Summary

Relays are everywhere in your wiring loom, but few people really understand how they work. Learn pin configuration, high/low side switching, and flyback protection — done right.

00:00 Hey everyone, welcome to today's webinar.
00:02 I'm Caleb here at High Performance Academy.
00:04 It's great to have you along with us.
00:06 Today we're going to be looking at relays, a pretty common component in our electrical systems these days.
00:13 Most of the time, you know, with motorsports and our performance wiring, we do tend to hear PDM this, PDM that, you know, why don't you use a PDM module.
00:21 But relays are still very relevant, they're a very handy component and of course in all of our cars that we have today, especially if we're driving 90s, 80s, 2000s cars.
00:31 So, I'm going to go over today, you know, just the basic principles of a relay, why we even have them, how they work and just some ways you can diagnose a faulty relay or hook one up yourself.
00:44 If you're watching live with us today, I really appreciate it, but this is a recorded webinar, so, if you need to get away or you need to watch at a later time, that is completely okay.
00:53 We will send it out to you via email and it will be on our archive for you to watch at any point in time or to go back on.
01:01 If you're sticking around though, it'd be great because at the end we're going to have a Q&A where you can ask some questions and I will try and answer them to the best of my ability.
01:12 If I just hold off until the end for the questions, I'll give you a prompt as we go when we get a bit closer, just in case I answer something a bit naturally through the process as we go.
01:23 So relays, what are they? Essentially a relay is an electronic switch, electromechanical switch.
01:29 It's much the same with just a general mechanical switch.
01:32 We need to input some sort of input from ourselves, be it physically, you know, flicking a switch to actually, join contacts and create a connection.
01:41 A relay does the same thing, but it does it electrically.
01:45 It uses an electromagnetic force to pull contacts closed or move a lever and close contacts or open contacts and generally do what a switch does.
01:56 Now, there are caveats to this, there's different kinds of relays like flasher relays, there's latching and timer relays that all have a different purpose, but fundamentally they are very similar or the same and have the same sort of internal working principles.
02:10 So, that's mainly what I'm going to concentrate on today and go through them.
02:14 So, on the bench here I've got, if we look at the top down, a few different types of relays, well actually they're not different types, they're just different form factors or packages.
02:24 So, while relays are all very common in how they work, they do come in a variety of sizes and pinouts and just configurations.
02:32 The most common that we sort of find in automotive is our four or five pin relay, which is this one over here.
02:38 This one's got an internal fuse, most of the ones you find won't have an internal fuse, it's just what I had lying around.
02:46 This is the most common that you'll find but also the ISO 180s, that's just a different sort of pin layout and form factor, but they are essentially the same relay here, the four pin over here and four pin there.
02:59 The ones I have in the center here, these are all OEM relays from cars that are laying around the workshop and I was able to pull them out.
03:07 These two from my Caldina specifically, I need to make sure I put them back in before I leave.
03:13 So, they're all fundamentally working the same way, so how is that? What are they actually doing inside? I'll just draw a bit of a quick diagram here.
03:22 So, in our standard four pin relay, we'll have essentially two sides of our relay, a control side and a main contact or circuit side, switch side.
03:30 And on our main side we have a coil and if I just draw two really quick pins and then we're going to go like this, that's my coil and there'll generally be like an iron core or something in between inside of that coil.
03:44 If you've watched some of my other webinars, we often talk about electromagnetism and how passing a current through a wire will create an electromagnetic field around that wire.
03:56 If we wrap that wire into a coil, that then increases the strength of that magnetic field and we can then use that to successfully move things or attract another part or component.
04:08 So, in the case of a relay, we have our coil here which will be generally rated to a 12 volt rating.
04:14 They can be rated differently to what the switching side is, but just to keep things simple we'll keep everything 12 volt.
04:22 So, this will have just a 12 volt input and output, 12 volt power and ground.
04:26 So, I'll just put that here.
04:28 With any relay, it doesn't actually matter which way they go unless it is a diode protected relay, but we'll get into that a bit later.
04:36 And, so when we pass current through this control circuit, we are going to move our switch which is our second part of our circuit.
04:44 And that'll usually inside look like, I'll have kind of a pole in the middle and you'll have, how am I going to draw this, a plunger on top.
04:59 And that's one side of our switch and then the other side of our switch will generally be connected to the mechanism of our relay.
05:06 So, say we have a 12 volt coming into here, that's what we want to switch.
05:10 We want it to switch over to this side, that's going to go to a fan.
05:14 And the way it works, we put power through our coil, magnetizes, pulls this lever shut, that then contacts this pin here and we create a circuit.
05:24 We join our circuit together.
05:26 And very simply that is the principle of our relay, how it works from using one circuit to switch another circuit.
05:33 So, why would we actually want to do that in the first place? Now, with electrical, one of our big issues is passing current through wires creates heat, we get voltage drop and the more current we pass through, the more that increases.
05:47 So, when it comes to things that generally, draw quite a bit of current, things like fans or fuel pumps, we don't really want to be running wire all the way from the power source, the battery, into our cab to a switch and from that switch then to our component being a fan at the front of the car all the way at the back for a fuel pump.
06:07 Passing a high current through that wire at such a long distance will create a substantial current drop and it can also create quite a bit of heat from those wires and even the components.
06:18 So that's one side of it that is a bit of an issue, but also passing that current in general, our switches aren't really rated to the current of say a thermo fan or a fuel pump.
06:28 You can get specific switches that are rated to higher currents, but they generally are bulky and sort of industrial, your big toggle switches and when you're trying to build a nice dash or a nice display or something you don't really want those big bulky switches.
06:45 So, you can't really run that kind of current through that switch.
06:48 So, that's where a relay really comes into play.
06:51 We don't need to pass a lot of current through our coil to get it to work.
06:56 It's in the milliamps and we don't need really thick wire, we can run 20 to 20 gauge wire to our relay coil and sufficiently switch that over a long distance as well.
07:05 We'll have minimal voltage drop because of the low current and we can place our relay very close to our power source and keep our main power wires very short.
07:15 So, we'll have a very small switch, I've got one over here actually, it's an auto switch, they're rated only to milliamps.
07:23 So, if I tried to pass the current through it of a fuel pump or a thermo fan it would most certainly burn out the contacts and be useless after that.
07:32 So ideally, well always in an automotive world, I would hook that up to a relay through my coil to switch the coil using just that switch and then that with the electromagnetism will close our contacts and close our circuit for whatever high current we're passing.
07:48 Now, it's not only that we can use relays specifically for just controlling a circuit in a certain way, we have different type of relays like I said before, timer relays, latching relays, flasher relays that can actually serve a purpose.
08:02 They have a bit of a different internal makeup and function slightly different.
08:07 The main ones I'm going to sort of focus on are these switching circuits, there are a few different orientations and to show you that I've got a this relay here that I've got in the middle is from a Porsche and it's actually, if you put it into this area over here you should be able to see, might be a little bit blurry.
08:25 We've actually, got two coils in this one and this relay setup is two relays in one essentially.
08:32 Just to quickly go over the anatomy of a relay, the general how most of them look.
08:37 They will be this sort of boxy sort of style, they'll have their pins generally on one side of them usually at the pinout or a wiring diagram of how the internals work.
08:47 Some of them do not, especially these smaller ones, they just simply have their part number on, but if you were to google that part number or go to the manufacturer you will get a data sheet that will tell you how it's wired up.
09:01 Underneath on our pins we do have pinout numbers, if I turn this Porsche one up I've written, it's embossed into the plastic, so it's a bit hard to see, but I've actually written on there just to hopefully try make it a bit clearer.
09:15 But all your relays should have some sort of identification.
09:18 I'm just checking this Toyota one now because I'm not 100% sure, but yeah that's even got the embossed numbers underneath it.
09:26 So, that will refer to something on our diagram and generally I'll erase this and actually draw one of the diagrams because it's going to be way too hard to see on camera.
09:39 Generally, you will see a relay drawn in a schematic similar to this and the diagram on the actual relay itself will be quite similar too, so I might actually just copy one of these, so it's exactly the same.
09:52 But we'll have a coil in the center which will be any kind of drawing, usually it's just a square with a line through it.
10:00 We'll have our two wires coming off which signify our control wires for the coil.
10:04 On top of that it will show some sort of plunger, a switch in the resting position, so some relays will be closed when they're resting or they might be open when resting, so that's an important thing to look at.
10:16 But the diagram should generally show you how that is at resting.
10:20 So, this one here it's open and not passing power through.
10:24 So, that is essentially what you'll find, some sort of diagram like that.
10:28 Different manufacturers, different companies will do it sort of differently.
10:32 And more often than not, this is another one of those cases where some manufacturers do it differently, they will be numbered fairly similar.
10:42 We'll have on our coil an 86 pin and an 85 pin.
10:46 And then for our control side we'll have a 30 pin and an 87.
10:51 As I said this can vary sometimes, it can be a little bit different.
10:58 I think these the ISO ones have, nope they have the exact same numbers on them.
11:04 What's a good example here? This, the Porsche one.
11:07 So, this one simply just got numbered 1, 2, 3, 4, 8 and 9 because that's how we count.
11:12 And yeah it's just a reference to your schematic, so you can follow along and know exactly how your relay is going to power up.
11:21 So, similar to the quick little diagram I showed you before, we power up our coil here by putting power and ground to respective sides.
11:30 That will then magnetize our plunger and pull that contact down, closing our switch and passing our current through.
11:37 So, as I said before there are a couple of different types and different arrangements.
11:42 Particularly what you'll find, especially these style that are the 4 to 5 pin, you can get a 5 pin which simply has a extra 87 pin, generally called 87A.
11:54 It's just joined to the exact same output and it's just a second pin for passing that current through.
12:02 But the more commonly found is a changeover relay and basically, that was kind of pointless drawing that, what's the best way to do this? Yep, so that 87A will actually be joined to our resting closed circuit.
12:19 So, at resting, this 87A pin is connected to our 30 supply pin.
12:24 When our coil is energized and our relay is turned on, our contact will close over to the 87 pin and change over to that other pin.
12:32 This is helpful in a number of ways.
12:35 We might have a system that needs to be on at a certain point or at resting, but if then something else happens we need to switch it over to another circuit or even just switching a circuit off in general.
12:49 Probably the two most common you'll have are those 5 pin changeover or standard relays.
12:55 They generally are referred to as single throw single position or single throw double position.
13:01 That just refers to how many different positions it can change its state and how many pins it has output.
13:08 So, a single position and a dual position.
13:12 Just as I said before, the standard relay will just have the one output pin, single position, changeover relay, two positions, dual position.
13:21 They're the most basic ones that we have.
13:24 I won't get into timer relays and latching and that type of thing.
13:28 They're just generally, a different setup of their contacts and often, especially the older ones, they'll have resistors and capacitors that help do timing functions or flashing.
13:39 These days with solid state relays it's all done electronically.
13:43 Just to touch on that, a solid state relay is doing pretty much the same thing, but without these moving components.
13:51 It does it all electronically.
13:53 I won't get too into solid state at the moment.
13:56 If you guys got questions about it at the end, feel free to ask them.
14:01 So, looking at this basic layout here and my Porsche relay that I have, we can actually point out these different parts.
14:08 If we get a nice close-up as close as we can, it might be a little bit blurry.
14:13 But these big brown sections here are our coils.
14:16 So, that's our wraps of small copper wire.
14:19 They wrap around hundreds of times and create our coil.
14:23 We have our main frame which is essentially holding everything together, but also serves as a main contact, generally our main power in.
14:31 And that is connected to this lever at the top here which is also on the other side of this relay.
14:37 They generally are connected to some sort of spring to hold them in an open position and they will be connected to a strap just to make sure they have good electrical connectivity.
14:49 And that will go to a set of contacts which are on the side here and depending on the type of relay it is, it'll either be one contact that is just connected to a pin output or two contacts where it'll be resting on one and the other will be the switching for a changeover.
15:06 And looking at my diagram that I've got here on my case for this, they are just two standard relays, but the way it works is one feeds power into the other.
15:18 From memory this is a, I think it's the fuel pump circuit for a Porsche.
15:24 So, it has separate ways of working that depending on whether the ignition's on or the car is stalled or cuts out, it will cut your fuel pump off.
15:34 Obviously, these days with solar state relays, PDMs, it's a lot easier to program different types, but back in the days of relays, and we're still in the days relays, all this kind of circuitry was done by different configurations of things like relays and yeah those kinds of circuits.
15:51 So, actually I've got a power supply here.
15:53 I will hook it up and we can actually see what happens.
15:57 The most obvious thing when we're working with relays that we notice is the identifiable click that they make.
16:03 Because they're a mechanical relay, that plunger and the contact moving side to side does create an audible noise.
16:12 Now, I'm just going to remember what pins are what here.
16:16 So, I'm just going to hook this up to my power supply without touching them together and my switch.
16:23 Now, if we get in nice and close there, what we should actually see is the plunger on, I'm pretty sure I connected up to that side of the relay or this coil of the button.
16:36 So, there we go, hopefully you guys can see that.
16:39 All I've done is powered up our coil, we've created a magnetic field and pulled that contact closed and is now powering up that circuit which on my relay looks like it is pin four and pin two.
16:53 So, with that I can actually power up something like a light.
16:57 Now, this is an LED light, I probably could power it off this switch successfully.
17:02 But for something like say you're hooking up driving lights or an electric fan, the ideal way we want to do that is through a relay.
17:12 So, we're not passing that high current through our dashboard into small switches and causing long wiring lengths that can cause current draw.
17:21 So, I'm just going to work out how I can do this nice and easily.
17:25 Let's hook up what I want, four and two.
17:28 So, we just want to pass current through it.
17:31 I need earth on one side which I'm going to hook up here and we are going to pass power through there.
17:38 So, I need earth on my contact as well.
17:41 I probably didn't think this through completely, it's going to be a little bit difficult to get everything in one place.
17:49 Actually, I did think this through, I brought the probes here, that makes more sense.
17:58 Okay, so earth, hopefully, I can do this without being too messy, and my power.
18:10 So, power is going to come out of my pin four, either pin four or two, doesn't actually matter which side you are switching a circuit through.
18:21 There are certain situations with, if you're wiring up power windows or central locking actuators, you can use two changer relays in essentially a reverse function and it allows you to kind of like a h-bridge setup where it'll put power on earth and then swap it over, which if we get time I might show you a bit later.
18:41 Let me just hurry up and get this hooked up.
18:44 I keep distracting myself, I want pin two.
18:46 Good thing I've labeled these.
18:50 Pin two, that's my output, and I'm going to power up, where am I? I had this before, pin nine.
19:03 We want power going into our relay, which was pin four.
19:12 So, now I've got power essentially going into the relay, not coming out.
19:16 I dropped one of my cables and then all I need is, I need to bridge ground to my coil.
19:30 And where's my ground? There it is.
19:33 Now, have I done this correctly? Hey, I have.
19:35 Cool, so what's happening here? I'm simply connecting up my coil with power and ground through my switch, closing contacts, that is then passing the 12 volt through our contacts there, successfully to our light.
19:50 So, in a less messy motorsport environment, any kind of car, that is going to allow us to switch a high current or even a low current with a very small switch or small component.
20:02 This also comes really in handy for things like thermo fans, if we want to automate them.
20:08 We can replace that switch with any kind of switch or component that can turn a coil relay on.
20:13 So, something like a thermo switch, a thermal switch in the radiator or coolant system that will close at a certain temperature, that will then close the contacts, switch on our relay and switch on our fan and allow us to control a fan without any personal input or user input, and it will turn on at the exact temperature we want and turn off at a temperature.
20:37 Also the other most common way of doing this, and probably more something that you guys will come into contact with, is powering up a relay with an ECU.
20:47 A lot of ECU outputs are much like my tiny switch here, that can't pass a lot of current through them.
20:53 They're able to switch something on and off via ground, but they can't directly switch say a thermo fan or even you know a very large light, anything that's going to draw any sort of considerable amount of current.
21:07 I think most ECUs are rated to say 200 milliamps.
21:10 So, that's where we use a relay with an ECU.
21:13 We can use our ECU to essentially program any kind of parameter, whether it be from RPM, our coolant temp or oil temperature, anything like that.
21:23 That ECU will then switch our coil contact, it would only draw very little amperage through our ECU, but it'll be able to switch a much higher amperage through the main contacts to whatever component.
21:36 Now, touching on that, the control side, as I said earlier, we can power it up either way.
21:41 Conventionally when we refer to relays we try and stick to 86 being our positive side and 85 being our ground side.
21:48 With most standard relays this isn't an issue, it can go either way.
21:52 You can get relays that are protected with a diode, I'll get into that a bit later, but that diode will essentially make it polarity sensitive and more often than not it will be in that 86 positive 85 negative orientation.
22:06 So, if we just kind of stick to that we are less likely to get caught out by one of those diode relays.
22:13 But we can also switch either side.
22:15 So, we can switch positive, we can switch negative.
22:19 With our ECUs generally they do switch only a negative side, so we would supply power to our coil from one side, generally with say an ignition or sometimes a constant 12 volt source, and then our 85 ground side will be switched by ECU.
22:34 So, that is another advantage of relays, we can switch much higher current with very sensitive or amperage sensitive components like an ECU.
22:44 Things like PDMs, they're designed purely for controlling that high current.
22:48 If you were to try and integrate that into an ECU it does raise the cost quite considerably because they need much stronger components that can withstand that high amperage.
22:59 So, that's why generally you'll find ECUs out there that are combined with PDMs, they are more expensive than other components separately.
23:07 So, going on that we've sort of looked at the basic layout of a relay, some of the different pinouts.
23:14 I will quickly mention the different pinout styles we have.
23:18 You really need to look at the diagram of your particular relays because they do vary quite a lot.
23:25 Both of my Toyota ones that I have here don't have any kind of reference diagram on the relay itself, but it is something that I can get from a wiring diagram or even searching the part number sometimes you can find it.
23:41 This one here is from our C5 Corvette and again it's a standard, this is a change over relay actually, sorry.
23:49 So, this has got my, it's the same pinout as what I've got here, 85, 86 for our coil, 30 for our input, 87 for our closed and 87A for our, oh sorry, 87 is our open, it's open at resting, 87A closed.
24:03 So, I can actually, I'll show you how that functions as a changeover relay, what it sort of does.
24:10 If I can get this unclipped nice and easily, let's put that out of the way.
24:17 So, much the same, we just want to put our switching circuit across our coil which on here is as I said 85, 86.
24:25 I'm going to double check, that is 86 there and I simply need one of these ground wires, that is my 85 over this side.
24:34 My light or my output, I'm just going to leave that off for now so, I can demonstrate the changeover function.
24:42 So, right now as that sits, if I place my wire for my light on this center pin, 87A, we can see it turns on and that's because it is in this closed at resting or normally closed position.
24:55 If I power up our coil, it's going to move that contact over and turn our light off.
25:02 If I swap over to my other contact here, as we imagine at resting, it's off, on, turns on.
25:08 So, as I said this can play a role in several different situations, but that is just, they're the two sort of most common relays that we will have that changeover or just a standard single switching maybe with two outputs or a single output.
25:26 Now, I did mention diodes, it's a protection for our coils in our relays.
25:31 So, another webinar that I have is on inductors and the what's the easiest way of explaining, the flyback voltage, the emf voltage that happens when a coil collapses.
25:44 Without getting too in-depth into it, when we power up the coil and make that magnetic field, we're storing quite a lot of energy in that magnetic field.
25:54 When we switch our contact off, turn our relay off, that magnetic field, the energy basically has to go somewhere, it collapses and that energy is put back into our wires.
26:05 So, it will go back into basically any wire that is around it.
26:09 As you pass magnetic field over a conductor it induces a voltage.
26:13 So, our two wires here that are connected to say a switch or an ECU, that voltage will go onto those wires and go backwards the way it came.
26:22 And this can happen at hundreds to thousands of volts, it's not controlled it simply just wants to put that energy into the wire and that high voltage, those spikes can be quite dangerous to electronics, particularly things like ECUs.
26:38 Back in the day with just standard switching of relays with a switch or say your lights, we don't really need to worry about it too much because that back emf, that back voltage isn't going to destroy our mechanical switches or that kind of thing, it'll get soaked up by batteries and dissipated as heat.
26:57 But for something like an ECU where its outputs and the transistors inside can be very susceptible to that high voltage, we need some sort of way of getting rid of that back emf.
27:09 And the way that is done, draw it in red, we essentially have a diode that is internal, so let's just get rid of this line because it is actually inside the relay, and it'll essentially bridge our control wires together.
27:23 Now, this is obviously not good in a normal situation, but as I said it is a diode which the conventional way of drawing a diode like that, we have our blocker on our positive side and, so it doesn't, in our normal condition as I said when we wire up one of these diode protected relays, we always need to make sure that 86 is our positive and 85 is our negative.
27:46 Most of them are wired up in a way that if you were to reverse it, it won't actually function.
27:52 So, by doing this we've got our normal connection here, we can normally power up our coil, but when we get that back emf and the voltage is trying to go the opposite way, it now has a path where it can go back onto that wire, creates a circuit and it's essentially dissipated in heat and just throughout the rest of the circuit without directly going through our ECU and damaging it.
28:16 And there's lots of different components that can be damaged by that sort of thing as well, so it's not just ECUs.
28:22 The diodes are there for protection, they are called a flyback diode for that reason.
28:26 We do have other options as well, some relays will use a resistor, that Porsche one is actually there, it's got a couple of resistors on the diagram and I can see them on the little circuit board, a bit hard to see, I don't think I'll be able to even show you there, actually they're under the coil, so you won't be able to see that.
28:46 They're there for the same purpose, to give that back emf a path.
28:50 So, what else have we got here? I've gone over the basic principle of the relay and different types, let me just go through my notes quickly and have a drink just to make sure I haven't forgotten anything critical.
29:03 Probably another really good point, when I said that we've got our two separate sides, we've got our coil and then our switching side.
29:12 Because they are separate, they are generally, the way they're constructed, they're actually electronically separated as well, so they're isolated from each other.
29:22 So, in a lot of cases, particularly in control components, things like I've seen a lot in alarm systems for switching on or switching our central door locks and that type of thing, they'll actually have a relay on board that the control side is, the coil is for 5V, so it's controlled by the 5V of our ECU or control component, but it still allows 12V to go through our coil, sorry not our coil, our contacts and switching side.
29:50 The switching side is essentially just a straight contact, there's no real electronics there in our standard relay, so, any kind of, most of them are rated to any kind of voltage.
30:02 I'll look on this one in particular, nope that one doesn't give me anything, a lot of them are even rated to in the hundreds of volts, particularly for things like household voltage.
30:12 A lot of the relays that you find in household voltage in control equipment for industrial situations, they are a relay that is, the coil is rated for say 24V, 12V, 5V, but the contact sides are actually controlling the 110-240V of an AC system.
30:31 So, that is another really big advantage of using a relay, you can use essentially two separate voltage systems or control systems to switch a completely different system in itself.
30:42 These days with PDMs and ECUs we have other ways of doing that with transistors which are the same sort of thing, just electronically, that's also where solar state relays come into play, it's the same idea, less moving parts, less things to go wrong.
30:55 With relays, because you have those contacts that are closing and opening all the time, you will often, particularly with high amperage situations, you'll get arcing on those contacts, they'll get dirty over time, those contacts can't even weld together if you put too much current through them, even just over time they wear, the springs can wear, and it's all mechanical stuff that can eventually go wrong.
31:20 With that I think we'll start putting your questions in, I'll just cover a couple more things, but I reckon by now hopefully you guys have got some questions to put in there.
31:32 Let me just quickly go over a couple of bits.
31:35 Yep, I've gone over all that.
31:36 So, when it comes to actually diagnosing a relay, one of the particular advantages with a relay is, as we showed before, and you get that very audible click, like you can hear that, you hear it all the time in your car, turn the ignition on, you'll hear relays click, you turn your lights on, or a main one that you always hear is your indicator, turn the indicator on, you'll hear that mechanical click every time it opens and closes.
32:03 A flasher relay works a little bit differently depending on the system it is, there's electronic controlled ones, very old ones, they are thermal controlled, they just have essentially a bimetallic strip that bends when it gets a certain amount of heat through it, pass a current through, slowly heats up, opens up, cools down, closes, heats up, opens, closes, flash, flash, you get the idea.
32:25 These days they're electronically controlled and that sort of thing and often in newer cars the clicking that you hear is actually created by the car to mimic that clicking of a relay.
32:35 So, that is sort of the first dead giveaway of a relay if it's not working or if your light doesn't come on and you're not hearing a click then more than often than not it's an issue on your control side or the actual relay itself.
32:49 So, if you're not hearing the click you can straight away go to your relay and go okay am I getting my power and ground across my coils, if I am then you can pretty much just say that that relay is faulty.
33:01 The other advantage of relays because of the holders that you can use, which I haven't actually showed yet, but I will in a second, they're very easy to swap out.
33:10 If most cars have multiple relays you can chop and change and swap relays over.
33:15 Be a bit careful with that, make sure you've got the right, pin out on them and everything, but it is quite quick and easy to diagnose with a separate relay whether that relay is faulty or not.
33:26 But also you can get situations where that relay is making a click.
33:30 In that sort of situation you hear the click, your next instinct would be to go to your switching side.
33:36 If you're hearing a click then your coil is functioning as it should, it's drawing that contact over.
33:41 So, go to your switching side, check for a ground or power depending on what is being switched on either side and whether it's passing through.
33:49 If you've got that power going in and then on the switch side and you're hearing a click, but there's nothing coming out, again probably a relay issue, swap a relay out and yeah that should lead you in the right, direction.
34:02 I do often find that with those kind of situations relays they're very rarely the actual issue.
34:08 While they do deteriorate over time they are fairly reliable.
34:11 With that some out of the packet brand new ones can be faulty, but again it is quite rare.
34:16 But it is a really good diagnostic tool in itself, just that click and having all your pins in an area that you can quickly diagnose.
34:24 And with that I will show you a couple of holders that you can get.
34:28 So, when it comes to you know mounting these relays you can't just plug them into your wires.
34:33 You can put just general crimp terminals on them, your spades, and plug them in.
34:38 That doesn't really solve the fact of mounting them anywhere, that type of thing.
34:42 In your OEM situation you will have big relay blocks with fuses and all that kind of stuff.
34:47 You can buy smaller ones and aftermarket relay blocks and generally, they call them power distribution units, they're not a PDM as such, but they do distribute power in certain ways.
34:59 But more often not than you'll find in singular cases like this you'll have just relay blocks as we call them.
35:05 It's just a singular plastic block.
35:07 These have really simple brass spade terminals.
35:10 They go in really nice and easy and they click in and once you've got that pinned out that's ready to just receive one of the corresponding relays.
35:18 Because these are the most sort of common relays you'll find in your day-to-day automotive.
35:23 These are generally, the more common relay bases.
35:26 That then just plugs in and is easily adaptable to our wiring environment.
35:30 This one that I've got over here is a weatherproof one.
35:33 They come pre-wired just to make them weatherproof.
35:36 They have these seals.
35:37 I think you can get them in a non-pre -wired as well.
35:40 This one is for a particular relay that has a kind of a skirt on it that then plugs on and makes it truly waterproof.
35:46 But a conventional four or five pin relay will plug into that as well.
35:52 So, with that as I was saying it becomes a really good diagnostic port because you've got your control side wiring here and your power side as well.
36:01 And you can really quickly and easily with a multimeter check what's happening with the situation.
36:07 And with that you do need to, I recommend getting your wiring diagrams and assessing how it is actually switched on or controlled.
36:15 Because as I said the switching side of it, the coil side, can be switched on either the ground or the power side.
36:22 You just need to have power and ground to either side to make it function.
36:27 And respectively with our switching side we can switch a positive 12 volt supply or any supply.
36:33 Or we can even switch a ground.
36:35 And that's where with our power windows and things like that we'll actually have, if I can actually draw that one here, you'll have two separate relays.
36:44 And basically, what you'll have is the 30 becomes your output to your motor.
36:49 You have another relay which is going along with it.
36:54 Your coils will be controlled as you're up and down.
36:57 So, one relay will be up, one relay will be down.
37:01 And essentially our 87As will have constant ground to them.
37:05 So, we'll have two relays.
37:07 I'll just draw the other one quite quickly in an opposite kind of fashion.
37:12 Drawing upside down.
37:13 And then our switch.
37:15 I'm still drawing on the board here.
37:21 So, our ground will actually go to both sides of our relays and then to our motor.
37:28 And what we have here, basically our motor has ground on both pins.
37:33 When we turn on one of these relays the opposite side, or sorry the 87 pin will be hooked up to power.
37:40 Let's do a 12 volt here just, so we know that's hooked up to power.
37:44 So, what will happen, this is up, this is down.
37:49 When we press our up button this coil energizes, swaps over from our top contact to our bottom contact and puts 12 volt power on that side.
37:57 And we've still got the ground on here on our resting contact.
38:01 So, that allows 12 volt one side, ground the other.
38:04 Our window will go up.
38:06 When we release that switch we'll go back to having ground both sides.
38:10 Hit our down switch, we'll then put 12 volt on this side allowing the motor to go the opposite way.
38:16 So, that's just a quick simple way that power windows can be wired up.
38:21 Same thing with central door locks.
38:23 They're similar, they need to go back and forth, so you can use relays.
38:27 And a lot of your aftermarket alarm systems, things like that, will have those on-board circuit circuit board relays that are switched in a very similar way.
38:37 I'll just have one quick look to see what we've got here and then I'll get into some questions.
38:43 So, I've talked about our diodes, polarity sensitive.
38:46 Yeah let's get into questions I think.
38:48 Hopefully, you guys have got a few there that I can get into things a bit deeper.
38:56 So question, first one we've got.
38:59 Innerspace 5, single throw.
39:02 Can we explain the throw? Is that just the single wire pins shown as 85 and 86? Yep sorry let me just go into that probably a bit deeper.
39:13 So, we've got single throw, dual pole or hang on let me just, I probably got that the wrong way to it.
39:22 I don't want to confuse everyone let's just, normally closed.
39:27 I normally just refer to them as a standard relay or a changeover, so that's why I'm just double checking here.
39:41 Single throw, dual position.
39:43 So, yeah, so the throw side of it is referring to, that's the best way to explain this, you essentially have multiple contacts in a dual throw.
39:53 I don't even have an example of that.
39:55 Basically, think of it as the two relays in one situation.
39:59 You'll be controlling two separate circuits with that one coil.
40:02 I really need a good example here of that.
40:05 It's the same with switches.
40:06 You get a dual position, dual throw, single position, dual throw, that sort of thing.
40:11 Essentially you'll have two separate circuits in a switch where you can put a separate power on two different pins and as you activate that switch it'll put, connect two separate circuits.
40:22 So, that's what it means by a dual throw.
40:24 So, a relay is the same thing.
40:26 You won't often find a dual throw relay.
40:28 Technically that Porsche one isn't a dual throw because it's two separate relays inside.
40:33 But yeah it will basically be two separate circuits and then the position, dual position, is how many outputs or how many different positions that circuit can be in.
40:43 That might have been a bit of a confusing way to explain it.
40:46 I'm going to erase this and actually try and draw it properly because it is a good question.
40:54 Let me get rid of some of this stuff as well.
41:04 So yeah, easiest way to draw this, we'll have our standard coil.
41:08 So, it's not the 85, 86 side.
41:10 We'll still have just the single 86 and 85 wire, two wires sorry, that will control our coil.
41:16 But we'll have, let's draw a plunger, we'll have two separate circuits like this.
41:21 So one will be there, one will be there.
41:24 That's my very bad switches.
41:26 And then the outputs will go like this.
41:28 So, essentially what we've got there is two separate switches inside the same relay that will both close at the same time when we activate that relay.
41:38 So, that's what it means by the dual throw.
41:40 Essentially you've got two contacts or two poles there that are throwing at the same time.
41:46 Yeah I think that's a better way to explain it.
41:49 Hopefully, that's answered the question.
41:52 If not, chuck in a bit of a follow -up.
41:54 But yeah that should explain it.
41:58 Next question, I've got two similar questions here.
42:01 Should you fuse before or after the relay? If you have a fuse on each circuit of the relay, do you use a fuse on the power supply to the relay? Yeah, so when you're adding in a fuse to any circuit, the main thing you're sort of fusing against is your wiring.
42:17 You're trying to protect your wiring from being overloaded.
42:20 So, ideally we've got main power wires coming into our relay.
42:24 We really want those main power wires being fused before the relay.
42:29 Essentially it will protect our wiring and also our relay.
42:32 So, that's relay that I showed you before, that I've now lost.
42:36 It's over here.
42:37 The fuse on that one, it's fused on the power side, so the input.
42:41 Ideally you want to put the fuse closest to the power source, so, closer to the battery, because as I said it's protecting your wiring.
42:49 So, when it's here at the relay you're not actually protecting the power supply from that relay to your battery.
42:56 A lot of the time when you're adding in these relays they're handy because you might be adding into an existing circuit that is already fused.
43:05 If it was a situation where say you were switching multiple circuits with a relay, say you had that was switching ignition which then goes to other relays as such, generally in an automotive OEM circuit you have a main sort of large fuse that can handle the current of all your circuits.
43:23 That'll protect the wiring to that relay, the main relay, and then you'll have separate smaller fuses for your smaller components.
43:30 It all depends on the wiring that's coming out as well.
43:33 If I was to split this off, if I had say a main major wire coming in that was rated at 30 amp fuse before that, if I was then bridging off at smaller wires that were only rated to say 5 amp, I would ideally want fuses after the relay at 5 amps each to protect that wiring.
43:49 Again hopefully that wasn't a too convoluted answer to that one.
43:54 It's probably actually another good thing to touch on with relays is they are rated to very different amperage ratings.
44:01 It's generally just the contact side, they are mechanical components and you put too much heat through them and they will weld together as I say, so they are rated to a different current.
44:12 This standard one here is doesn't actually say on it, but it should be, I mean it's a 30 amp fuse, you'd expect it to be rated at 30 amps and from memory it is.
44:21 This Porsche one here is only rated at 15 amps and I would say that's probably because it's two relays in one, splitting that 30 amp across two relays.
44:29 So, yeah you do want to keep in mind your amperage because there are situations where say this fuel pump relay, I wouldn't use that for a big thermo fan that's pulling 25-30 amps.
44:40 You do get much much larger ones upped into you know 100 amps, 200 amps.
44:44 You start getting into a situation where you're actually using solenoids and not relays themselves.
44:50 It does have a bit of a different setup where the plunger itself has the contacts and joins them together.
44:57 Essentially yeah, different kind of thing, same sort of process.
45:01 Hopefully, that has answered that question.
45:04 Follow-up comment to the first one, sorry I thought I might have answered that a bit terribly.
45:10 I can see in this video he is calling the primary the coil side and the high amp secondary.
45:16 It's being called the switching side over there in New Zealand.
45:19 It's one of those things that's just you know there's no actual wording for it I guess or like set wording, same sort of similar to our contact pin numbers.
45:30 We try and stick to a certain protocol I guess, but it does change sort of everywhere.
45:37 I've heard it referred to as the primary and secondary side as well.
45:43 I guess in my head I've always, because in our motorsport and just automotive with coils, you have the primary and secondary coils and that's sort of where my head goes to with primary and secondary.
45:56 But very much yeah, your primary circuit is your control, your coil, and your secondary is your coil, sorry your switching.
46:03 It all just depends on yeah, it's a wording thing, can be yeah worded however you want.
46:08 Next question, I've got frankrizzo2566.
46:12 On a high horsepower EFI car, what's the best way to prevent voltage drop or electrical noise from relays, pumps, fans, and ignition coils from affecting the ECU sensors? Yeah this is a pretty in-depth topic.
46:28 I did do a webinar on electrical noise in itself.
46:32 So, it's that whole situation where we're turning these coils on and off and that movement of the, sorry the collapse and the expanding of that magnetic field is inducing voltage into other components, particularly sensitive sensor wires that are in our harness.
46:51 Generally, the best way to prevent the voltage, and sorry you worded it here, best way to prevent voltage drop or electrical noise.
47:01 Yeah, so the electrical noise side of it, generally you know when we're wiring up a motorsport loom we'll be using shielded or twisted core wires for those sensors that are particularly vulnerable, things like your speed sensors, engine position sensors, knock sensors, that type of thing.
47:17 The other thing you can do is keep your main power side wiring that is going through our relays and things away from those circuits, just you know that magnetic field can only go a certain distance, so keeping it away entirely is another option.
47:33 But at the end of the day it is just an inherent thing, part of electrical and our automotive side.
47:39 So, yeah there's, most of the time you know I've found in my situations if you're using a good quality wire, a good quality shielded wire, whether it's twisted core or not, that will generally withstand any kind of electrical noise from those types of things.
47:55 Your bigger problems are your pumps, your fans, and your ignition coils.
47:59 I did a webinar on inductors and specifically talked about ignition coils and how much of a problem they can be.
48:06 As far as the voltage drop, well that's sort of, that's why as I said at the beginning one of the reasons we have relays is to shorten the wiring as much as possible.
48:15 Really the best ways to prevent voltage drop is to size your wire sufficiently.
48:21 If you are getting voltage drop then your wire is either too long or too small, so shortening that distance or bumping up the size is sort of the only real way that you can solve that.
48:31 You can get bad connections that will cause voltage drop, but that's sort of a whole other issue in itself that has to be rectified before you look at wire length or size.
48:42 Next question, Innerspace56 182ktfw, the secondary side of your ignition coil is a high amp blast to the spark plug, correct? Yes, so getting a little bit off topic here, but the secondary side of an ignition coil is what's essentially creating the spark in your engine.
49:03 The primary side is the switching side which is I guess sort of where the correlation comes to relays.
49:10 Our primary side is the side that we are switching on and off to switch something else.
49:15 Next question, UrbanBroccoli, normally, open versus normally closed relays, do you have a preference? I mean generally it really just comes down to your situation of what you're actually trying to do.
49:30 More often than not I very rarely see normally closed relays just because more often than not we're trying to actually switch something on.
49:40 Normally, closed comes in handy if you're trying to cut power to something, say you can use them for a safety switch for your fuel or even your engine itself, you can put one in line for your ignition that is hooked up to say an oil pressure sensor.
49:58 If the oil you lose oil pressure it switches the relay which then cuts that contact.
50:04 It's basically just the reverse way of switching something.
50:09 If it's something that has to stay on all the time, you're expecting it to stay on all the time, you don't really want that little bit of current draw from your relay or the relay can get hot.
50:18 You will notice that with your relays in your car, they get hot when they're left on for a while, perfectly normal.
50:23 There is too high, but most of the time they will be quite warm.
50:26 So, if you have a circuit that you do have on all the time and is very rarely switching off, it might be a safety situation, the normally closed can be handy for that because you're not keeping the coil magnetized and activated the whole time.
50:40 Next question, Urban Broccoli, last question from me, that's okay I appreciate all the questions and I do enjoy going through them, so don't feel like you're asking too much.
50:50 Although they don't commonly fail, what would your typical approach be when it comes to troubleshooting a potential faulty relay? So, in any kind of circuit, obviously if you can, get a wiring diagram to see how it is actually switched.
51:03 That's generally the more confusing side of things is how a relay is being controlled, whether the power side or the negative side of the coil is being triggered or what type of circuit it is actually controlling.
51:16 So, get familiar with that, what you're actually looking for.
51:19 Quite simply as I said before, listen for that click.
51:22 If you're either your relay is bad or your control circuit isn't working, if you are hearing the click, again could be a bad relay, could be welded contacts or something like that, but then that points more towards your switching side.
51:36 And as I said, very easy if you've got a nice accessible relay block, pull a relay out and just get a multimeter and check all those contacts and see you're getting what it should be.
51:47 If everything is there that it should be there, then obviously your relay is the problem.
51:52 You can also, very easy with those relay styles like this, I used to have in my toolbox just a wire with a couple of spay terminals, quite thick wire, you can actually bridge them out and check that a component is working without the relay.
52:05 And if the component is still working, then that does point you more towards the relay itself.
52:11 As far as troubleshooting, what else? It's one of those systematic things, start off with obvious things like your fuse and then start with your control side, make sure it is actually being triggered.
52:25 And then if everything there is fine, check your circuit side, make sure it's getting power or its supply and it's going to the right place.
52:35 Next question, this is a follow-up to the high amp blaster's spark.
52:42 The name was 182QKFTW, I think I said someone else's name before that.
52:50 Speaking of collapsing magnetic fields in the coil of a relay, comparing that to ignition coil, ah okay sorry, it can generate a lot of voltage, same way ignition coils do.
53:00 Yes, exactly, so that is I guess the main difference between a coil and our relay.
53:05 That back EMF and that high voltage spike in our secondary side, it's intentional in our coils, that's actually what we want to do.
53:14 That is the core principle of how a coil works, it creates that magnetic field, collapses it and induces that high voltage on our secondary side, creates our spark in our engine.
53:23 In our relay, it's not something we want, but inevitably it is something that happens and that's why we do things like diodes and resistors and flyback protection.
53:32 So yeah, they are operating in very much the same way, it's just one situation we want it, one situation we don't.
53:41 Last question I've got here, yep it is Zack is jaded, I can't speak English can I? I can never retain what wire goes where on a relay, whose idea was it to label the relay numbers that make almost no sense? Yeah it's one of those situations where whoever labeled the first relay probably didn't know what numbers were, they probably had a whole list of different relays that had all the different labels, but it's just something you gotta check beforehand.
54:11 Don't also look at a 5-pin relay like that and expect them all to be wired exactly the same.
54:16 I've been called out before, particularly I think it's like GM and Holden, they have a very similar looking relay to your standard and normal relays, but the pinout is completely different and you can quite easily fry things and screw up relays, don't ask me how I know that.
54:34 But yeah, generally with the standard relays the numbering will be quite similar.
54:39 I think we've got one more question that's just jumped in here.
54:43 What causes a relay to hold on even if the trigger side is not energized? Welding is probably the most common, so yeah the contacts can actually weld together.
54:54 You might be talking about a common situation that I find, particularly with some cheaper ECUs, so this is probably a good thing to actually quickly talk about.
55:05 When you wire up a relay, say for your fans or fuel pump or anything, try not to wire up the positive side of your coil with a constant 12 volt.
55:16 The best thing to do is to trigger it from an ignition source, basically that way when you turn your car off, turn your ignition off, that coil is no longer energized and it can't turn on by some other earth.
55:28 I say that because a lot of ECUs, particularly older ECUs or cheaper ECUs, they don't have internal protection that stops their switching contacts from going to ground, so they will actually fall to ground when everything's turned off and that'll put a ground to your coil and essentially turn it on.
55:45 And you'll find you'll most notice that with things like thermo fans, you'll turn your ignition off, take the key out and then your fan turns on even though everything's powered off or supposedly powered off, and that's generally because there is a constant power there.
56:01 And when I say cheaper and older ECUs, a lot of newer ones still do it and it's not necessarily a cheap thing, it's just I find I guess the more advanced ECUs tend to have some sort of protection against that, but I digress.
56:13 Try and stick to having an ignition source.
56:15 If it is obviously something that needs to be switched with the ignition off, then you have to have your constant 12 volt.
56:22 In that situation, you need to be careful of how the ground is switched and that whatever you're controlling it with doesn't fall to ground when it is turned off.
56:31 Okay, there's more questions keep popping up.
56:33 We're gonna, I think we're gonna stick to these being the last two because we are, yeah, we're running out of time.
56:40 I've got frankrizzo2566.
56:41 Is there a particular brand of standard relays that are trusted and durable? That's a bit of a hard one because there are so, many different brands and things.
56:49 Off the top of my head, we've always had Narva and OEX, Hella, Bosch as well have their own relays.
56:57 It's one of those, ask around other people what they generally, use.
57:01 Some people will even say those relays like Narva and OEX aren't reliable, but I mean, I've been using those relays for many, many years.
57:08 And while it is a case, sometimes you do have one out of the packet that doesn't work, it is really, really rare.
57:15 I many, many years ago was building emergency vehicles from scratch and they were chock full of brand new relays and we generally, used Narva.
57:23 And yeah, I very, very rarely had an issue with those.
57:26 With that sort of question, my sort of best advice is ask people around you in the same industry, see what they have used over time and jump in our forums as well and chuck the question in there.
57:38 All right, last question because my throat is going to go out otherwise.
57:42 Urban Broccoli, could you give an example of where you personally might spend the extra money on a solid state relay compared to a standard one? So, with standard solid state relays, the advantages of those mainly it's because you can pulse them really, really quick.
57:57 So, because there's no mechanical contacts, you can turn them on and off very, very, very fast, like in the milliseconds, to control the voltage to a circuit, things like fuel pumps and fans, you can speed control that way.
58:11 That is generally the main reason you'd go to a solid state relay.
58:15 If you're looking to speed control a motor or some sort of circuit like that, you can't do that necessarily with a relay because those contacts need time to move back and forth and every time they do that they will arc slightly, excuse me, and wear out over time.
58:31 With that, that is probably another diagnostic thing.
58:35 If you're getting low voltage to your relays, they can still switch on, but often if you're getting quite a bit of voltage drop or your battery's flat, you'll get a situation where you essentially hear that, like you hear relays flickering and that type of thing.
58:50 That's a pretty definite signifier that you've got low voltage somewhere, either a flat battery or there's severe voltage drop to your relay.
58:57 So yeah, again on the solid state relays, you can spend the extra money and replace your standard relays.
59:03 They generally are, they can be a bit bulkier, I think Hella do one that's a straight plug-in.
59:08 It's just one of those situations where it's a bit overkill for what you're doing, but then there are situations like speed control that you need specifically to have a solid state relay.
59:18 Hopefully, that has covered relays as much as possible.
59:21 If you've got any more questions, jump in our forums and get your questions into there and we'll do our best to answer them.
59:27 Otherwise, I hope you've enjoyed this and learned something and I really appreciate you guys joining us and asking all the questions and I will see you guys in the community in the forums and future webinars and have a great day.