Relays for Dummies (2014)

I have just bought a new horn/dip switch and want to install it. I have been reading past posts recommending that the headlight and horn both have relays installed. I know nothing about electrics, and even less about relays, so I am seeking help to work out what relays I should use, and how I should connect them.

The horn/dip switch that I have bought is this one; with four wires – green, black, white and yellow.



I imagine that black is earth; but which of the others will operate the horn, high beam, and low beam respectively? I am guessing yellow for horn; and if that is right then I guess it will not be crucial which of the others is high beam or low beam; one switch position will be high; the other low. Can anyone put me right?

If I was to connect this switch directly to the harness, as my existing switch is, it would be relatively simple to connect the horn (yellow) to brown blue; earth to the earth wire in the headlight; and the green and white to blue white and blue red; just replacing the wires from the old switch that I will take off.

But if I buy and use relays I get confused. The first issue is what relays I should buy. Should they be 12 amp; 20 amp, or more? As I have a 20 amp fuse it seems logical that the relay should be at least 20 amp so that it does not blow before the fuse. Should it be higher, say 30? Or lower?


And now the confusing stuff. From what I have read I anticipate that the relay for the horn should be a four pin relay. Something like this?




If the yellow wire from the switch is the horn wire, then I will need to connect the yellow wire to the “switch” side of the relay. Do I also connect the black earth wire? Or does that just go to an earth point on the bike, like the one in the headlight. And do I then need to connect another earth from the switch side of the relay to an earth point?

And on the other side of the relay do I connect the brown black wire from the horn circuit? But what about the other pin? Do you put an earth out of the relay, on the same “side” as the brown black so that the circuit is completed without going through the switch?

I probably have got the above wrong, but I get even more confused when it comes to the headlight relay. I understand that because this circuit is not just an “on off” circuit, but is either one circuit (high beam) or another (low beam) I need to have a 5 pin relay that can handle the two circuits.

Something like this?




logically on one side of the relay I should connect the green wire and the white wire from the switch; as one of these will be high beam and one will be low beam. And on the other side of the circuit will be the blue/white wire from the headlight and the blue red wire from low beam. But what about the fifth wire. Is that an earth? As the blue white and blue red are already earthed, is there an earth from the relay to create a circuit from either the green or white wire from the switch? If so, do I just connect it to any earth point? Or is the black wire from the switch already creating the earth, even though it is connected to the horn switch circuit.

Or am I just wrong.

I would be very grateful for input.

All relays contain two terminals or pins for the coil. One of these is earth, the other is connected to the switch or device meant to actuate the relay. Generally, the relay has an imprinted circuit diagram showing the coil terminals. If the relay is electromagnetic (not solid state), it does not matter which terminal is connected to earth.

The remainder of the terminals on the relay are the contacts. The number and function depends on the relay's configuration. Relay and switch configurations are given by numbers of "poles" and "throws".....example, single pole - double throw, double pole - double throw. These are abbreviated as SPST, DPDT, etc. There are other configurations. The pole is where the electrical source is connected, the throw is where the electrical source is directed. The contacts are usually shown on the relay terminal diagram as an arrow and dots. The "tail" of the arrow is the pole, the head of the arrow touches one of the dots, and this is the "normally closed" throw. The other dot represents where the throw is directed when the relay is energized, and is the "normally open" throw.

While this does not specifically answer your question, an understanding of this terminology will be a helpful
start.

I suggest you get a simple volt-ohm-meter (VOM). These can be obtained rather inexpensively ($10-15) and are very useful in auto and home use. The Ohm function will tell you which of your switch circuits are horn, upper, lower beam etc.

Ideally, the relay amp capacity should be about 25 to 50% greater than the maximum expected load on the most critical circuit....example if a double pole relay has 10 amps on one pole, and 15 on the other, use a 20 amp relay.

Slick

Micro needs less real estate http://www.motorcycle-superstore.com/24 ... icro-relay
Any friends with electrical skills?

concours said:

Micro needs less real estate http://www.motorcycle-superstore.com/24 ... icro-relay
Any friends with electrical skills?

Click to expand...

I can help, but I am on the road and cannot post sketches or diagrams. Moreover, I am not familiar with Cdo wiring colors and practice. If Chris can post circuit diagrams of his switch and proposed relays, I can provide some general help.

Slick

plug and play

http://www.cycleterminal.com/horn-kits.html

This might be helpful

Pete

You have it pretty well for not knowing about relays. One thing I might mention is that some relays have a built-in diode across the coil to prevent a reverse inductive spike when the coil turns off. In this case the polarity would be important. Also don't forget that our bikes are positive ground. Isn't there any info that comes with the switch that tells what wires are what? It would be pretty simple to figure out if you do obtain a cheapo VOM as described by Slick.

Relays in our +earth headlight shells is as simple as a 3 way chess game plan. Cdo hi/low beams are wired weirdly to relay simply, IIRC earth paths change rather than power supply. I ended up with 3 relays in Peel shell, one to activate with key on to supply power to shell, then from the 1st main relay out to 2nd to supply low beam and 3rd relay for hi beam. There are half size 30 amp relays that make stuffing inside shell easier. Unless you rework the factory way the hi/lo beams are wired hi/lo is not as straight forward as horn which just needs one relay between horn button and power.

Youtube > 4 and then 5 pole relays for their electrical logic clarity.
Settle on which color wires you want the bar light/horn switch to feed to, say, black for earth, yellow to low and white for high and left over wire for horn, then set up so key on sends relayed power to bar switch then figure out 2 more relays or a single 5 pole to get hi and low relayed. I made one common earth connection all the earth wires meet at in shell, ie: the relay switches earths and their hi power flow paths. The hi/low beam indicator lamp adds more electrical logic to get right too along with the momentary dip button.

Chris i have 4 of those micro type relays and also you can get a base for them that hold the wires. So if you remove the relay you just pull it off the base without have to take wires of one at a time and remember which terminal wire go on. Also i have a short length of wire of same size as high amp feed with suitable terminals on it so if relay or switch were to fail i can remove relay fit the wire to connect lights or also ignition in my case straight to battery (via fuses) as a get you home measure.

You can put relays in at a later time and it won't change any of the wiring in the handlebar switch. So I recommend wiring the handlebar switch first. Wiring your replacement switch will be the same as wiring your original switch. You just won't have the high beam flash switch anymore. The white wire will no longer be connected. Seeing that you don't have a wiring diagram for your new switch assembly, get yourself a cheap multimeter. One that checks continuity with a beeper is a nice feature.

The horn button will go directly to ground (i.e. handlebar) when pushed. Just check continuity between the switch contact and one of the four wires. Once found, that is your horn wire. Connect that to your brown and black wire.

The other three wires are for the headlight high/low beam switch. When the switch is in the high beam position check continuity between two of those three wires. Then switch it to the low beam position and check continuity between two of those three wires. The wire that has continuity between the two wires in both positions is called the common position of the switch and will go to the blue wire that comes from the headlight switch.

Now when you are in the high beam position check continuity between your common wire and one of the other two wires that has continuity. When you find that wire, that is the wire that goes to your high beam lamp which is the blue and white wire. The low beam is the other of the two wires which goes to the blue and red wire. You can double check that with your meter. Once wired and mounted and wired on your handlebar both headlight and horn should work fine.

Here is a headlight relay diagram that might help you. The wires I have drawn in bold are wires that you would need to add to your existing circuit. The pin callout for the relays is the same for both mini and micro relays. This diagram shows 5-pin relays however a 4-pin would work fine. If you use 5-pin relays I would recommend wiring pins 87 and 30 the way I have shown in this diagram. You can swap pins 30 and 87 around but the way I have drawn it pin 87A would never be hot so you would not need to protect it from ground. Pins 85 and 86 can be swapped as well however there are relays out there that do have diodes instead of resistors in them. If you get one of those with a diode the side of the relay should tell you what pin should be plus or minus.


Headlight Relay Diagram


I am assuming this is for a 1970 Commando. If it is for a 1971 or newer the horn wiring would need to be modified. I hope this is of some help,
Pete

Guys, thank you very much for the input to date. The relays for the headlight are a bit more complex than I was anticipating. Pete; that diagram is very helpful thankyou, and yes it is for a 1970. Given the need to run a new wire from the battery, as well as some others it will be a bit of a major; necessitating removing the fuel tank (I have only just put it back after fitting a new twin output coil); and some real weekend time. So I think that this project will be a bit longer term than I first anticipated, but I might be able to get the horn relay done when I instal the switch; that seems a bit more straight forward.

I note the comment that the horn earths direct to the handlebar. I had thought that was the case too; but became uncertain for two reasons; first when I was trying to my current ducon horn switch to work better, I was fiddling with it with a screwdriver, with the switch connected to the circuit but taken off the handlebar, and the horn went; presumably my screwdriver hit the earth connection in the switch and formed a circuit. That made me wonder if the switch was wired to use the earth wire in it for the horn, rather than the handlebar. Second, the new switch that I have bought has a plastic base, and the "push" on the switch will not directly touch the handlebar; it is internal. There is a metal band connecting the switch to the handlebar, and I guess that this could be the earth connection. No doubt I will find out when I get into it. I am suspicious that my handlebar does not have a good earth connection, and I am thinking about running a separate earth wire from the base of the switch to an earth point on the frame.

I do have a voltmeter, and will test the switch to see what wires go where. I didn't know that you could use the voltmeter for this when the switch was not connected to a live circuit; can I just put the voltmeter to an ohm setting, and connect one clamp to the earth wire; and another to green or white, and see if it is live; or do I have to get a power source into the circuit, like a battery?

In NZ we have to get our vehicles certified annually; it is called a "warrant of fitness"; and as part of that process our horn and headlights are checked - including full beam and dip. My warrant has expired, and I am due to go on a trip in two weeks (down to Whangamata to the Best of British Festival; where a bunch of ((sad old - including me - according to my wife)) people get together with their British cars and bikes - as opposed to the Beach Hop also at Whangamata where American car enthusiasts - thousands of them - party for a week; but I am really off topic now). So I have to get my light and horn working properly; this weekend, so that I can get a new warrant before I hit the road. They are semi functional now; the ducon horn button sometimes works - but the horn is very sad and irregular, and the high low beam also works if I keep my hand on it and keep pushing firmly; as soon as I let go it changes. Right now I am wondering if I just give the warrant a shot with the present switch, and properly fix it when I can put more time into it. Given the need for some reasonably substantial additional wiring, and possibly also to change some connectors from bullet connectors to connectors compatable with the switches (presumably spade connectors?) I can imagine that this will take me longer than I first thought; (and my experience is that everything I do takes about three times the initial time that I estimate). Any further input will be appreciated; and if this thread dies for the moment I expect that I will revive it when I actually get onto the work.

@Chris:

When using the Ohm function on a VOM, you DO NOT want a "live" circuit. Use the DC volts function when the circuit is live.

The Ohm function is used to check for "continuity".... That is, to check if one wire is continuous with itself, or connected to another. You do this by isolating (disconnecting) wires from the main circuit, then connect one lead of the VOM to one wire, and with the other lead of the VOM, probe about until you find a wire that makes the needle of the VOM go to zero ohms. When this occurs, the two wires so connected to the VOM leads are "continuous" either as the two ends of the same wire, or are connected via a switch or relay.

To make this clear:I
Switch your VOM to Ohms, plug meter leads into the plus and neg. terminals on the meter. Notice the meter needle reads infinite ohms....this is an open circuit. Now touch the bare ends of the meter leads together....the meter needle moves to zero ohms....this is a closed circuit. If you take a piece of wire, strip some insulation from each end, then connect one lead of the VOM to one end of the wire, the other VOM lead to the other end of the wire, the meter needle moves to zero and tells you that the intervening wire is continuous...that is...does not have a hidden break in it, or if the intervening wire were in a bundle, the meter tells you that you are connected to opposite ends of the SAME wire.

You use this technique to check which wires become connected when a multi-function switch such as your handlebar switch moves thru its functions.

I hope this is not too pedantic.

If your switch has a plastic (insulated) base, there may be one wire intended for an earth wire. You will have to connect one VOM lead to a wire ( any wire), then check for continuity with all other wires, and also to the metallic shell of the switch, to find what connects to what.

Did the switch not come with a circuit schematic? If so, can you post it? With such a schematic, there are many on this forum who can help you make it work.

Slick

I got to thinking after I made my post that you might be able to just pull the cover off of your new switch assembly and physically see where each wire goes. I am not familiar with that switch so it is just a thought.

I also forgot that your motorcycle should have an ammeter. If it does, instead of running a wire from the battery to the headlight relays you can connect the wire to the ammeter terminal where the brown and blue wire is connected. A fuse would then be optional. I don't know why I didn't think of that earlier because I have added an ammeter to my 1974 Commando when I rewired it and then tapped my headlight relay power right off of the ammeter.

Just to pass your test you obviously don't need any headlight relays. As for the horn you may need to take the handlebar off and clean the top yoke where the handlebar rests to make a good electrical connection. Also make sure that all of the related electrical connections are clean and secure. If all else fails the horn itself may be at fault - the points inside the horn can get corroded.

I have had trouble with the WIPAC handlebar switches on my BSA's and unfortunately they are just not made to be taken apart and worked on...that is if you want to get them back together and working again.

Good luck with your project and passing your test.

hi , not being very good with relays i bought a kit from easternbeaver who use micro relays and do kits in positive earth the owner use to have a commando and no what he is talking about hope this is helpful

I bought the same kit from eastern beaver. Even an electrical moron like me was able to wire it in with no problems!---Mike.

Again thanks for the input. Peter, the option of connecting to the ammeter connection is good. Ironically I just spent much of last Saturday glueing my 1 year old genuine Lucas replacement ammeter back together after the bottom had parted company with its case - which I discovered in the process of mucking around with the dip switch: I am not sure if I had put too much strain on it in connecting the harness to it; glueing it back together only took a minute, but the I couldn't press the base into the case, and spent over half an hour with a dremel grinding it down to fit. Given the failure of that (I bought it to replace the original, which had a needle that waved around so much as to be useless), and the failure of the Ducon switch I am really wondering about the quality of some modern replica parts.

I know that some members advocate disconnecting the ammeter from the main harness because of the inefficiency of having the main harness run through an instrument in the headlamp shell; I really like to have it there, and find it useful to check that the circuit is live when I start the bike; see the drain from the light - it confirms when the light is on dip or full; which is useful when my dip switch is not working, and I am testing the light in daylight. I have taken the precaution of putting heat shrink over the connectors on the ammeter, so that the live circuit is not exposed in the headlight, as it otherwise would be.

And the Eastern Beaver option is good; I will mull that over.

If the earth from the new switch is through the handlebar, I am also wondering about running a separate earth wire from the base of the switch along the handlebar with the other wires to an earth point - probably the head steady where the ignition is earthed, which seems like a way to ensure a consistant earth connection.

I have had my share of frustration with replacement ammeters as well. The one I bought was sold by Wassell and the first thing that went wrong was that the plastic case had cracked where the chrome bezel was crimped so I machined an aluminum case for it. Then shortly thereafter one of the terminal studs broke free from the coil winding inside due to a cold solder joint. Then finally the instruments pointer needle warped and dragged on the instruments glass. I tried straightening the pointer by using heat and unfortunately I used too much heat and the base of the pointer shriveled up. So all of that work for nothing!

I had just rewired my motorcycle and I was pretty much committed to using an ammeter now. So I went over to my BSA and stole the ammeter out of it which is actually an American 1 inch diameter 'ruggedized' miliamp gauge made by Ideal Precision. I machined a new case for that gauge using the Wassells glass and bezel I now have an instrument that works perfectly. It is probably the best analog ammeter that any British bike has ever seen. Now I want to get another one of those instruments to replace the one on my BSA and I don't know where to find one!

I don't know what Lucas was thinking with that gauge. Hardly anything sticks to phenolic and that is the material on the bottom of the gauge. Of course it is going to fall apart! To make matters worse the Lucas gauge uses the exact same meter movement as the Wassell ammeter that I previously described. So whenever you want to get another ammeter maybe the ones made in India or China are made of a better quality.


Adding a redundant ground to your handlebar switch is probably a good idea. It would be neat if you could put the ground wire inside the switch itself and then run it along with the other wires. Maybe you can solder it to the metal frame or something. I think it would look better that way rather than having a wire grounded externally to the switch.

G'day,
Pete

I am making some progress. I got the new switch installed over the weekend, and before that managed to work out what wire was what with my voltmeter. In case anyone is interested; white is common; black is horn, and green and yellow are dip and high beam; I can’t recall which I connected to which.

I also went out and bought three micro relays. They are five pin; 12 volt; 30 amp. Instead of having the codes that PeterJoe used on his diagram – 85, 86, 87, 87A and 30, they have 1,2, 3, 4 and 5. I have posted a (not very clear) picture of one of them.

From the diagram on the relay I am guessing that 1 is the equivalent of 85 - for attaching the wire from the switch (blue red or blue white, as the case may be); 2 is the equivalent of 86 - an earth from the switch;l 3 is 30; which connects to the lamp (high or low beam), and 5 is where the power from the battery is connected to. Is that right?

ugh dyslexiks stumble on converting number codes but can make universal relay sense out of this practical visual examination
[video]http://www.youtube.com/watch?v=Tw9QkkT2ptU[/video]

@Chris

"From the diagram on the relay I am guessing that 1 is the equivalent of 85 - for attaching the wire from the switch (blue red or blue white, as the case may be); 2 is the equivalent of 86 - an earth from the switch;l 3 is 30; which connects to the lamp (high or low beam), and 5 is where the power from the battery is connected to. Is that right?"

Can you sketch relay diagram, take pic, and post? Relay mfgr's are not bound to standardization for number system. It is a pure guess what the numbers correspond to.

Or else: use ohm function to determine coil terminals.....these will have low ohms, but not zero across them. The battery terminal (pole) and NC terminal will have zero ohms across them, and battery to NO terminal will have infinity ohms (open circuit) across them. Once you have identified the coil terminals, the others fall into place.

Slick

OK you bought a couple micro relays that didn't use the standard ISO numbering system. That's OK because they gave you a little diagram on the side of the relay.

Number 1 and 2 pins = pin number 85 and pin number 86. These wires are for the electromagnetic coil. These two wires can be used interchangeably.
Pin number 3 = pin number 30.
Pin number 4 = pin number 87A. This pin is not used.
Pin number 5 = pin number 87.

Here is a diagram of the pin call out while looking at the base of the relay.


Basically the two outer 3/16 inch wide terminals are for the electromagnetic coil. The two quarter inch wide terminals will power the headlight.

If you wire these incorrectly nothing bad will happen, no smoke will appear and you won't damage the relay or any other component. The worst that can happen is that it may blow a fuse. But most likely It just won't work the way you want it to work.