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.