I have a 3-way setup with one switch at the top of the stairs and one at the bottom for a light at the top of the stairs. It all appears to be wired fine and I have power and light but the switches are not working to turn the light off. Please can someone give me an idea where to check as I have triple checked all the wires now?!

The top switch has been wired with a black marked live wire which I have then wired into the light fitting with the other live wires.

I am not sure if this is to do with the switches, fitting or something more advanced?

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  • Is "fitting" synonymous with "fixture" in your part of the world?
    – isherwood
    Commented Feb 2, 2016 at 20:08

1 Answer 1


First, just to prevent any confusion, it's a "3-way" switch setup, not 2-way. 3-way switches take power in (or let it out) through a singular wire, which then is switched between two 'traveler' wires. It's referred to as a 3-way switch for the same reason as a 3-way intersection - there are 3 paths in/out of the switch.

Next, you need to ensure that the wires leading to and from your switches actually go to the light. This probably goes without saying, but if you've changed the light's wiring as well then that could be the issue.

However, the final solution will always come down to the wiring or the devices. The light itself does not control switching, so it is not bad. You might have a wrong switch, bad switch, or again just have some wiring incorrect. Follow this diagram below and it'll work:

3-way switch wiring diagram

The diagram might not be the exact layout for your situation as the power could be coming in at the light or the light could be between the switches. Regardless, that would simply call for wire nut connections and it would still come out to this exact setup.

  • Thanks. I replaced the light and switches but simply kept the same cabling. I think power is coming into the light from what I can see. I have the two switches linked by a red wire in the comm port and yellow and blue in L1 and L2 the same in both switches. I then have a black cable tagged live in L1 of the main switch and the other live red cable in L2. I have one black neutral linked to the light fitting and then the 2 live red cables and 1 black tagged live cable all linked into the live socket on the fitting. All of that seems fitting with a standard mapping from what I have seen? Commented Feb 2, 2016 at 20:05
  • @user3775259 -- can you please add a diagram of what on Earth is going on with your wiring to the question!?! Commented Feb 3, 2016 at 2:04
  • @user3775259 -- also, where in the world are you? Commented Feb 3, 2016 at 2:04
  • Whoops, my bad. I was basing my answer on the US electrical system.
    – TFK
    Commented Feb 3, 2016 at 3:13
  • Sorry, should have clarified I am based in Guernsey just below the UK so follow UK system. I will try and add an image of the wiring route.... Commented Feb 3, 2016 at 7:43

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