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Three way switch fed from light with two hots?

Posted by grimby802 (My Page) on
Thu, Oct 24, 13 at 14:58

I made the mistake of not keeping track of which was the common line when I replaced two three way switches. So I followed the basic instructions of; remove both switches, separate the wires and turn the breaker back on and see which is the hot wire. Ran into a small problem as I have a hot wire in each box. How does that work?

I have two switches each with three wires; a white, black and red wire. Black is hot in both locations. Since there is no feed source I am assuming (yes I know that's dangerous) that the power from the panel goes to the light first.

How do I go about reattaching the lines? I have tried multiple ways still cant get it.

Thanks for any help available.


Follow-Up Postings:

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RE: Three way switch fed from light with two hots?

if you have 3 wires at each switch location and you have determined that the black is common then the other 2 wires connect to the travelers. the common 'll be the dark screw


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RE: Three way switch fed from light with two hots?

Right. Tried that, switch wont work properly.

Could it be that I have a faulty switch right out of the box?

It will turn on or off at either location, except if one switch is on already the other switch wont be able to turn it off. if you turn off that switch the other will then be able to control the light.
Does that sound like a faulty switch or faulty circuit?

Thanks again.


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RE: Three way switch fed from light with two hots?

In addition to that when following the steps in the other post about trouble shooting a three way switch, i found out that with one switch out of the box completely ( no wires connected) and the power on the other three way switch could still control the light on and off.
The wiring worked before and it was a three way not a four way switch that was installed, and I changed nothing but the two switches. I also ran a continuity test and swap both three way switches to see if that was the problem - it was not.

I'm at a loss here as to how to proceed next.

Thanks again.


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RE: Three way switch fed from light with two hots?

well then the 3 way thats attached is the one with the common feeding the light source

i would assume that the issue is that the 3 way on the other end has the wrong wire on that common

try putting the white wire on the common and the other 2 on the travelers


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RE: Three way switch fed from light with two hots?

Nope. tired the white and tried the red. ? no change.

but thanks.


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RE: Three way switch fed from light with two hots?

you have a 4 way switch(es) in between?


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RE: Three way switch fed from light with two hots?

Not that I am aware of? The switches are at the top and bottom of the stairs and there isn't another switch near them anywhere. they are even in a single gang box. and there is only one light.


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RE: Three way switch fed from light with two hots?

Just a quick follow up.
I got it working. Turns out when you have two hot wires in each box, you put both the hots on travelers not the common. (on their respective switches)
Thanks for the help.


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