I am replacing these two switches and not positive how the right switch is wired. The left switch is the only switch that runs to our porch light and the right switch is the only switch that run to the interior room light. It looks like it is a three way switch, but I am not sure since each of those switches operate as single pole switches.

Second question, even though the switch is grounded to the box, how can I tell if the box is actually grounded?

enter image description here

  • It is very difficult to tell, from the photograph, which wires go into which connector blocks. Apr 7, 2016 at 4:06
  • What country and state are you in? Wire color codes vary from place to place. Apr 7, 2016 at 4:07

4 Answers 4


It looks like it is a three way switch, but I am not sure

It isn't. What I see is

enter image description here

That seems fairly straightforward to me

  • The black wires are permanent line (live/hot/phase)
  • The red wires are switched line (live/hot/phase)
  • The white wires are neutral
  • The green wire is a ground (earth) bond between switch housing and metal wall-box

So, I don't see a three-way arrangement (two switches controlling one light)

Whether the use of colours is compliant with local code (regulations) depends on where this is located and when it was installed.

Sorry for the horrible diagram, I must find a better tool than MS-Windows-Paint!

As bib pointed out in a comment, my diagram omits one black wire from the left switch to the bottom left (room light) cable. I conjecture that this may have been to provide power to something like a ceiling fan with a separate pull-switch built into the hub - but that's just a guess on my part.

how can I tell if the box is actually grounded?

It probably isn't, unless there is a connection to the back-box we can't see (perhaps to the outer metal sheath of an amoured cable.

You can test this with a multimeter and, with all power to the building turned off and verified off, measure resistance between metal-back box and the white wires. If the resistance is low there is a ground connection between back-box and the neutral-ground bond near the main incomer or main panel.

  • I think I see a black and a red on each switch in addition to the jumper.
    – bib
    Apr 7, 2016 at 11:55
  • @bib: You are right, there is an extra black heading off towards the room light. The arrangement doesn't look like a thre-way with traveller though. Maybe there is provision for a ceiling-fan with a separate pull-cord switch or something. Apr 7, 2016 at 13:35
  • Wouldn't the the switch be grounded via the metal mounting screws and the metal box? Or this doesn't matter since we don't know if the box is properly grounded?
    – junta
    Apr 7, 2016 at 14:13
  • @junta The box is only grounded if there is a ground wire from the panel attached to it (not showing), or the armor from an armored cable is properly attached (also not showing).
    – bib
    Apr 7, 2016 at 16:48

I see two black wires and one red wire connected to each switch. If, for each switch, the two black wires are connected together, you have a bog standard pair of single pole switched circuits, with unswitched power also continuing on toward one of the loads.

The two black wires at each switch may be connected together by being clamped into the same terminal block, or into separate terminal blocks that are connected together inside the switch. That's why I want to know where you are, and I want to see a better view of the back of the switches.

  • I am located in Colorado. The black wires appear to be connect into separate holes but connected together.
    – junta
    Apr 7, 2016 at 14:06

Thanks for the help. The extra wire was from an old fan/light fixture, which is no longer there. That is where my confusion came from.


Assuming you are in the US, a quick way to tell if a switch is a three-way is that it will not have the words "off" or "on" on it; threeway switches can be mounted in either direction.

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