Advanced Relay Tutorial: Swapping a Positive for Ground (Example 5)

www.hournineracecraft.com/relays.html
Pin Layout:
Pin 30 is connected to the device that needs a ground connection.
Pin 85 is the positive signal from whatever device that switches the (+) connection on and off.
Pin 86 is the connection to ground.
(Note): Pins 85 and 86 can be swapped.
Pin 87 is the connection to ground. When the relay is triggered then pin 87 will be connected directly to pin 30 inside the relay.
Pin 87a is unused, this pin will connect to pin 30 while the relay is in the OFF position. Using this pin will only result in the device that needs ground (connected to pin 30) remaining on when the relay is turned off.
The end result:
The relay will power on your installed device by switching the ground on. This happens once a positive signal is switched on automatically by your car or motorcycle.
Disassembled Bosch style relay
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#leds #led #ledlights #offroadlights #foglights #rooflights #wiring #electrical #relay #relays #electricalwork #solder #soldering

[@RobertDickens2002]

I watched 3 different videos from another guy all supposed to be explaining this and your video explained it without even having to actually watch the video

[@emilyramsey9079]

Very well explained young grasshopper 🎉. Excellent job.

[@kaithemotorguy]

I just wanted to take a minute to thank you for making this video. I needed a way to control the engine ground connection on my racing mower setup and this video helped tremendously. I'll be posting my racing mower video soon and will be sure to link this and throw you major props.

[@LegitRaceCraft]

Awesome! Glad to hear it helped :)

[@craigp8430]

Your videos on relays are excellent, concise and well presented, thank you for this.

[@ricerkt88]

Nice job... makes relay wiring easy.

[@faisal6232]

Thanks dude, it helped a lot. Keep making more useful videos.

[@JoeSpivey2]

I had a computer solid state device go bad that operated the door locks, siren, headlamps etc. when the alarm went off. I only needed the door locks to work. I needed two relays to switch the power to pin 30 when I hit the power lock wires to each of the five door locks on the, "A" side wile maintaining a ground to the "B" side wires. I need the power and grounds to reverse polarity when I hit the power door locks to the lock position and then give power to the, "B" side and ground to the, "A" side. I tied power to both of two relays on pin 87, constant ground to both of the two 85 pins on both relays. I tied constant ground to the 87A pins on both relays. I used power, "A" from the down lock side of the switch to turn relay, "A" from a constant ground to a momentary 12v for wire stack, "A" (Applied power from the down switch to pin 86 of relay, "A" , relay, "B" continues to feed ground to wiring set, "B". When I release the lock switch both relays are again grounding. When I press the unlock button it sends power to terminal 86 of the, "B" relay which sends power to the, "B" stack of wires while the, "A" stack continues to be grounded. In short: two small 6 wire bus bars, two relays and I was able to control the power locks with no solid state wiring. This trick also works for window motors and for electric antennas for radio, (radio only gives one power wire to the antenna motor. I split that one wire and wired it to two relays. when power to both relays have power applied to terminals 86, (with 85 being constantly grounded on both relays) one Relay, "A" transmits ground from terminal 87 to terminal 30. The other relay, "B" transmits 12 from 87 to 30. When the radio shuts off and the power to 86 no longer exists both relays return to normal where relay, "A" has a 12 volt power on 87a and relay, "B" has a ground on 87a so the antenna goes down.

[@bradwinter156]

At 7:30 you can use that to ground out a stator on a CDI ignition

[@Miata822]

Many automotive relays also contain a diode across the 85-86 terminals in parallel with the coil. This diode prevents voltage spikes that can damage or confuse the ECU. On relays with diodes the 86 terminal will almost always be positive. Always check the diagram for the specific diode you are using.

[@guilhermerodrigues6214]

Very good point!

[@foreverwood1963]

Ok HourNine yes this is advanced because I am now confused. I have a basic understanding of relays. I try to keep it simple so that I know where power should and shouldn't be and why. I'm currently working on my wife's 2004 acura TL that is a no start. I originally thought it to be the starter and even removed the starter , but subsequently bench tested it and found it to be working. Here's my basic understanding of relays. She has a 4 pin starter kill relay that had 123 ohms between the coils and 0.6 ohms when powered between the switch. Pin 87 is wired directly to the solenoid I tested it by sending a small amount of voltage 3-5v through the wire to make sure since I'm getting crazy readings according to me so I wanted to be sure. Pin 85 I can not sense anything there. Pin 86 shows power in the start position. Pin 30 also shows power but only in the start position as well. Pin 87 I forgot to say is also showing me ground. My understanding is that I should have a constant feed on 30, power on 86 in the start position, ground at 85 and power at 87 once 86 has been energized for the ignition thereby closing the circuit with 30. I know that I can't have the coil complete without a ground and thus I have a problem though I'm not in Houston. I hope that this might jar something for you because I'm pulling my low crop hair out. I've bypassed the clutch switch to see if that was the problem, but to no avail. I did start it remotely and it does crank when power is placed directly to the solenoid. Somewhere in your tutorial my answer probably lies. I had zero understanding of a relay having both a negative at some point and a positive at another on the same pin. Any ideas?

[@SWFLJetSkiRiders]

Nice man thank you !

[@ronf4308]

My AC relay has been permanently grounded to keep the compressor on all the time. I would love to see both a diagram and also a video or how it is literally done.

[@pd2865]

I have a dilema. I am wiring a electric fan. here is how I wired using the negative to the thermastat sending unit. From positive battery post through fuse to pin 30. Pin 85 to the temperture sending unit. Pin 86 to a switch that gives power when it is turned on. Pin 87 to the electric fan. The electric fan ground to the negative battery cable. I also y- connected the Pin 85 so it goes to the temperature sending unit and a switch to override the sending unit. I have not connected the sending unit and it is not grounded. I turn turn the switch on that grounds Pin 85, and I get power to the Y wired going to the temperature sending unit. The Problem: When I give power to Pin 86 I have power to Pin 85 on a test light. Why?

[@LegitRaceCraft]

Pins 85 and 86 should only be used for power and ground to turn on the electromagnet which connects pin 30 to 87. Why is pin 85 connected to a sending unit?

[@jaked5651]

I want to be able to kill brake lights. Not I can use an indicated switch to kill ground, and when switched off, everything is normal.

[@LegitRaceCraft]

If it were me I would wire the ground through pins 30 and 87a, so that the brakes work when the relay is in the "off" state. Then when you flip the relay on via pins 86/85, the relay will turn on and shut off the ground connection to the brake lights (and all other grounds that are being shared with the brake lights). Consult your wiring diagram before you do this though, you'd want to see what all shares the ground with the brakes

[@dadadadada4974]

Excellent video! I am trying to do exactly what you are doing starting at 4min. Does feeding the positive as signal into relay cause any extra load or ground issues on the circuit you are tapping into (the circuit you are getting signal from)?

[@LegitRaceCraft]

No, the relay draws such a low amperage it is hardly even noticable. Depending on the relay it only draws 200-800milliamps

[@raldgeworkz614]

Thank u idol

[@UptownFights]

Ok. Have difficulty time here. I have a boat and I'm wiring in a 1 wire distributor getting power for ignition switch, but I need it to cut power to distributor when shifting and the boat has a safety switch that used to do this for coil packs, but no longer use thats why I've now have distributor. The safety switch is open, until shifting and it is momentarily grounded. How can I use this to cut power to distributor.

[@LegitRaceCraft]

5 pin bosch style relay. First off, I'm not familiar with boats and how they are wired, so take this with a grain of salt. One possible way would be to wire the distributor signal through pins 87a (out) and 30(in). Then wire pin 85 to the ground from the shifter and 86 to a normal positive wire. This would allow the relay to shut off the distributor power when the ground is connected. Don't connect anything to pin 87 though, pin 87 will be "on" while pin 87a is "off"

[@sharewithraj]

I need to make a car clutch that disconnects (a 12v ground circuit) when the pedal is pressed can it be done with a relay? Pls help..

[@LegitRaceCraft]

Thanks for the comment. I actually have a relay on my car that I wired in to my clutch pedal similar to what you're saying. Email me and I'll send you the diagram I drew up for mine, my email is HourNineRacecraft at Gmail. There is generally a clutch switch for the cruise control that disengages as soon as you start pressing the pedal, and a clutch switch for the start system that is pressed when you press the pedal to the floor. Which are you hoping to use for your situation?

[@angelhurtado4870]

You have it backwards... Thirty is normally the input...when off it always is connected to 87a until triggered by 85/86. So you have it backwards. After being triggered it connects from 87a to 87

[@LegitRaceCraft]

The idea behind the video is to teach someone how it works. Not how to wire it correctly. I was lazy in this video though, this drawing is a modification of a diagram that requires me to wire pin 30 as an output, that video is called "dual power source switching". In all actuality though, it doesn't matter how you wire it if you know how it works inside. I've seen them wired a few ways in factory applications, it all depends on how it is being used. Wiring pin 30 to power isn't a requirement unless you are using 87 and 87a to switch between two things being powered.

[@ichoozjc]

@@LegitRaceCraft Yeah your video is perfect for my application. I am wiring in a failsafe for an AEM meth injection kit. Basically I have a ground coming in to 30 and out to 87. When 85 is powered I have a closed ground connection. When 85 is grounded (AEM failsafe) it opens the ground connection. Ground is for.my IAT sensor. When it is open the.pcm reads it as -40°f. Then I simply tune the pcm to pull timing when it sees that temp. Keeps things safe.in the event I am at the drag strip and the meth controller fails. Thanks!

[@Tankgeeman]

Can you help me hook up my doorlocks to two relays

[@pablogomez7519]

I'm using a test light and checking port #86 and nothing when I turn the key and I'm not getting a light when I put it in port #85 (yes I put it on the positive terminal)

[@LegitRaceCraft]

I would check the fuses. The power will fall behind a fuse of some kind, and either you have a bad wire or the fuse has blown.

[@pablogomez7519]

@@LegitRaceCraft fuses are all good. I put a wire In the connector 85 wich is suppose to be the ground I removed the bottom of the plug from the fuse box and it shows the purple and white wire so that goes straight to the NSS. I wonder if the switch is back that's why it doesn't light up🤔🤔

[@1BOSSman760]

is pin 86 and 87 connected?internally?does it matter what i have on pin 87 positive or ground that would send what ever i put on 30?

[@LegitRaceCraft]

86 and 87 aren't connected internally. They are separate circuits. 85/86 is just for the electromagnet that pulls the connection for 87/30. And yes, whatever you have on 87 will connect directly to pin 30. I've run ground across them or power

[@jesseanson5690]

How do you hook that up to a switch for it to come on with high beams

[@Brendalo1]

I would like to turn my car on then have a three position switch, position 1 off position, 2 running lights, 3 high & low beam, controlled by a foot switch with three wires attached middle hot, switching between high & low beam, I cant figure out how to make this function, I have been watching videos for hours

[@t_train3796]

I hope you figured this out, seeing as its from a year ago. For anyone else reading this, the 3rd position would send power to the foot switch (middle wire). One wire would go to the low beam relay and the other to the high beam relay.

[@corvetteshorts4670]

Here's a fun one. Im wiring a flex-a-lite fan To a cool and switch that is closed ground when cold, then at 185ﾟ the circuit opens. So my fan actually runs in reverse. Runs when cold, turns off when hot. I don't drive the car often, so I don't want to leave the relay activated to keep the circuit "open", aka not running and drain the battery. How would you wire that correctly? I am thinking two relays? One to immediately power the main relay when the car starts.

[@albertguzman9485]

I am trying to wire my brake/turn signals from scratch using relays not sure how to do it

[@kinoaskals2904]

nice tutorial!! just a question sir.. at negative(-) signal.. would it be the same if the device that needs power will be on 87 instead of 30 and the 86 and 30 goes to Bat+ or constant 12V and 87a is still X or no connection and 85 still in negative signal... like your video tutorial on 4 pin relay..?

[@JoeSpivey2]

Yes, you can certainly use it like that if the relay doesn't contain a diode between 87 and 30. In many cases relays turn on appliances that have electromagnets in them, (a/c compressor clutch is a good example). When the appliances are turned off a high voltage spike is returned through the wire. Relays with diodes protect the electrical system from these spikes. They look just like the relays that don't have diodes so you have to look at the diagram on the relay. If it has a diode between 30 and 87 then 30 must go to the appliance. If it has a diode between 85 and 86 then 85 must be ground and 86 is 12 volt. (Those relays are designed to protect the appliances that turn on the relay such as the PCM. The relay itself uses a magnetic field to apply the points and when the magnetic field from the relay collapses there IS a voltage spike!) Diodes between 30 and 87 are almost always for either the starter or the A/C and are rare. (Most vehicles have a separate diode in the fuse box that looks like a fuse)

[@marlandowner6416]

Hello, Please help! How do i wire a positive alarm signal to a ground trigger car light with a 4pin relay not 5? I just wanna know where 87a, 86, 85 and 30 connect case i tried the diagram and the lights are on all the time. I may have miss wired somewhere. Anyone please help!

[@rmjryost]

Hey, great videos. Needs some help determining whether I can make this work. Two issues. 1) I have a prewired (via circuit board) 6-relay panel. The relays appear to be wired normally with an output and ground and 8-pin connector from the switch panel. Additionally, I have the Alpine KAC-001 switch controller which direct to connect the output to pin 86. Is this going to work? I want to use the KAC001 instead of the regular switch panel. 2) Secondly, I have two items that need ground to activate vice power. Will I be able to use this prewired relay panel?

[@Rajgaragesautocares]

Hey man pin 30 is not a ground,you stated fault information 😅

[@LegitRaceCraft]

Thank you for your comment, but it's not false information. Pin 30 is neither positive nor negative. In simplistic terms, a relay is an automated switch. Pin 30 connects directly to pins 87 or 87a, nothing else. So you can wire ground through it, positive, 5v positive, etc, as long as amps and current aren't too high. As long as 87 and 87a are expected to be ground if 30 is used as ground also. It's a simple switch that's controlled by an electromagnet. I've also seen relay setups on Toyota cooling fan systems that also use ground wired through a relay similar to this.

[@Rajgaragesautocares]

@@LegitRaceCraft doesn’t make sense your statement.for example if pin 30 is grounded and pin 87 connected in positive terminal of bulb 💡is absolutely not right.

[@Rajgaragesautocares]

Pin 30 supposed to be positive for making sure for everyone

[@LegitRaceCraft]

Exactly, that's why you would connect pin 30 to ground, and pin 87 to the ground terminal of the bulb. Some situations require a ground switch.

[@AztecWarrior69_69]

What software are you using?

[@LegitRaceCraft]

Software on Linux, I'm not sure what it's called but it's an add in to the operating system. The animated picture is just a gif that I would start and stop

[@AztecWarrior69_69]

OK ty

[@ericr1035]

Greatly appreciate if you could confirm or correct these connections... "Not sure why you'd want to do it that way" (7:10).... that's what I need (Device powered ON when ignition OFF) Do I have this correct? 86 : Fuse box (in car cabin) 85 : Ground 87A: Device Positive 87 : Ground 30 : Battery Positive Device negative : Ground Application (device) is a motion activated siren I ONLY want ON when ignition is off. I'd be running an accessory fuse box mounted in engine compartment... not noted above but this would essentially be the device's negative and positive.

[@LegitRaceCraft]

Disconnect pin 87 and leave it not connected to anything, otherwise you'll get a blown fuse or a melted relay. Pin 30 connects directly to pin 87 when the relay is on, so that would be like touching a positive wire to ground.

[@LegitRaceCraft]

Also, not all fuse locations in cabin are on when the car is on and off when the car is off. I'd make sure that the fuse location you've chosen switches on/off with the ignition

[@ericr1035]

@@LegitRaceCraft Thank you for noting that. Initially I was hoping to tap into a car factory device (eg. car's alarm) that would already turn OFF when ignition was turned ON however I believe car manufactures were smart enough not to make the alarm dependent on the fuse box.

[@ericr1035]

@@LegitRaceCraft Lol! I would definitely be the person to create sparks and melt things. Thank you for taking the time to minimize the damage I'm destined to cause.

[@sticc2itgarage672]

Can you put a neutral safety switch on a ground relay to where Park and neutral has ground only in those gears

[@LegitRaceCraft]

I would need a bit more information, I'm not sure how your neutral safety switch is wired

[@JoeSpivey2]

You can certainly use a standard relay for the starter interrupt using input from the neutral safety switch/ transmission range sensor. This is already being done by almost every automotive manufacturer. Most all of them use a 12 volt reference to control the start relay.

[@tomdutcher2131]

@@JoeSpivey2 I have a 2005 Volvo v50 that won't start. I read a fix on a sweedspeed forum was to ground the Bosch 30 amp starter relay from the relay to a nut on the strut tower. I am wondering if pin #85 is the one to be grounded. Thanks, Tom

[@JoeSpivey2]

@@tomdutcher2131 Tom, first off I would bypass the relay entirely. Check for power on pin 87 and pin 30 with the relay out. The relay simply connects 30 and 87 to operate. One of those two must have 12 volts. The other should be an appliance waiting for power, (in this case the post on the starter solenoid) If you don't have power at the relay and a good connection to the activation post on the solenoid you are at least diagnosing the problem. If you do have power on one and an appliance waiting for power on the other simply MAKE SURE THAT THE CAR IS IN NEUTRAL OR PARK! and then use a jump wire in place of the relay from cavity 30 to cavity 87 on the relay terminal. If the vehicle starts then test for power on 86 and ground on 85. With the key on one will either be hot from ignition or one will be constantly grounded and the hot from ignition will be with the switch. When you have both ground and 12 volts on 86 and 85 the magnet in the relay is energized and the points in the relay will close and connect 87 to 30. (Basically the same thing that you did when you jumped 30 and 87) I hope that this helps you. Please respond to let me know.

[@JoeSpivey2]

@@tomdutcher2131 If you have ignition voltage on pin 86 then yes grounding pin 85 will close the contacts in the relay and transfer power from 87 to 30.

[@outyonder33]

How do you wire two relays together in order to power a high output device or if you're trying to run two light bars on one switch

[@LegitRaceCraft]

+z 34 two light bars off of one switch? I would use the switch to trigger two relays simultaneously by connecting the switch to pin 86 of the relay. Run two wires straight from the battery to each relay (connected to pin 30). Then run two wires from the relays to the light bars (so one wire from one relay pin 87 to the light bar, and the other wire from the other relay pin 87 to the other light bar). If your switch has a positive wire coming out of it to power the relay (pin 86) then pin 85 on the relay should be ground. Or IF your switch has a ground wire coming out of it to trigger the relays, connect that ground wire to pin 85 of each relay, then connect pin 86 of each relay to the battery. It would be easier for me to draw up a quick picture if you send an email to my KZbin email address that I think is in the (about) part of my page.

[@AzraelPercussionNEO]

Let me ask you this. I am wiring a LED light strip using a 40A Relay. I connected Battery to 30, 87 to Accessory (LED Strip), 85 TO SWITCH POWER SOURCE (instead of to ground), and 86 TO GROUND (instead of SWITCHED POWER SOURCE) what would happen if I tried powering on the LED Strips that way?

[@LegitRaceCraft]

+AzraelPercussionNEO are you just asking since 85 and 86 are switched? Most of the time 85 and 86 can be switched, and sometimes they have to be wired a certain way. Either it will work or not, it won't hurt anything with 85 and 86 switched.

[@AzraelPercussionNEO]

HourNine Racecraft I don't know if I can agree with you 100%. I don't know if it is the Relay that is doing it but it fried my White going to Relay Pin 30. Fried The 87 Wire to the LED lights and fried the Ground coming from all 4 LED Strips to a ground on my vehicle. I was wondering if maybe 40A is too much current going through a 14 Gauge wire. The other stupid thing I forgot to do was put a fure between the positive battery terminal post to the Relay. The thing is what size Amp Fuse do you need to trip the Fuse to prevent such a possible fire in the future. In theory it would seem like it worked but putting into pratice that wasn't the case wiring up some simple .2w/ per LED strip.

[@AzraelPercussionNEO]

Actually nevermind I figured out why the LED lights wheren't coming on. There is such a thing as an Overloaded Circuit which was responsible for causing the possible fire. Also is did discover something that is very important about Relays function. Also the Gauge Wire was a 14 Gauge which was too thin to handle 40A relay. Anyway. I will make a vid on this because this is something that has to be addressed and given opinions about.

[@antoniogittens5278]

Can I use both 87 and 87a at the same time

[@Ryannegative35]

hi. i need help. actually iv changed my dash board indicator light to led bulb. now it only flashes whn i turn right. n left it dose not. i need help to solve this.

[@LegitRaceCraft]

+ryan anthony without looking at it I can't help much. LEDs will only flow electricity one way, so the bulb might need to be flipped over. Is it a 194 wedge type bulb? If it is, those can be installed two different ways and you might just need to flip the bulb 180 degrees and see if that fixes it.

[@Ryannegative35]

HourNine Racecraft no no.. 1).its was a originally a normal t10 bulb(filament type). 2) a single bulb indiated left and right 3)i changd it to led n realised that the signals it recieves via the 2 cables r not positive/negative but actually reversed. ie. left signal gives black- and red+ but when i give right signal black+ n red- via same 2wires.

[@minguelitajayjay2021]

Hello! How to use relay ,horn, headlight, signal lights, and led ligjts