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I have a pair of 3-way switches in the basement, the switch furthest from the power source is by a walkout door. There is a light outside the door which uses a switch that connects to the 3-way switch...which means the outside light switch only works when the basement light is on. In some ways it is nice since I never leave the outside light on unintentionally...but on the other hand I have to keep the basement lights on when using that light, and anyone else can shut off the basement light (and the outside light) when I am outside.

I'd like to get the outside switch to work even when the basement lights are off. I was wondering if replacing the single pole switch with a 3-way switch would allow me to do this. In my head it makes sense, I have 2 travelers, one of which will always have power. My only concern is that it might not work the way I think and leave the outside light on all the time. Is this possible?

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  • I think it gets power from the light(controlled by the three ways). A second light with an added switch in between.
    – crip659
    Feb 2 at 22:45
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    Please include more detail about the wiring. If you're comfortable doing it, extend the switches out of the boxes and take photos showing how the conductors connect to the switches and how they are grouped into cables or conduits. Also indicate how/where the basement lights are tied into the switch circuit. Finally, is the basement finished or unfinished?
    – Greg Hill
    Feb 2 at 23:05
  • I measured the wires and there are only 2 travelers, 1 having power at a time. There is no other source of power. The basement is finished, this section has 3/8" plywood over foam blocks, the switch box is in the foam. It's not something I'm thrilled about taking apart to run new wiring but it's something I can manage. I was just thinking there is always power there, why can't I use it? Smart 3-way switches tap into that, I'm just surprised there isn't a switch out there that can handle this situation.
    – rtaft
    Feb 3 at 17:12

3 Answers 3

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Smart Switches to the Rescue!

A normal 3-way switch setup has:

  • Two travelers - at any given time, one has power and the other doesn't. If the one with power (based on "switch 1") is connected to the switched hot ("common") on switch 2 then the light goes on.
  • A third wire that can be: neutral, always hot or switched hot

In order to add a separately switched light or an always on receptacle, you need to have both an always hot wire and a neutral wire in the same place. Depending on the wiring configuration, you may have that in "switch 1 box", in "switch 2 box" or in the "fixture box". You will almost certainly not have it in all 3.

Some smart switches are designed in a way that they can perform 3-way style switching without traditional travelers. They communicate in some fashion to get the job done. Some smart switches actually rely on traditional 3-way traveler wiring (or a slight modification) because that is easier as a retrofit - but that won't help you here.

It is likely but not guaranteed that your setup could be resolved by replacing each switch with an appropriate smart switch (they will be the same product line but probably not exactly the same product in each location) and some thoughtful very specific rewiring. To tell for sure we'll need clear pictures of the wiring in each switch box and identification of the wires.

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It may be possible, depending on what wires are available in the outside light switch, but it will not work the way you are expecting or hoping. If you have both travelers in the outside light switch box, a three way switch would let the switch always change whether the outside light is on or off, but which direction is on or off will change depending on the other three-way switches. The two states for the outside light switch may be "on or off along with the basement lights" and "On when the basement lights are off, but off when the basement lights are on". There are many ways that three-way switches can be wired, so it could work somewhat differently, but it will never be simply "up is on and down is off".

It's possible that there's an always-on hot wire in the outside light switch box, or in the basement light box that's right there, and the outside light is just wired wrong. If you get this lucky, you don't need a new switch, just fix the wiring. You would have to open up the two switch boxes by the outside door and check the wiring you have. If you do that, turn off the breaker first, and always take pictures of the wiring you currently have before undoing any of them.

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  • There is no always-on hot, only one or the other traveler has power.
    – rtaft
    Feb 3 at 16:36
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The outside light is most likely powered by the switch leg of the 3-way. Some thoughts:

  1. if there is constant power in the 3-way box, then use that to power the single pole. (there must be a neutral for the light, so there is likely a power feed in the box)... but...

  2. If the 3-way at the load end has no constant power (neutral and travelers are fed from first 3-way via a three-wire cable, and switch leg for 3-way is in the box), then you might not have input power, in which case the neutral is used for both lights, and the switched power is shared. In this case, you would need to add input power (run power from somewhere) to make the outside light work without the 3-way light.

If you can show the wiring the answer will be more simple.

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