electrical relays

[lpakiz]

If you want a simpler example of the how and why of a relay, look no farther than the key switch on your car.
Would you want to run the positive battery cable up thru the steering column, thru your key switch, then back down to the starter?
No, the key switch is merely the trigger for a relay that carries a much larger amount of current.
In the 70s, Ford vehicles had a relay under the hood on the passenger side fender. The key controlled it.
There were, in effect, 3 pin, in that the big battery cable supplied the draw-in coil as well as the supply current for the starter.

 

[ranchito]

Hey here is a three terminal relay:View attachment 728079

And the switch at terminal 3 could actually be part of a computer circuit. It is common in automotive control modules to use ground switching.

 

[tmeric7]

I use a battery and continuity tester (multimeter) to test relays. I didn't see any mention of this... sorry if I missed it. I figured this is the common method.

 

[jaxs]

I don’t understand the comments about 3 pin relays being rare.

I do,the comments are kindling for the fire of never ending debate and I said so in post #10. If you carefully read OP's first post,he ask's for information and explination of RELAY TESTERS and didn't ask for explination of how or why relays work. There isn't nor never was such thing as RELAY TESTERS and as I stated "anyone selling one is a con artist". As I suspected,people jumped on a chance to strut and preen by delving into theory of electricity which require's a library to fully understand. Electrical lend's itself to this back and forth,on and on because there are so many specialized fields and no single person is trained or understand's more than one or two fields. A master electrician doesn't understand dipole and ham operator understand's far less than electrician about temp poles. Duplex mean's one thing to ham and something intirly different to electrician. Undouptedly a ham could add a light switch or outlet that is safe but not neccessarly to code. This apply's to the countless fields so when specialty A make's a statment related to field D,specialty C & E can refute or at least minimumize A. And the beat go's on with first one then another stepping out to show how smart they are.
Ok,back to the relay races.

 

[quarencia]

There isn't nor never was such thing as RELAY TESTERS and as I stated "anyone selling one is a con artist".

umm…what’s this? Amazon.com: Electronic Specialties 190 Relay Buddy Automotive Relay Tester : Tools & Home Improvement

We could certainly debate the usefulness of the relay tester linked above, but to say they don’t exist or they’re a con is wrong. There are many others out there that work as they are intended. I don’t see the point of them given how easily a relay can be tested with a multimeter, but to each his own.

 

[tennmogger]

That relay tester is a duplicate of the one I have from Matco, model RB192, for which I paid more than twice the price. Hmmm. So, is the red one a knockoff, or is my white one a high markup namebrand, smile, probably. Either way, the tester is very handy. I have 4 trucks that use 12v relays in 4 and five pin config, and 24 volt relays of same config. I tested a couple of dozen relays today is a short time. Well worth the price of the tester. Btw, found 2 bad ones that now won't come back to haunt me.

 

[jaxs]

umm…what’s this? Amazon.com: Electronic Specialties 190 Relay Buddy Automotive Relay Tester : Tools & Home Improvement

umm... that's a gimmick device sold by a shyster to people that don't know the difference. HERE'S a few more that might interest you.

 

[detter]

LouNY had it correct. I've used these before. The case is the ground

 

[Snaker]

I do,the comments are kindling for the fire of never ending debate and I said so in post #10. If you carefully read OP's first post,he ask's for information and explination of RELAY TESTERS and didn't ask for explination of how or why relays work. There isn't nor never was such thing as RELAY TESTERS and as I stated "anyone selling one is a con artist". As I suspected,people jumped on a chance to strut and preen by delving into theory of electricity which require's a library to fully understand. Electrical lend's itself to this back and forth,on and on because there are so many specialized fields and no single person is trained or understand's more than one or two fields. A master electrician doesn't understand dipole and ham operator understand's far less than electrician about temp poles. Duplex mean's one thing to ham and something intirly different to electrician. Undouptedly a ham could add a light switch or outlet that is safe but not neccessarly to code. This apply's to the countless fields so when specialty A make's a statment related to field D,specialty C & E can refute or at least minimumize A. And the beat go's on with first one then another stepping out to show how smart they are.
Ok,back to the relay races.

Don't know what your deal is. You come on a thread (multiple posts) and whine-complain about the thread. And then blow smoke about something you know nothing about. I have worked with relay testers for years, they DO exist.

 

[Snaker]

umm…what’s this? Amazon.com: Electronic Specialties 190 Relay Buddy Automotive Relay Tester : Tools & Home Improvement

We could certainly debate the usefulness of the relay tester linked above, but to say they don’t exist or they’re a con is wrong. There are many others out there that work as they are intended. I don’t see the point of them given how easily a relay can be tested with a multimeter, but to each his own.

I don’t understand the comments about 3 pin relays being rare. They’re quite common. They’re all over the place. Just Google it. Flasher relays, horn relays, etc. Used all over the place in automotive, industrial, electronics, appliances, etc. In the general case, a three pin relay is just a Single Pole Single Throw (SPST) relay in which the load and coil share a common pin (See picture below). I’ve seen & used both NO and NC varieties. The advantages of a three pin relay are lower relay cost and you only have one common/ground connection out of the relay. Three pin relays are used less often than 4 and 5 pin relays so you don’t see them much in aftermarket because manufactures churn out 4 and 5 pin at such low cost. But for an OE buying large quantities, when a 3 pin can be used, it lowers manufacturing cost.

As for a relay tester, I suppose you could have one for the standard automotive relay form factors (Standard ISO, mini ISO & Micro ISO terminal footprints), but there’s an almost infinite variety of relay footprints out there and I don’t think a universal relay tester would be practical. Even in the ISO relay footprints, there are thousands of non-standard internal wiring configurations that would be cost prohibitive to build a tester to test them all.


View attachment 728236

picture from this article on relays…Relay article

Exactly.
Relay testers aren't designed as universal, one fits all. Just too many sizes and shapes
A tester is designed for a very few model/types of relay, often only one.
But if the user is working with dozens or hundreds of that relay, then its worth it.