How To Test and Diagnose Relays and Wiring [4 & 5 Pin]

how do you know when a relay is bad that's what we're going to show you [Music] just about everything in your vehicle is either powered through a fuse or through a relay or not really powered by a relay but the power will flow through a relay which acts almost like a switch it does act like a switch but anyway how do you tell when it's bad because you pull them out you look at these four or five prongs and you go I don't know does it click when I put it in do I hear it click what's happening well we're going to dig in and actually tell you and show you what's happening we'll tell you how to actually test these things and stay towards the end because then we're going to help you on how to diagnose your wiring if it's actually not your relay what is the best way to test whether a relay is good and how do these relays work anyway I mean some of these are five prongs some of them are four prong you can even get three prong relays uh probably even more but this is probably your most common would be your four prong and five-prong relays these are all I believe they're considered all Bosch style relays but anyway they're summer five summer four and some are wide blade some are thin blades some are different configuration but they all tend to do the exact same thing and that is basically act almost like a fuse but more like a breaker and even more so than that because basically it enables you to power something without having to switch the high-powered source and before before I get that deep into it let's let's go ahead and start talking about relays and we'll get into how we power things in just a few moments now a few things that you'll probably need in this process or that will definitely help one would be a multi-beater and you can get cheap multimeters this is kind of an all-inclusive multimeter that works good on 98 of the stuff you'll need and I'll have a link in the description of this you can get this on Amazon something else that is just I wouldn't say it's critical but it comes in so handy are just these little like alligator clips and and wires and leads and you can get this 10 pack here for like six bucks on Amazon as well so just very handy to have these so you're not always having to you know take wires and and strip them and you know use the bare ends to power stuff whatever and then uh if you do this a lot or you like to power stuff with your wire leads then you can get a little bigger set like this these come in really handy Andy little more powerful alligator clips on here and they will handle up to 10 amps so again I can actually power stuff with these not just you know test whether we're getting 12 volts to something I can actually you know power up a starter motor or something like that now you don't want to load on it with something like this but still you could actually run the power to it spin the motor whatever you're trying to do with this heavier gauge and I think those are like 12 bucks so a little bit more but still these are very handy to have definitely this kit here and again at six bucks why not multimeter some wire leads and probably a 12 volt Source you could use a battery charger or jump box or something like that I'm going to use a little you know Milwaukee 12 volt battery should give us enough voltage to test these relays now let's talk about these relays and how they work real quick and then we'll actually dive in and test them now you'll have a relay that powers your air conditioning you'll have a relay that powers your fuel pump just about anything electrical in your system system if it's not a fuse it's going to be a relay that's controlling that circuit and the nice thing about the relay again is we can send small wires to it to act as the switch almost like the light switch to your house but we don't have to run that full amperage to that light switch we could just power that with low wires like uh we see right here so this could actually be controlling the switch circuit and then what's actually powering say the you know radiator fans or Xenon or LED headlights would be you know a thicker gauge say a 10 gauge wire running there that's actually doing the powering so that's what helps in these relays is again from the switch inside the car to the actual relay you're running real small wire that's easy to run and then you just run from the relay to the actual light or to whatever you're powering your heavier gauge wire but how do we tell if it's actually working or not and I ran into this here recently fuel pump wouldn't work on an old Chevrolet truck so we started running things down the wiring looked good yada yada wanted to test the relay and kind of went back over in memory how to test these relays so let's just write this out real quick and you will see this on the side of most of the relays most of the time it'll show you kind of an electrical schematic of how how this relay works well if you don't talk electrician ease then you might not understand what's going on here but let me just draw this out a little bigger here so we can talk about it and most of these are pretty much the same so 85 86 and 87. and then 87a and then we have 30. okay so those are most of the numbers especially on a five pin relay now if you're on a four pin relay then what you won't have is this number 87a right there no big deal that's fine but so if it's a four pin you just eliminate the 87a that's easy enough and if it's a five pin then you have an 87a now what's going on here is what you'll usually see between 85 and 86 is this which means there's a resistor in between 85 and 86. well that may not mean much to you either but basically this is your switch side or your control side of the circuit this is your not low voltage but this would be your lower control amperage lower load of the system and in fact there's not much load at all you're actually powering this with a you know a low amperage wire or just all you're doing is basically flipping a switch so that's what comes in one of these is negative and one of these is positive it really doesn't matter either way it's not that smart to care nonetheless so basically this is your power coming in and your ground coming in right here now sometimes uh your your e your ECU or your CPU may be controlling the ground side and or the power side so you don't always just have to check the power you have to check the ground as well but again let's talk about the the relay so we have 85 and 86 and then on a five pin what we'll have 30 is actually going to be your big power coming in and so this is your positive coming in maybe I'll draw that like this there we go so this is the positive coming in this is the this will be your heavy gauge wire if it's something heavy because some of these are 30 amps some of them are 40 amp but we can control 30 or 40 amps with this style of breaker depending on which one it is but this is your line coming in so we've got positive 12 volts of power coming in on number 30. now if it's a five pin relay then what happens is this and this is your switch and basically this means this means that when this switch is not activated when there's not power coming here that this side is closed so in other words Power is coming in the 30 and flowing through to 87a so there's no power coming through to 87. now if you're on a four pin that just means that there's no power going to 87 yet now when this is energized so when there's power coming to this then that means that this circuit closes and now we've got power going to 87 so on a five pin it means okay it went from 87a 287 when this was powered and again we'll show you this here in one moment and so that means now 87a is not powered well where would you use this well you could do things like uh under normal just key on uh maybe your electric cooling fan is running and maybe you have two fans or maybe you have a low high speed and then once the AC trips on maybe it sends power to this relay then calls it over to 87 and kicks it into high or kicks the second one in so that's where you could use the 87a and the 87. otherwise it could just be your lights and once you turn the light switch on then it calls us on and again rather than running out you know a a brand new wire which this works in really well for say your muscle cars things like that that didn't have big wiring going to those old incandescent bulbs but now you want to throw a Xenon or an LED a high-powered LED well those draw some amperage and so you don't want to be running that through the switch all that high power flowing through that old switch and you could run that lower wire that smaller wire to the relay and then run you a new wire from the relay to the headlight so let's actually test this procedure here with one of these relays let me grab this one here since it's got larger blades on it's just easier to figure out and while I'm doing that let me just show you here most of your relays in addition to having the little schematic there on the side or on the top it also has the numbers on the blades because the number or the the blades don't coincide with the positions that you see here by the way and let's see if I can get this to show up here little silver here might stand that out a little bit now I'm wasting my time now that didn't show up here's a better one so that one kind of showed but you can see the numbers actually show up on each one of the blades so you're not in the blind when you're doing this even though you could figure it out as well with your multimeter so I'm going to turn my multimeter on and this one's pretty cool because I don't actually have to switch it it actually senses between uh between ohms and voltage and DC and ac voltage and as well as continuity so it kind of is smart in a way and the first thing I could do is check resistance across 85 and 86. so I want to find 85 is here 86 is here and again it doesn't matter which lead is on where and you will see I get 85 ohms of resistance now most of these should run somewhere between 75 and 100 you might get a little over that but typically most of the ones I test are between 75 and 85 or 75 and 90 something like that and that should be kind of a normal resistance across the switch side of the relay now also what you can check here I can check across 30. remember 30 I said as the power coming in and normally closed is 87a which means the power is typically without any power going to it the power is coming into 30 and out to 87a so I could find 87a which is in the middle and I can check across 30 and I should have get the beep sound there we go so we've got continuity across that so we've got a closed connection this wire is actually flowing from 30 all the way through to 87 now and I should not get that on 80 or on 87 I should get it on 87a and not on 87. so there I've got an open circuit it's not recognizing anything which is correct so again across 85 and 86 I'm getting my 75 to 90 or 75 to 100 I'm getting 85 ohms across 35 to 87 a I get a closed circuit and 80 and 30 to 87 I'm getting nothing an open circuit which is the case now when I power this I should see it jump from 30 to 87 and not be closed on 87a this should be open so the switch should flip over here and power should be going to there so I'll take my little battery here and I'm going to send power 285 and then I should be able to hear this click when I touch 86. I held that up to my mic so you should hear that so it's clicking so I know it's working per se but let's check that so now we've got that we we checked it without power going to it right we had power going from 37 to 87a now we should have an open circuit on 30 to 87a and we do we've got an open circuit now and now we should get continuity so now we switch from going to 87a and now 30 is flowing through to 87. so now we know the relay is working in its idle situation where now we could power through from 30 to 87a and we also know that when we get power and ground to the relay that now it's working from 30 to 87. now real quick on a four prong as I was mentioning only thing we're not going to have here is 87a so basically we should be able to test resistance across it if we do we're getting 78 so we're getting seven to eight ohms of resistance 82 80. so 80ish ohms of resistance across the switch side of the relay which is correct so under its normal State we should have no continuity here with the relay now if we power the relay should hear it click we hear it click now we should have continuity across these two and there we have it so now it's in a closed state without this we're an open state and again one more time now we should be in a closed State again there we go so we've got continuity again so four prong all we're doing is eliminated 87 . see they're powered up or powered down it's not switching between uh two different components I've got a cool little board hooked up here that should be able to kind of show us how we can control uh two different things with one of these relays so what I'm going to do here I'm going to put this relay here in the middle okay so here's what I've got going on if you can kind of see my my mess here is I have power going to the relay on the switch side on 85 and 86 or 86 and then I have power going to 30 as well simulating that that would be our power waiting to go out and you see and it's switch state right now because actually I have power going to it then we've got the light coming on now when I turn power off going to the switch it's going to return back to the 87a state and it's going to power something different so watch this when I take power off of the resistor side of the relay so right here I'm going to take power off the resistor side now the light turns off and the window motor came on turn that back on and now we got power to the relay and it's powering the LED and now it's the window motor so in this case where there's power going to it it's running something and when there's not power going to it it's returning back to its restful State and then powering in this case the window motor I know that doesn't make sense of why you'd run a window motor but you get the fact that it could run one thing until it calls something else on or it could run a high low something like that as well and now let's just quickly open one of these up and pretty simple what's going on here so again I'll go to 85 and 86 and we'll look and see the coil and then once it's energized you'll see that Gap closed right there so once I energize this you'll see the little Gap closed it looks almost looks like points so that's all that's happening when we energize that relay is that's closing that circuit or switching the circuit from 87 87a or just turning 87 on hey by the way I highly recommend you should already have a multimeter if you're working on vehicles and they're cheap to buy you can buy these things pretty cheap you know whether you're kind of buying a more conventional style or like this one here that's kind of almost like a fold and kind of does a lot of automated stuff whatever just make sure you have a multimeter as well as these wire leads as I mentioned like six bucks for this 10 pack uh 12 bucks for these longer leads that are also carry like 10 amps so highly recommend those things we'll have links in the descriptions or you can find them on your own but they're cheap to buy and they're very well worth it well really when you break this thing down it's really not that difficult to understand now every time I have to kind of think for a second to remember all the things that I used to know you know the month prior before digging into relays again but really and truly it all makes sense on these whether it's a four or five prong relay it doesn't matter you got to figure it out that either you know 87a is naturally powered and then when the switch comes on it switches to 87 and you understand how the process access all works and once you understand this it makes it a lot easier especially when you're building those Resto mods or you know restoring those old cars and putting updated Electronics in them and not have to rewire the entire car because now you can use relays and you don't blow fuses anymore and you don't burn up old wiring you can use relays and circumvent a lot of that and power them the right way and you don't have that voltage drop like you would if you're using that old wiring now how do you fix it if you realize man it's not my relay that's bad well that's a great question well we know that 85 and 86 on here are the low side or control side control side is a better word better term the switch side the coil side of the relay we know we need a power a 12 volt power source and we need a ground now as I mentioned be careful because it may not be the power side that switched it may be the ground side many ecu's or CPUs the computer and the vehicles like to control that ground side as well or just the ground sided not the power side so just because you have power don't necessarily mean that you have ground as well so make sure do some continuity tests and test from the the ground on that side to the to the ground on the car to something grounding on the car until if you have ground or not and then maybe key it on and see if maybe that ground comes on but anyway now you know that hey if I've got you know 86 is my power side check do you have 12 volts coming to that when that switch is on or when that key is on check do I have ground on the on the 85 side or the 86 side make sure you've got grounded positive on one of those and then okay do I have power coming to 30 so we know whatever prong wherever the pro wherever the number 30 prong is fitting in I should have power going to that when that switch is on or when the whatever's powering that should be providing that 12 volts of power to that number 30 slot and then do I have continuity from 87 or 87a to what whatever I'm powering so now you can understand that you can really diagnose and really you can eliminate all the good things leaving you with only the bad things and you're really shrieking down that opportunity of what can be bad in there and help you actually diagnose what's going on with your wiring hope this helps you let us know in the comments what you think also follow us on Instagram Facebook Twitter and even Tick Tock and if you don't mind would you 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Channel: Shop Tool Reviews

Views: 530,612

Keywords: how to diagnose relays, how to wiring, how to fix relays, is my relay bad, diagnose relays, troubleshoot relays, shop tool reviews

Id: S-DwV0HLsE4

Length: 21min 29sec (1289 seconds)

Published: Fri Sep 23 2022