3 way switches shows 2 hot wires

[Doug]

I measured a 3 way switch and I got two wires on 2 different screws measuring 120 volts. I thought only one should be hot??? I'm in a rush so I can't write a lot but if looking at the switch with screws were like this

c where c is the black screw

a b

I got voltage at "a" and "c" so I'm confused. I'll google later if that will help me but does this make any sense? I will try to explain more later as necessary. I may take the wires off the switch and just measure from the wires rather than from the screws on the switch, if that matters. I want to explain more but gotta run.

[Charlie]

I could take a stab at it but I don't have time to polish my crystal ball and see what you realy have.

cb

[RBM]

If you are trying to diagnose a mis-wired set of 3 way switches, you need to take the wires off of the switches first.

[clare]

You will ALWAYS have 2 hots on a 3 way switch. You have power in and power out. There is no "off" on a 3 way switch. They are just wired that depending which way the switches are set neither "ON" of each switch is connected to the load. Switching either switch to the other position means ONE "ON" is connected to the load.

[Doug]

Based on what I read elsewhere (correct me if I'm wrong please) if I measure the voltage at the switch screws with wires fasten to them, I might get 2 hot wires but if I remove those wires and check the voltage just at the wires, I will get one hot wire.

[Mr. Austerity]

[RBM]

That is correct. With wires connected, one of the two switches will always have two hot terminals, and the other switch could have one or two hot terminals, depending upon the position of the handle.

[Roy]

Why not just "google" for "3 way switch schematic" and get the right diagrams to proceed from?

[micky]

Well it's a 3-way (that is double-throw) switch. Which is the common screw? If it's c, it will be connected to a or b at all times. So ift's conneected to a, you'll have the same votage at a and c.

If you didn't know this, you should do some reading before you fiddle with this stuff. About switches, electricity, voltage, etc.

They weren't miswired when he started, 3 threads ago. He's putting in some kind of timer, but doesn't say if he's done that yet, or if he rewired any of the switches t hat were there.

[micky]

Do you mean with no wires connected to the switch? Yes.

But at the top you were talking about screws, not wires.

But the question you ask now is just a part of a whole, and if you understood what you were doing, you could have answered the question yourself. You should read austerity's url and study every wiring situation until you understand each one of them, even if you're only goin gto use one this time . And you should probably read more than that.

[Doug]

Micky, believe me, I read a lot before I even started this job and thought I understood my 3 wire switch. Obviously I was wrong but as I wrote here, I was also reading. I do owe a lot GRATITUDE for the people here who were quick to help me. I will take your advice and read austerity's url . Thank you.

[Doug]

to proceed from?

Aside from this newsgroup, Google has been my best friend.

[Doug]

I might add to my earlier reply that I'm sure glad I bought a multitester when I did (a couple weeks ago) in preparation for this job. I don't know how I could have done this job without it.

I'm still not done as I'm waiting for daylight before I mess with the leg end of this 3 way switch to unwire it again and test just the wires for voltage. I know I can do this job that's why I refuse to hire an electrician as my wife keeps asking me. Besides, this job is making me learn 3 way switches. I still need to wire up a timer on a

2 way switch but that's easy and I chose to do this 3 way first to challenge myself.

[Mr. Austerity]

We are going to get this damn thing working yet,..... Here's how it works, this ought to help you understand just how simple the wiring really is,

[Doug]

Thanks !!!! Don't worry, I won't give up. Just glad I have a multitester to simplify. I mean if I know which wire is hot, there are only so many combinations before it has to work. Of course I'm not trying to discount the idea of learning the theory of a 3 way switch either. I want to learn the theory and with your help, others and google, I know I will. Thanks again.

[RBM]

What exactly, are you trying to do?

[bud--]

I agree if the switches are working.

If the switches work and the terminals at one end are X, Y, Z; X and Y are hot. Flip the switch and Y and Z are hot. Then this is the switch connected to power - Y connects to power (and is the "common" terminal) and X and Z are "travelers" to the other switch.

With terminals T, U, W; T and U are hot and the light is on. Flip the switch and T is hot and the light went out. U connects to the light (and is the "common" terminal).

Or, more simply if the switches work - at one switch the "common" terminal will be hot in either switch position. That is the hot feed wire.

One switch the "common" terminal will be hot only in the switch position where the light is on. That terminal connects to the light.

If you really understand how 3-ways work it isn't real hard to diagnose a problem without disconnecting all the wires. Disconnecting the wires makes it easier. (Then you run into a Carter circuit or California 3-way.....)

[RBM]

Jeeze, just when I was beginning to understand it, you throw in California and Carter!!

[The Daring Dufas]

When I do commercial wiring with three way and four way switches, I use blue and yellow wire for the travelers. It really freaks out some other electricians. I know some electricians who are clueless when it comes to installing three and four way switches. o_O

TDD

[micky]

Loads of people try, it seems. Since you can't see electricty except when it's sparking (not desired) , it sure is better to have a meter.

You'll figure it out. I had a head start on you, starting with my electric train when I was about 8.