curved led light bar for my Jeep came with two pod led lights... do i need to buy extra black and red wire to hook up the pods? I’m having difficulty on to how those should be hooked up.
10/11/2017 9:23 PM
Thanks mate, helped me no end, identified faulty relay. light bar working again. I live in the Australian bush and we work on the principle when driving at night, "the more light the better""."
3/23/2017 7:57 AM
I wired my 50" led light bar up with the wiring harness supplied with and the switch also, but the red light on the switch stays on when off position it lights up green when on . My question is should the red light ALWAYS be on even with key in off position? Thanks
2/15/2017 8:45 AM
I have a light bar that came with a wiring harness and switch. I want to remove the factory switch as i am running multiple light bars and use a third party switch panel with 6 rocker switches run in a series.  On the back of the rocker switch, there are 5 blades.  Two ground, two hot and a 5th blade that goes to the Relay or LED.  These are 20 amp switches.  My question is, the switch panel needs to be run to positive (accessory or ignition) and the remaining open blade will run to the wiring harness.  But in the wiring harness that originally came with it, there are three wires going to the factory switch..Red, black and yellow that lead back to the relay.  I am assuming the remaining open blade will correspond to the yellow wire in the wiring harness.  But, what I am to do with the red and black wires in the wiring harness?
10/11/2016 8:46 AM
I have followed this helpful instruction here to a "T"..
But only half of each aux rear lights light up.. each light has 6 LED's but only 3 on each are lighting up..
can anyone advise..
8/23/2016 5:21 PM
@frank, no you wouldn't want to do that as the LED light would then try to draw all the power to run it from the same wires/circuit that is powering your high beam lights. That circuit isn't meant for that additional load and would likely blow your fuse.

Instead, you'd need to splice a wire from your high beam wire to the 30 prong on the relay. Then if either the high beams come on OR you flip the switch, either one of those will close the relay and turn on the LED light.

Hope that helps!  
8/23/2016 4:23 PM
I have a relay kit with a switch already, I want my led bar to turn on with the high light switch. Can I just connect the wires that go to the battery to where the high light, and keep custom switch on at all time?
4/18/2016 5:48 PM
can I run my 35 inch led light bar of my 2015 gmc sierra driving light switch if I use a relay? thanks
2/5/2016 6:16 AM
@nathan:

Yes, you can do this; basically, you would put your switch in between the reverse wire and 85, so that the relay would only trigger when the switch was on (to make the connection to 85).

You could even do this: Get an SPDT switch, with center off, and wire the common terminal (center, usually - but check it first) to the relay (85). Now, wire one of the remaining switch terminals to your power source, and the other to your reverse wire.

Now, when you set the switch to the middle (off) position, your reverse lights operate as normal (and don't trigger your extra lighting). When you flip the switch one way, your reverse lights will operate the relay (and your light setup). When you flip the switch the other way, your lights will turn on independent of the reverse lights.

This is a simple modification that might be worth doing depending on your needs, because after all - who wants to redo their wiring if they don't have to, right?
1/24/2016 3:07 PM
could I connect the reverse wire to 85 as well as to an on off switch so my lights come on during reverse and while parked just flip a switch and lights will come on that way as well.