How To Wire An Automotive Relay Switch, With Diagram, 4 Pin

Quick and easy way to wire a relay to safely power added lights. Why you need a relay is also covered. This video will explain details of how to wire a relay switch for off road lights, compressors, or any other added accessory. We're using a four pin relay, couldn't be any simpler. A diagram showing a 4 pin relay makes it easy to understand.
How To Wire An Automotive Relay Switch, With Diagram, 4 Pin

[@SouthernTexasVaqueros]

By far the simplest explaining I’ve ever heard. Great info !! 👍🏼👍🏼👍🏼

[@WanderlostOverland]

Glad it was helpful!

[@TommyJensen-pl8qz]

if in a car, for example, you blink to the left and want to stop, the light goes off on the same side while the blinker is activated and also on the right side, which relay should you use?​@@WanderlostOverland

[@carolcarpenter7133]

Thank you. You explained it perfectly.

[@edryan562]

...you don't know(or maybe you do) how many how to relay sites until I tried yours. It's amazing how straight forward conversation really works. Thank you very much. Ed

[@WanderlostOverland]

Thank you so very much!!!

[@christoph404]

Greetings from Scotland, very straightforward and easy to follow! many thanks! that helped me with some work I'm doing on my old TR6 car, here we call those yellow connectors "Spade Connectors", I'm sure they might get called something else in other parts of the world.

[@glasshalffull2930]

They call them “spade connectors” here in the States too, but he forgot.

[@adamghahate3323]

Do I already know how to wire a relay? Yes. Am I going to watch this video anyway? Also yes.

[@j81851]

Sensible. Practical. Knowledgeable. Contrary to what most videos end up being this one is accurate and to the point. You are a very friendly and relatable presenter with great ACCURATE (sorry if I shout but as an electrical instructor I am so excited to find your channel) material worth viewing and using!! Please keep it up.

[@WanderlostOverland]

I appreciate that!

[@VanillaGorilla502]

Back again, you guy's really do have the best Overland build & 4Runner modification channel. Thank you the invaluable content.

[@WanderlostOverland]

Our pleasure!

[@MrBill2U]

Thank you for explaining this and making it very easy to understand.

[@WanderlostOverland]

You're very welcome!

[@JamallWilliamH]

Love this explanation. You saved me, wiring up air horns on my Yukon🎉

[@habakkuksam]

I have learn alot from your channel congratulations 👏

[@kabandajamir9844]

The world's best teacher

[@Bud4me0007]

Thanks for the video. You explain it so easily, that I have confidence to it myself.

[@WanderlostOverland]

Glad it was helpful!

[@kirkhustle3718]

It's so easy a Lowlander can do it, thx boss!!

[@WanderlostOverland]

No problem!

[@Singlemiked14]

2:33 - That is exactly what I needed to know. Thanks!

[@WanderlostOverland]

Glad we could help!

[@rwarts5150]

Great video Sir 👍 I know very little about automotive wiring but I thought I knew enough to extend the ground wire from the relay 6 inches using the same gage wire but after doing this seemingly simple thing the lights don't work yet the red and green lights on the switch work and fuse is still good so I have no clue what happened or how to fix it ?

[@childhospital7280]

simple and beautiful illustrations

[@WanderlostOverland]

Many thanks!

[@marianmarian504]

Very good explanation... My question is ... Can i remove the switch and have a direct power to the lights? How i can do this? Just remove the wire from 86?

[@MrRoostersmoke]

Thanks for the info!

[@WanderlostOverland]

Any time!

[@frankoneyjr.4515]

Great video !

[@WanderlostOverland]

Thanks!

[@antonioibarra6858]

Thanks for your video

[@WanderlostOverland]

Our pleasure!

[@VanillaGorilla502]

Wish I seen this two months ago when I wired my Rigid D2’s up. Couldn’t use the Air on Board switch because the original D2 Pro’s didn’t come with a relay.

[@woadscout9955]

Thank you for such a great explanation video! How do you know which number of fuse to use? 10,15,20,etc?

[@WanderlostOverland]

We always go by the amperage our accessory is stated to draw and go up to the next size fuse. If its 20amps we put in a 25amp fuse.

[@woadscout9955]

@@WanderlostOverland thank you so much, I’ve learned a ton from your videos and appreciate your responses!

[@andrewbennett6359]

So I could wire this sucker into my fuse box for my starter, with a killswitch in series along the control wire, yes ?

[@louwrensterblanche2860]

Hi. On toyota oem light switch 4 wire green red red and black witch wire go where on the relay. If black go to body and one red to tail fuse . Where sould green and reg go to light up switch corectly. Thanks for all your infi.

[@avelinovelez5090]

Thank you very much great video very informative 👍

[@WanderlostOverland]

Glad it was helpful!

[@eddlovekutsiwa9]

You are great, thanks a lot

[@Bobodeman]

Im wiring spotties up for my bike. Does the switch still get wired to fuse box? And what if the switch has a light?

[@thisthatwhatsup-mh3hq]

Is it possible to have an on and off switch manual hooked to my fan relay inside my engine fuse box? So I can turn it on manual if I need to instead of the coolant temperature sensor turning it on or when the air conditioner is on. I would rather have control of that sometimes

[@TravisTellsTruths]

Fantastic video.

[@WanderlostOverland]

Thank you very much!

[@JAM76ER]

Nice. Thank you.

[@WanderlostOverland]

You're most welcome!

[@garykreutzer1239]

I going to install 6 lights(50, 30 and 4 pods) on 4 circuits. Should I run a #10 to a buss bar and tap off for the 4, or just run 1 wire and pigtail the relays from it, or run one 12 ga from the battery for each circuit?

[@kabandajamir9844]

So nice

[@WanderlostOverland]

Thanks

[@tomasdabasinskas8977]

Thanks a lot!

[@WanderlostOverland]

You're welcome!

[@BoomingCreation]

Coming from a power source on the switch side, what size wire would be recommended since most of the current is going in thru from the battery

[@edwardcarlin1]

Hi! Can I run 24 volts from 30 to 87 and 12 volts on the trigger (85/86) switch? I'm planning to install a 24v airhorn in my car and I just bought a 24V boost up converter.

[@White_buffalo_4r]

very descriptive thank you very much

[@WanderlostOverland]

You are most welcome

[@gabe8976]

Can you have the in-line fuse between the relay and the accessory, rather than between the battery and the relay? I was gonna go battery - relay - circuit breaker - accessory fuse block

[@WanderlostOverland]

Then your relay won't be protected from surges.

[@brennanpaucke2066]

If you have multiple lights, do you just splice them together before connecting them to the #87 terminal on the relay, assuming, combined, they're still less than the max amperage of the relay box?

[@WanderlostOverland]

Yup.

[@jrmcdaniel9729]

What if I have a "dual function switch"? For instance, meaning a switch that does an "up" and a "down" function? Is it ok to hook up both function wires to 86 and it still perform correctly?

[@RedEyedITguy]

They're called "spade connectors" and a "fuse tap."

[@stevenvision3612]

How come some wire harnesses have the power for the switch from the fuse going to the battery? While some do the add a fuse?

[@ll-GUTZ-ll]

Would I be able to do this with a starter relay, and would I have to wire it straight to the starter?

[@argentosebastian]

Do you know the color code for the different connectors in the relay?

[@JaceD4V1S88]

so im trying to connect a horn to my security system, i have one wire thats 12v for the beeps when i lock and unlock, and another 12v wire that pulses the horn when alarm is triggered, i need to connect those two wires to a relay that goes to a single wire to the horn so the horn does both functions. the honk when i lock n unlock and pulse when it goes off. which relay would i use?

[@vansonmafeet734]

Okay, so the LED lights I bought for my vehicle came with all the necessary wiring and a relay. I ran the black wire from it to a good neg grounding point. I ran the red wire w/ inline fuse to the +pos terminal on my battery. I've blown 2 15amp fuses trying to test the lights 2 different times. What gives?

[@WanderlostOverland]

Likely a short in the lights.

[@Coolmaaaaaan]

I have a 12v4bt-1m relay laying around and I want to know can I use this for a 12v car air horn? It doesn't have 85,86,87 and 30 just 1,2,3 and 4 written on the relay, It came with the lug with it... 1 for red, 2 for black, 3 for blue with white stripe and 4 is yellow.

[@willyacevedo605]

Instead of lights how would I wire in my starter? I'd like to use my cargo light switch as an ignition kill switch.

[@paulacabbo466]

for most applications you want to get a normally open relay

[@TheBlueBikeDoyle]

Awesome big thanks

[@WanderlostOverland]

Thank you too!

[@TheMgd2929]

Does it have to be ground to metal under the hood?

[@WanderlostOverland]

It needs to be grounded to the chassis or body anywhere on the vehicle.

[@miomine3527]

Should you add a relay to a power window conversion kit..

[@WanderlostOverland]

Depending on amps and wire size I would say probably yes.

[@dampainter1]

not sure about using an add a fuse on my fuse block, i am at the moment for the ditch lights i just installed on my 2016 tacoma....the fuse box cover won`t go back on with the add a fuse. may have to rewire and go to fuse block under the hood. i used it for the "second" wire used for dash light on my aftermarket oem looking switch.

[@WanderlostOverland]

There are covers available that allow for the add a circuits.

[@dampainter1]

@@WanderlostOverland link for covers?

[@p2o8wer]

Do I have to run to the fuse box? Can I run the switch straight to the relay 86?

[@geoffreydlin8043]

There are two things I don’t understand. If we add auxiliary lights, cooling or whatever… How do we know that it is not over taxing the charging system of the vehicle itself? That is, when is it too much load on the floor later? If you use a circuit extender into the fuse box and add amperage to it, the wire running to that circuit is still of a certain gauge. How do we know that we are not overburdening it?

[@geoffreydlin8043]

Alternator! Not floor later

[@mastro3084]

So one wire of the switch is grounded to the body and the other goes directly to the relay?

[@WanderlostOverland]

Nope, connected to a positive then to the relay.

[@bigrocket97]

Where should I place the “add a circuit” for a pair of ditch lights?

[@amitabhasaha9784]

Do 5 pin automotive relay requires an additional diode?

[@gauravjaiswal5354]

Greetings! Can we use 12v 30amp relay in place of 12v 40amp relay? Plz guide.

[@WanderlostOverland]

Sure

[@glasshalffull2930]

Actually, it depends how many amps on that circuit. If your circuit has the loud 400 watt stereo, that draws 33.3 amps (amps =watts/volts, 400/12= 33.3 amps. ) and you’ll possibly burn out the relay.

[@Hamad.Kuwaitt]

Thanks 👍

[@WanderlostOverland]

No problem 👍

[@Luui2x]

can i do 40a mp relay with a 30 amp fuse and 20 amp switch?

[@glasshalffull2930]

Sure. As long as the circuit doesn’t exceed the 30 amp fuse because it will blow. Each component you listed, you gave an amp rating and that is the ‘max’ amp it can operate and not fail. They can operate below this level. Soooo, the question is what amperage is necessary to drive whatever equipment you’re adding to your vehicle. Just like a lightbulb, the equipment you’re adding ‘should’ have a wattage (power) rating. The simple formula you need is Watts = Voltage x Current (amps) As an example, let’s say you’re adding a 300 Watt stereo. 300 Watts = 12 volts (car battery) x unknown current. Rearranging, current = 300 / 12. Current is equal to 25 amps. So, the switch which only carries a few amps is fine. The fuse won’t blow and you won’t damage the relay. The only question is what size (gauge)wires to run from the battery to the relay (pin 30) and from relay (pin 87) to your new device. Google automotive wire amperage capacity chart. This chart will give you what gauge wire to use for your particular amperage and the length of run carrying this amperage.

[@Luui2x]

@@glasshalffull2930 thank u so much for ur time

[@glasshalffull2930]

@@Luui2x You’re welcome. What upgrade are you installing?

[@vernwhitecraft2315]

Can I jump 30 and 86 together?

[@DD-Aerial-Photography]

What lights are on your rack

[@vahagnmelikyan2906]

What's the name of these relays that switch from one to another?

[@mohammad45h]

سلام سپاس وهزاران 👍 استاد گرامی لطفا در مورد سیم کشی جامع و کامل و تقسیمبندی کلی سیمکشی اتومبیل ها وتقسیم بندی تفکیکی بخشها بصوری که بتوان در تشخیص سریعترین نحوه عیب یابی کمک نماید زحمت بکشین ممنونم ...منتظر پاسخ ونتیجه شما هستم...👌👌👌👌👌👌👌👌🙏🙏🙏🙏🙏🙏

[@laurenr4797]

How do you determine the in line fuse amps?

[@WanderlostOverland]

Assuming all the wire, connectors, and switches are sized for the same, the fuse is sized slightly larger than the draw from the lights or whatever you're powering.

[@anonymousperson4363]

A spade connector is the first connector.

[@ceyhankaracolak40]

Ustalarım bende laguna1 volvo motor 140 beygir n70 motor şu tankkı yanında iki tane siyah kutu içinde reley role bunların numaları aynımı olacak bunlar birı benzin rölesi biri bobin rölesi biri bunları kaç anper kaç numara olduğu anlatabilir mi tesekkurler

[@vernwhitecraft2315]

Why on the relay is 30 a power input and 86 is also a power input?

[@Hiker97]

30 is the power to the relay from the battery, 86 is power from the dash switch.

[@UNO3598]

I am 12 in my honda they are fog lights they dont work i got new switch but the fog light only work when i connect 2 wires and it gets heated plss help me i think my relay is fine i need more explanation 😢❤

[@davidyj9013]

Have yet to see anyone address the dilema of why the schematic embossed on the side of the cover shows one of the contacts labeled as 30, but then the actual spade terminal (or pin) is marked 87a. They are the same!

[@WanderlostOverland]

Nope; 87 and/or 87a will be connected to your controlled accessories that you wish to turn on and off with your relay. 30 will then be the pin connected to your battery power.

[@Faknm]

Man I am sooo lost lol I need figure this thing out…..

[@kernchapman]

Think of your relay as a switch....that gets turnes on....

[@vahagnmelikyan2906]

Nvm found it😂

[@kenhogan1433]

So am I right in thinking that 85 and 86 are the low amp side switching the high amp live through 30 and 87?

[@jorgeluis1588]

Can a relay be used with a reverse polarity switch ?

[@WanderlostOverland]

sure