Electrical – 3-way light switch thesteriously works, then stops working, then starts working again

electricallightingmultiway-switch

I have a three-way light switch that is exhibiting really odd behavior.

Sometimes it works and sometimes it does not. For example, just now the following happened.

  1. Lights are off. I go to switch A and flip it back and forth. Nothing happens.

  2. I then go to switch B and flip it. The lights come on.

  3. I then return to switch A and flip it twice. The lights first go off, then come on again.

For about a week, neither switch was working and lights just stayed off.

It is very strange. What might be the problem here?

Note that these are dimmable lights and that there are a lot of light switches in the house so it is possible the circuit is tied into something else. Can you have a 4-way light switch?

Best Answer

Normal 3-ways are wired like this

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Your first part suggests a 3-way circuit where one of the switches is miswired.

There is such a thing as 3+ switches on a 4-way circuit. Thise switches are added to the middle, and take 2 yellows on one side and 2 yellows on the other side. They either send them straight through, or swap them.

I use yellow for travelers because they are a matched pair that are interchangeable. Practical 3-way wiring with cable forces you to use 2 of the 3 available wire colors for travelers, and it can be different on every wire run. As such, I recommend removing all uncertainty by marking them with yellow tape. It makes complicated things dog simple.

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