Why aren't my three-way switches working?

Question

I've searched on this site and many others, and have not been able to discover a solution. I was wondering if you guys could help me out.

I have 2 3-way switches in my hallway that control a set of two lights. It used to work perfectly. However, recently one switch would only work when the other was in a specific direction (i.e. they weren't toggling as normal). So I changed both switches, assuming one of them had gone bad, attaching the wires exactly as they were before. Same problem.

Looking into the problem a little further, I broke out my voltage tester and discovered that the hot wire was hooked up to the common on the first switch. But, the second switch wouldn't get power unless the first switch was in on position. The travelers on the first switch seemed set up normally - one was on when the switch was in one position, and they would switch when I switch the switch position. However, the other switch only got power when they were in one position, and the lights wouldn't turn on unless the second switch was on. To further complicate matters, all the wires are black. There are no red wires, and all the whites are wire-nutted in the back. Additionally, the hot wire coming in to the first switch is wire-nutted together with another black wire, which brings power to another light fixture in the house.

Thoughts? I can't figure it out.

Answer 1

This sounds like one of the traveler wires failed open. To troubleshoot:

1. Turn the circuit off, of course!
2. Take a continuity tester, and attach a long piece of wire (as long as the stairs) to one of the probes.
3. Attach the other end of the long piece of wire to one of the travelers (black wires) at the upstairs box.
4. Probe the black wires in the downstairs box with your continuity tester -- one of them should have continuity.
5. Repeat steps 3 and 4 for the other traveler in the upstairs box.

Once you verify that it's a broken traveler...you can either:

1. Reuse an intact white wire between the two switches as a traveler by disconnecting it from the neutral junctions at both ends and rewire it in place of the faulty traveler and tagging it black or red with paint or tape at both ends.
2. If you don't have two white wires running between the two switch boxes, or if your wiring is in conduit, you'll have to pull new wire for the traveler -- either a new wire through the conduit after fishing out the broken traveler, or a /3 cable of the same type and gauge as the existing cables if there simply isn't a wire to repurpose.