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Three-way switch problems

I'm having a hard time with a couple of three-way switches that control one stairway light fixture.
Half of my house is still on knob & tube.

The switches haven't worked right since I moved in so I decided to tackle the problem.

Downstairs I have a switch that has three black wires coming to it. I ID'd the hot wire and did continuity tests to confirm that the other two are travelers that go to the other switch upstairs. At THAT switch, however, there are 2 white wires and one black. (both white are travelers)

I followed the wiring instructions carefully to connect the travelers and the common to both switches but when finished, and after disconnecting and rechecking two more times, when fully wired the light will only turn on when the downstairs switch is in the 'up' position and the upstairs switch is also in the up position. If the downstairs switch is 'down' then the light will not go on regardless of the upstairs switch position.

The only way I can make any sense of this is if the light fixture is inline on one of the traveler lines. Anybody have any other ideas / advice or if I'm right can anyone tell me how to fix the problem, hopefully without a lot of destruction?

Re: Three-way switch problems

I assume you have checked or replaced the 3 way switches. But, a word of caution switches will sometimes check good with a sensitive ohm meter but "open" if asked to carry a load.

It's going to be a little harder to troubleshoot this problem because you don't have a neutral or ground at the switches to take voltage measurements from.
An easy way is to simulate the 3 way switches with jumper wires and insulated alligator clips.

It's obvious someone didn't follow code or common sense because the travellers aren't the same wires on both ends.

Try checking in the light box. Make sure the travellers go directly to the switched terminals on the switches, not the commoms.

Good Luck, from Columbiana, AL

Maurice Turgeon, thesemi-retiredelectrician.com

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