Wiring a relay: How & Why You Should Use Them On Your Project Tech Tip Tuesday

Whether you are building a cruiser, a racecar, or a bruiser. Using relays in your wiring can improve the performance of whatever component is wired to it (such as a fuel pump, a fan, water pump, and more) as well as make the wiring more robust, durable, and functional.
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[@larryharrelson2540]

This young man has his "stuff"laced up tight. He's good at what he does and doesn't mind teaching others who are not as well informed.

[@najstephy5565]

such an underrated channel! thank you for that, very nice!

[@orionsmith9645]

Literally the best video on this I've ever seen. Currently wiring my truck, already knew how to use and wire a relay, but this video was great.

[@snake_eyes_garage]

The wire gauge vs. length is key. Previouslyr I didn't know that you can get away with a smaller gauge wire over a short distance. Those Derale fans come with small short wires - and people would think, 'I just match that gauge' to run the wire to where you need to go, but in my measuring I needed a larger gauge. Maybe why a lot of people complain of their electric fans not flowing enough or prematurely failing. Your built in light location is awesome!

[@BALLERXD24]

What gauge wire did you use on the derale fans?

[@snake_eyes_garage]

@@BALLERXD24 8 gauge copper stranded wire. If you search the web for 12v wire gauge distance voltage drop - you can calculate the specs needed for your application.

[@MichiganRay]

8 Guage is large wire. Like for a starter. You mean a # 8 wire?

[@snake_eyes_garage]

@@MichiganRay Sorry about that. Not sure why I typed 8. I ran 10 awg from the fans to the fan controller and battery junction. I like run 4 awg to my starter which I'm sure is overkill but I assume 200amps. But yes, you can't trust anything on the internet these days. 😅

[@travismccullagh5460]

After many years of learning and using relays wrong. This video made everything very clear.

[@mikehastings4357]

awesome video and explanation of how to properly use relays to cure voltage drop problems. Thank you!!!

[@westmaingarage2944]

These Tech Tuesday’s are the BEST. Relays always challenge me a bit. Thank you for this Doug!

[@mghoward74]

??????? WHERE ARE THE LINKS YOU SAID YOU WOULD ADD. ??????

[@bwj1158]

Very good lecture. I really appreciate the info that you shared. Thank you so much.

[@paulcarter2907]

This young man clearly knows his stuff..It's always been a dark art to me, but this does shed some light on it..Thank you..UK

[@larryharrelson2540]

Ditto

[@BADQ]

Mate thank you, you are a legend. I have always get confused with relays but the way you explained it has now been implanted into my head and no longer have an issue. Champion! thanks again

[@theamickfamily6273]

Thank you for clearing up this issue for me Doug. I’ve been dreading a wiring problem for a little too long because the relays and wiring were pretty intimidating. But this clears up a lot of things for me.

[@yoelb13]

BY FAR, BEST VIDEO YOU WILL FIND ON RELAYS--TYPE, FUNCTION AND WIRING!

[@that_one_maxima]

Thanks for the great videos. Very informative. I could never understand what a relay was, but you explain it so well. I will use this relay for my fuel pump when I install my EFI while I consult your other videos.

[@glampstronzartonalbee3097]

this was VERY helpful, wiring can be very intimidating and this made a big chunk of it make sense. thanks guys!

[@JubeeHS13]

Great info this is helping me as I'm building a engine harness from scratch, and I actually incorporated a relay fuse box on my harness. I added it for ecu, accessory and fuel pump.

[@tomstanley7772]

Well put. I play with relays all the time. And I still learned something. Thanks...

[@bigjmacg]

Your best tech tip Tuesday thx 🙏🏻 so much.

[@thomasgena9365]

Thanks for a nice, straight-forward video, Doug.

[@928rcs8]

Who has the guts to even dislike this video? Man those tips are the best thanks motion raceworks

[@philb5593]

Currently in the wiring struggle on our 1/4 scale tractor. I think I've got a good handle on relays, but figured I can always learn more. This video is great, thanks Doug.

[@slvrbullet6]

Great info... the MSD 7564 solid state relays are great compact and easy to wire. 4 in 1 relay

[@ronlemon640]

Really cool video. I'm just starting to do some wiring on my project and I'm not very sure how all this works as a whole. You explained many of the questions that I had to begin with. You did very well in explaining why as well as how. I appreciate you taking the time to put info out to people like me. Thanks again and have a great day. My project is a 406 sbc powered ranger should be fun!

[@jimgoss9026]

finally really understand relays!!! Thanks for the explanation for us simple folks!! You got my sub!!

[@juiced71]

Spot on! Get them relays as close as you can to whatever your powering up👍🏻 It’s definitely nice to have nice long pig tails for the relays my old relays had fuses in the power feed.. they do have 100amp relays that you can wiring in as key on or key off definitely I nice option 👍🏻👍🏻👍🏻

[@paulmitchell8005]

Another good video thanks 👍

[@murphy3999]

That all made great sense. You explained that well thank you. What happened to link to wire diagram?

[@scottlarson9348]

Awesome educational video. Really well explained.

[@240SSONLY]

Great knowledge for the enthusiasts, Thank you.

[@jamesford7182]

Some things to take into consideration: Length of wire in a circuit includes + and -. Remember when calculating voltage drop. Design each circuit for 25% additional load over the fuse or circuit breaker rating. Avoid any high amperage equipment in the passenger area. I strongly recommend GXL or SXL crosslink polyethylene coated wires. Use IP67 rated enclosures for your components rather than that marine grade crap which offers little to no dust or moisture protection. Prewired relay sockets force you to use wires that are all the same colors which hinders repair. 87A is on DPDT relays. It is had never been used in SPDT relays. DPDT relays may be rare to you but they are not rare at all. Often used in interlock systems where you want to shut something off when another is switched on. Relays and be bought with a resister or diode on the coil circuit to protect electronics from surges. Micro relays can switch up to 40 amps and use the metric 280 configuration blades, terminals, and spacing. Amazing space savings can be achieved. High power relays are great for switching loads of 100 amps but, the safest way to wire the system is to go directly to the starter motor through a battery switch like a Cole-Hersey M750 and then take power from the starter for your system. This not only will keep maximum loads off of electronics but, will allow you to crank the engine without energizing anything else for compression checks, etc. I learned some hard lessons about automotive wiring in 50+ years since 1972 when I first got into drag racing. Got out of racing but have been in the industry one way or another my entire career in manufacturing and dealer support. Just retired last year so I actually have time to watch videos on the subject (I had no desire to "entertain" myself on off time with work related stuff). I thought your presentation was much better than most I watch. Obviously I don't totally agree but certainly enjoyed a video on the subject that didn't make me laugh. Anyway, I hope you are keeping up your good work as I see this post is four years old. I'll bet you have learned a lot since you posted this. I was learning new things even as I retired and I loved every minute of it. Did you know that 3M did a white paper on electrical tape flagging? I found it to be a good read, believe it or not. Checkout the 280 footprint stuff. It is actually very cost effective. You can pick out an IP rated enclosure that is an open grid. Then you can populate the enclosure with any 280 component like, fuses, relays, jumpers, etc. I used to make a 3.33" x 4.44" load center that contained 10 fuses (or circuit breakers), 5 relays at 30 amps, all of the seals, terminals, cavity plugs, brackets, with 10' wires for each input and output of the correct size if GXL wire for a total cost of $73.72. The finished product was IP67 rated and could be power washed. It took about 30 minutes to assemble on a normal day. If I didn't need all ten circuits, no problem. If I needed more I also had made up some two circuit relay block and five circuit fuse blocks in advance. Since I already knew what basic circuits I would be using regularly, most of the wire I used as function coded every 6" with its name and number. The additional price for that is included in the cost I gave. Be advised, there is a big learning curve involved with this method but, if you are going to be doing it for a living, your reputation is on the line with each and every thing you do so do it right. It will make the next major advancement that much easier.

[@user-ew9rm1py2v]

Very good and informative. I now truly understand how relay works.Thank you

[@angry408w7]

excellent video thanks. you guys are helping me build my car.

[@davidcobb4527]

Thanks for the vid, very informative. Answered a few questions I had concerning wiring up a couple halogens on a pontoon build using relay a relay.

[@509camaro9]

12 volt ninja! Great info guys

[@kevincrawford6864]

Thank you for the knowledge simplification.

[@hankhessig6586]

Good explanation Doug

[@kenord3437]

Thanks very much mate, explanations were great, you have helped me understand how to wire my project, greatly appreciated. Ken from Australia.

[@MrLangleylad]

Great video, thanks

[@joecarusi4320]

This is going to help me big time on my 1969 Nova.

[@roberthowland4503]

That was really a good explanation of what I wanted to do. Thanks

[@vthunda]

Great video. Appreciated the discussion and the appropriate uses for it.

[@rezagrans1296]

**Plz plees help☆ How do i tie more length of wire to the short red/black+- stubs that come with the universal 12V electric pump ive bought? What gauge wire do they jineraly use? The two short wires coming with it are not long enough to connect to a 12 V auto battery i woud have placed a safer 8 to 10 feet from the tank. Trying to jrain out bad fuel-tainted gasoline from a 2000 pon-iak sunfire faster way than those dum flimzy hand pumps. Txs a million

[@mikeymasi]

Just to clarify what you said about PWM, it doesn't exactly give you different voltages but instead gives you different duties. So for instance it will continually cycle from +12V to 0V hundreds or thousands of times per second and based on the commanded duty (0-100%) will determine the split between how long the pulse width stays at +12V versus 0V for each cycle. I'm just using +12 & 0 as nominal voltages here but think of it as high & low voltage depending on the application.

[@censored1360]

Excellent Video, I needed a refresh on car wiring specifically my electric fan set up and FI system. Exactly what I needed for the next steps on my 1970 442 revival after sitting in my garage since 2005. Feel free to send donations lol

[@adamaugust9190]

Love this video thank you!

[@larryharrelson2540]

Thanks for sharing this bro. You done Good

[@One.--]

I was working one with helping a friend who's a painter that said he is constantly blowing out his dual paint sprayer pumps. First thing I notice was his 100 ft extension cord 16 gauge & motors was so hot it would burn your hand😮 After buying the correct gauge extension cord 12 gauge he was good to go. He had a huge voyage drop. The lower your voltage goes the higher the amperes are the motor are toast😮

[@gregscheyd4131]

THANKS , ONE !!!!

[@gregscheyd4131]

NOT POSITIVE , but I think what you meant to say was the LOWER YOUR RESISTANCE , THE HIGHER CURRENT FLOW .... thicker Guage wire has less resistance and is more CONDUCTIVE ....also the extension cords probably don't want to be EXCESSIVELY LONG .... only what 's necessary ....

[@lonnieairsman9215]

Cool video very educational thank you

[@m.scottmunger4685]

Well done. Thank you so much.

[@brucenilssen1235]

Great video. Thank you

[@Boostedm3nace]

Thank you so much. This information would have solved the issue I had with supercharger m3. The secondary pump wire kept getting hot, until it eventually made the connection fail multiple times. Looking back, it was 100% because of the thin gauge wire that was supplied in my kit. I do miss that that high revving v8 sometimes, but it doesn’t hold a candle to the smiles per gallon I get with my manual hellcat.

[@licha5050]

you're the man! thanks

[@Thumperr6]

Thank u finally got the answer I was looking for

[@NoName-pp3kj]

excellent video!

[@carpentryconcepts2669]

verry helpful info about relays now i can wire up this electric fan correctly .... thanks bro

[@joecarusi4320]

Explained vary well thank you your help was great 100%.

[@chunkafunk81]

great explanation! thanks!

[@DHRINC07]

Great info good review

[@SARJENT.]

Great vid.

[@MotionRaceworksOfficial]

Thanks!

[@claysonwebster1622]

Very informative 👍🏿👍🏿

[@white.rabbit]

Thank you so much for explaining all these in details! I'm planning to make a fuel pump kill switch for my project car, and I was thinking about cutting off the power wire for the fuel pump to insert a kill switch. However, since you mentioned the voltage drop, I realized that increasing the length of the fuel pump wire might not be a good idea. I'll probably insert the kill switch in the wire that goes to 85 (probably the ignition switch?)

[@guesswhomartin9249]

Very good... Your explanation is the best so far. At first I was thinking your wrong about 16;02 . But as I got to listen to you more, ok,,, the other videos I was listening to are wrong. Yours is right.

[@supermopar7497]

Great vid

[@IntheBlood67]

Most Excellent!

[@510Exclusive]

Iv'e used the fifth pin on a 5 pin relay to trigger a warning on the dash for a car that had a remote battery cutoff switch. The cutoff switch would drain power if you didn't hit the remote switch to disconnect the battery. I put a flashing light on the dash so when you turn the ign key off the light would flash telling you the battery is still connected and to hit the switch to disconnect the battery. But once you turned the ign key on the flashing light would go out. Was pretty cool to figure out a use for the fifth pin even if it was rare.

[@DropTopPerformance]

Awesome video man, Doug does a great job breaking it down Barney style for people like me🤣

[@MotionRaceworksOfficial]

😂 Thanks for watching!

[@ToddKing]

@@MotionRaceworksOfficial How about adding the links and part #s you said you would?

[@jesseportillo324]

Very informative...quick question. If I'm wiring three different set of LED lights would I need 3 relays. If so, would each of them have a wire going from the 30 relay connector to + battery. Please advise. Thx. Or is there a different way to do this.

[@DJSKID808]

Thanks clear defined video

[@leomasterking]

Very nice. My question is if there is power leakage or unstable power coming from the switch Will the relay compensate for the voltage and amp fluctuation?

[@WilliamVG]

Thanks for the detailed videos, really helps. Btw my girlfriend has a 2014 Hyundai Accent Sedan in mint shape but her front bumper is cracked, thinking about buying plastic welding sticks. Any idea what the plastic type is, TPO? or PP?

[@randelmalavida]

Yo did a great breakdown of all that. It is my first time ever even this and feel like I now have a much greater understanding and appreciation for the relays job. Than You

[@robvas]

The guy that wired a fan switch in my car needs to watch this. Melted the fucking thing!

[@roosevelthoward515]

Helped a lot

[@KSIXRIDER]

Thank you!

[@numbman2011]

Thanks , you are awesome But i always ask my self can i put voltage converter ( step down ) on 87 pin to make 12v step down to 6v form OEM car rear view camera ???

[@tomtee4442]

In my old muscle car at night when I would hit the brake I had voltage drop. since the wiring harness was good but it was outdated. I put relays on the back brake lights, headlights, dash lights. I also grounded the back brake lights, running lights, headlights with a heavier ground and additional ground. With relays I could cut the back brake lights off or on, tail lights off or on, and run the high beam and low beam both on at the same time for additional light since I was putting relays on everything. And hitting the brake pedal at night with everything going no voltage drop at all on gauge. Can stop the car in the road at night with no one seeing that the brake lights are on with the brake lights cut off and do a nice burnout or could street race.

[@AlvinHanson1708]

Good knowledge! I'll probably buy a 40 amp relay with a pigtail to learn more how electronic specs work.

[@SilentNight1647]

I do industrial control engineering for a living and the turning point for me with relays was realizing they are just an electrically operated switch. In school we had always been told they were a way to control a large amount of current with a small amount of current, but that never made much sense. Once I figured out it was just a switch that you could open or close with electricity it got way easier.

[@MotionRaceworksOfficial]

SilentNight1647 exactly! It seems daunting til you realize that

[@tpcoachfix]

If you have a diode suppressed relay, you must ground pin 85 and hook power to pin 86 to energize the relay.

[@cbd4734]

The relay I bought shows ground pin is 85 so I guess I have a diode suppressed relay. But what is a diode/what does it do?

[@N269]

@@cbd4734 diode is a means to unload the magnetic field in the relay coil. When power is disconected from the coil (control) then there is an inductive charge within that coil. If no diode is placed across the coil then you could have upwards of potentially 500v+. Not a big deal if straight to ground, but if the circuit is controled by a transistor/logic circuit then BOOOOOOM! Best practice is to use a diode. IN4001 is just fine between the +ve and -ve of the relay control coil. (Point the diode from -ve ->| +ve.)

[@periklisgewrgiou5327]

Thank you so much

[@censored1360]

Love this video watched it a few months ago getting up to speed planning, now I have holley efi tank in, engine and trans in and starting with running all the fuel lines and wires ect.... I still dont know the best way to run the efi fuel lines past rear axle on my 70 gm abody 442 just looked at it tonight and factory line placements wont work..but car hasnt run since 05 and getting closer most every day

[@rezagrans1296]

**Plz plees help☆ How do i tie more length of wire to the short red/black+- stubs that come with the universal 12V electric pump ive bought? What gauge wire do they jineraly use? The two short wires coming with it are not long enough to connect to a 12 V auto battery i woud have placed a safer 8 to 10 feet from the tank. Trying to jrain out bad fuel-tainted gasoline from a 2000 pon-iak sunfire faster way than those dum flimzy hand pumps

[@ctpurr2982]

With standard automotive universal relays and with resistor protected relays, control side (pin 85 & pin 86) polarity doesn't matter. But with Diode protected relays control side polarity does matter, pin 86 must be the higher voltage side and pin 85 the lower voltage side. If the polarity is reversed the relay will short circuit the control side and damage the wiring, the relay, or both. It is a good practice to always wire the control side with pin 86 + and pin 85 -. That way in an emergency you can grab any type of relay, stick it in, and you will have a working circuit.

[@vagabond3045]

So I have a c10 where I threw a lm7 in and I have now bought a cpp tank they don’t give u instructions on how to wire there fuel pump it came with a walbro intake pump to give me 60 psi I got the relay you sell but I need to know what is a good 12 volt switch to wire it to I got gauges wired to my light switch so where should I go from there also do I have to run a inline fuse this is my first time wiring

[@shaunadapettway3890]

Well, I subscribed because you seem to be an electrical Professor. Thanks for info. ? Can you tell me if a wire is ran from relay slot to inside fuse box to enable car to start? It was sold like this.

[@christopherleonard6433]

Can you explain how to wire this relay into the starting system? Bought a 66’ mustang that had this installed and removed it. They used the neutral safety switch wiring and the S terminal wiring for the starter solenoid.

[@ramrodou812]

very well done video!! to clarify, you'd want to wire the relay close to the device you are powering? did i get that right?

[@censored1360]

I only watched because you do Cleetus content. Thanks for the Bald eagles

[@uneducated_immigrant]

What damage can be done by bypassing the relay and wiring directly two pins on the relay? My headlight high beam is not working, but if you bypass it, it's work.

[@curtthompson2787]

So on a 5 pin, is the center used to run a second component? Is it always on or does it turn off when the main one turns on?

[@rothe31]

Relays are simple. I always do them this way 85 = trigger input. 86 = is the opposite of what you are using as a trigger. 87 = should be what you want as your output. 30 = your output. 85 and 86 are interchangeable, you can use 86 as your input trigger you will need to use the opposite on 85. If your trigger is negative (ground) then you will apply 12v to 86 (or 85 if you used 86 as your input). If you are needing 12V out of the relay (pin 30) then you will apply a FUSED 12v source on 87. SO if you have a negative input (85) and you want 12v out of the relay(30), then you would put a FUSED 12V on both 86 and 87.

[@bryansaull7554]

It would help also if you could mention the recommended wire cross sectional area to amperage usage so guys use the correct wire gauge.

[@MrOlred77]

Always use the same size wire if not 2 gauge sizes bigger, depending on your applications and distance between the relay and the battery..... d/c and a/c currents only have one thing in common, they both flow outside the wire not through it.... but thats a different story for a different time..... just like anything, resistance in an electrical system is bad there has to be some sort of balance..... the better the balance the less heat you are gonna generate the more resistance you have the more heat you tend to generate...... so much that, like he says in the video, eventually the wires can't feed or hold the capacity of said or required voltage, either blowing the fuse or causing a fire from melt down of an overloaded circuit..... also, the same goes for grounding situations..... one of the most commonly overlooked things is grounds...... the shorter and bigger the ground, the better and more solid connection will be for your systems..... one thing I've always believed in personally for my own self is always run a ground cable one or three sizes bigger that your positive leads that is required for your system if there's not a place to ground to in a short amount of distance...... last but not least..... soldering is a must for any high-end electrical system the less connections in the circuit the better and less resistance you will have..... in some instances if you wanna use crimp connections.... dont... those are for lazy people that do shit half assed or in emergency situations just to get themselves going in a pinch..... not mention they look like shit......or sometimes its the only thing folks have to get things done..... sometimes beggers cant be choosers..... remember the rules.....measure twice cut once.... do everything right the first time so you ain't sitting on the side of the road at 3am wishing you done it right from the beginning...... 😉 🤙✌

[@shanemiller9307]

Your a tank of information

[@SSTools1]

Where are the links? Great video but was disappointed at the end when I went to look for the links you spoke about..

[@ToddKing]

Me too. Very frustrating.

[@jimhiscott2918]

87a works great for your home wire on your wiper blade motor

[@StephenGiovi]

Some older cars have relatively low voltage in their system, hence, amperage running thorough the system. How would the relay be wired to maintain the amperage/voltage to a new-type distributor?

[@jcnpresser]

Man thank you for showing how to properly wire a relay. I was watching some videos awhile back and come across a guy with a pretty successful channel and man he had it all wrong, wire the coil side straight to battery and ground, wtf. And wire on side to pcm and other to fuel pump. Omg. I quit watching and went to the comment section to see if anyone called him out on it and 1 guy did and that sob was so smug like yeah I don’t know what doing sarcastically, yeah buddy ya don’t, like you said he could cause someone to burn something down or fry a pcm, I hate idiots. You guys rock. Oh got my new flag hat from you guys and it’s awesome, I think my dog could smell y’all’s cause she was going nuts, or maybe all the freedom!

[@homelessvet2900]

Hey Doug, learned me some knowledge. I was using this MP 1050 double relay to power 2 fuel pumps, a 4303 as my secondary (hobbs switch controlled) and a smaller bosch pump as the primary for my turbo LS. So going to order another 1025 to run the smaller pump and wire the dual relays to feed only the big pump. My question though; throughout your video you keep saying 40 amp relay, but the 1050/1025 relays are actually listed as 30 amp relays. Did you just miss speak or are they listed incorrectly?

[@78freewheeler]

He touched on it about mid way through the vid. But most relays are 40amp on the NO (normally open) contacts and 30 on the NC (normally closed).In this case 30 to 87a is NC and 30 to 87 is NO. It’s also common practice (at least in years past) you can use a st85 solenoid. Which is a 80amp continuous duty solenoid that would be used like a starter solenoid on a ford etc. it is essentially the same as your standard relay just with a greater amp rating on the contacts and you only have 1 set of contacts. But super simple to wire. Your small studs would essentially be 86 and 85 on a standard relay and then your large studs one would be battery positive and the other is load side (device to receive power)

[@blockequals4]

What’s the best way to tie into the factory key switch? A) To retain the factory power distribution, and B) to activate a key on12V distribution block from the main cutoff switch with say, a 2 or 4 gauge wire feed? Thank you!

[@laneeric]

Most vehicles have an open (unused) power on when ignition switch is on terminal. Mount your relay as close to the component as possible so the heavy gauge (2 or gauge wire) are short (thus allowing the most amperage). The "trigger" line, in this case the 85 pin can be any gauge you want, it's not providing current, only a trigger voltage.

[@VietPho]

12:50 thanks! 21:20 Nice Dog

[@blakenorman4822]

So you run thick wire from your battery and use relays, will a single battery and alternator be enough to run two fans and extra fuel pump and water pump by itself?

[@jimhiscott2918]

I was under the impression runnig the solonoid closet ti the fuel pimp, fan etc was the best wat to go?