Relay Test

[hojo in sc]

How do you test the relay to make sure it works?

Thanks in advance.

[ligito]

Use a meter, or a test light, or a 12 volt bulb connected to the output circuit, to see if it works.

This is assuming you have it completely wired.

[ligito]

Hot wire from battery to 30
Ground to 85
87 to load (lights or horn that are grounded)
positive from a switched source to 86 (any hot source, like the hot output side of a light switch)

You can also plug it in to replace another relay and test it that way

[crazykz]

Thread post #14 in this thread talks about relays:
http://www.st-owners.com/forums/showthread.php?t=7931

Ligito has it but I'll try too. A relay is a coil and a contact. Each one of these has two terminals. So 2*2=4 which equals the 4 terminals on the relay. The way it works is when you apply 12V to the coil it causes the contact to close. What this means is that when the contact closes it connects the contacts two terminals together like a wire. Just like turning on a light switch sends voltage to the light.

http://www.the12volt.com/images/relaytext2.gif

So in order to test a relay you need to get the coil to close. To do this hook 12V to one side of the coil and ground to the other side of the coil. So hook a ground to pin 85 then get a wire with 12V on it and touch it to pin 86 . When you do this you should here the relay click meaning the contact closes. If you let off the 12V wire the relay contact will open. If the relay does click the chances are the relay is working but you won't know for sure until you connect something across the contact terminals (pin 30 and 87) to make sure the contact is closing.

So you can connect 12V to pin 30 and then hook something to pin 87 that requires 12V. You'll can connect the ground for the device to the same ground you used for pin 85. So now when you apply 12V to pin 86 it will close the contact and send the 12V on pin 30 through the contact and over to pin 87 which is connected to something that will work when 12V is applied to it. Voltage doesn't work without a ground though so the device must also have it's ground wire connected to ground.

Hope that helps. If you buy a small multimeter this is a lot easier to do. I recommend this one from Radio Shack for $30. If you own a bike, or if you plan on doing any electrical work (like playing with relays) you really need one.

http://rsk.imageg.net/graphics/product_images/pRS1C-2266866w345.jpg


Curt

[Bones]

I once tested a relay by having each member of the team hand off the baton to the next member, at 100 meter intervals. Seemed to work OK.

[BigTom]

Hummph

We slower fellows tested at 25 meter intervals, hence the 100 m relay. We would routinely get it done in 30 seconds or so, didn't seem to work so well. Some relays are clearly quicker than others.

Hojo:

Curt gave you the lay down deal, my nonsense aside. There are cheaper and more expensive multimeter's (Harbour Freight to Snap On) but you just about need one. If you are like me, you either need Auto Ranging which automatically sets the appropriate voltage/amperage/wattage so you don't blow the meter up testing 240v when you have it set at 14v. Or the much cheaper model so it doesn't hurt so much to replace:)

[Gonzo]

Last relay I tested, I did the bike part and my partners did the swim and run parts.
Gonzo

[hojo in sc]

Well, just call me stupid. I forgot that there was an extra fuse inline with the relay, and it blew cuz I was messing around with some other wiring stuff and grabbed the wrong wire to conect:soapbox