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enter image description hereenter image description hereWe’ve been swapping out all our outlets and switches in our house....with minimal problems until today.

In our living room we have a dimmer switch on one wall that controls our overhead light. On another wall, we have two switches (in one box). One controls an outside light. The other switch was a mystery to us. It did not turn on the overhead light and did not control any outlets. We assumed it was a dead switch.

We replaced the dimmer switch first. We found a black and red wire pigtailed and connected to the common screw and a white on the other screw. We connected it the same way and its worked perfectly for the last few days.

Today we tackled the wall that had the outside switch and “dead” switch in one box. The outside switch replaced easily and works fine. When we pulled the dead switch, it had a red, black, and white wire on 3 separate screws. So we put in a three way switch to replace it.

When we turned the power back on, we figured there was no way to “test” it. But then I noticed the new dimmer switch for the overhead light no longer worked. After scratching our heads for a few minutes, my husband flipped the “dead switch” and the overhead light came on. After some testing we learned the “dead switch” wasn’t a true three-way switch....but wasn’t really dead either. It seemed to merely provide power to the dimmer switch. The dimmer switch provided power to the light. But if the dimmer switch was off, the “dead switch” couldn’t turn on the overhead light (which is what we had tried earlier when researching the switch).

We were fine with the setup....so we shut the power off again and went about getting the switches back in their boxes and putting the covers on.

Once that was completed we tested everything again. Now we have no power to the “dead switch”, hence no power to the dimmer switch. We took everything back out, disconnected the three wires, and turned the power on. None of the wires are showing power for the dead switch (and therefore none of the wires for the dimmer switch show power either).

All other outlets and switches on that breaker are working fine (including the wires in the same box for the outside light...) and we never tripped a breaker.

So what could have happened? I’m thinking my husband may have connected the wrong wire to the common screw initially.....but 1) why would it have worked and 2) could it have then shorted something?

Any thoughts or ideas will be appreciated. We’ll be calling an electrician....but we’re really scratching our heads right now.

  • Did you match common screw from the old 3-way onto common screw for the new one? Are 2 of the 3 wires going into the same cable, and are these the ones not on the common? – Harper Mar 15 at 20:52
  • Any chance you can post a photo of the box with the switches pulled out? – Harper Mar 15 at 20:54
  • Any chance there's another three way switch that may have been flipped. – Platinum Goose Mar 15 at 21:23
  • We’ve checked all the gfci outlets in the house to ensure none of them tripped. We haven’t found any other three way switch that could work with this one. – Mary Mar 15 at 21:38
  • The dimmer may itself be a 3-way switch - i.e., one side is the "dead" switch and the other side is the dimmer. So in addition to a picture of the "dead" switch its wires, please post a picture of the dimmer switch with its wires. – manassehkatz Mar 15 at 21:44
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I had an instance in my current home where the previous owner replaced a three way switch with a non-3-way dimmer and it acted like your situation. The original switch would seem like it did not work, unless the dimmer was on, then it would switch the dimmer.

Take a look at the wires you have and also look at wiring diagrams for a three way light circuit and see if anything makes sense in that context. For my situation, I had to remove three light switches downstairs where the bad dimmer was and figure out what every single wire did until I found the two travelers and hot that were meant for the original three way.

For now, also check your breakers. It's possible that a certain on/off arrangement of your new switches is leading to a short that is tripping the breaker since it doesn't seem like you truly know what wire goes to what screw.

  • Are you saying if we had connected the wrong wire to the common, it should have tripped a breaker? The puzzling thing is 1) it seemed to work fine and 2) we never tripped a breaker. It just stopped working when we shut the power off, put everything back into the box, turned the power back on??? If the hot wire was on the wrong screw.....shouldn’t it have just NOT worked? – Mary Mar 15 at 21:45
  • I guess if it worked at first, the wiring wasn’t bad enough to trip a breaker. My point is, it could have been wired wrong before you started, so step back and look at it with the idea that the dimmer could have been wrong all along. – JPhi1618 Mar 15 at 21:47
  • Agreed. But the problem now is there doesn’t appear to be a hot wire to be found in either box and we can’t figure out why, where it went or how to get it back 🧐 😛 – Mary Mar 15 at 22:26
  • If wires are shorted by accident when you pushed the switches into the wall, another somewhat poor connection before that box could have been damaged before the breaker tripped (or instead of it tripping if it never did). – JPhi1618 Mar 15 at 22:52
  • Ok....that’s what I was wondering. Is it possible to damage/short something somewhere else - (that would only impact that one switch....no other outlet or switch on that breaker) without tripping the breaker. Sounds like it is....ugh. – Mary Mar 15 at 23:39

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