Update: I think one of the black/white cable pairs is for the thermostat. One of the neutrals/whites is not being used, and that's probably for the thermostat.

Here is a picture of my wire box that I made. I'm guessing the right is source and the two to the left are the light and the outlet that is controlled by the switch. I have two insteon switches that have a red, black, white and green/ground wire.

When I opened it up, there seemed to be a lot of extra connections/wires, so I removed two of the connections/wires. I didn't take a picture, and I don't remember how it was configured! The middle neutral wasn't used, the two blacks on the right were together, one red and one black were connected, etc. Now I just want to get to a point where I can use my switches and not have something catch on fire!


  • 1
    "there seemed to me a lot of extra connections/wires, so I removed them" <- good luck ...
    – brhans
    Commented Sep 26, 2016 at 20:27
  • 2
    What was there before, and what was each switch controlling? Did any of the switches have 3 wires connected (or switched a light that can be controlled from another switch somewhere else)? Do you have a multimeter (because we'll need that to check voltage and figure out what is going on)?
    – gregmac
    Commented Sep 27, 2016 at 3:05
  • 2
    I'm still very confused on your setup. The "mystery switch" is a 3rd switch, in addition to the two dimmers? With everything disconnected, there are outlets that aren't working? You also mentioned switched outlet in the question: was there previously some outlets where the top (or bottom) was switched, and the other side was constant? And now those don't work at all?
    – gregmac
    Commented Sep 28, 2016 at 13:29
  • 2
    The next step is to figure out where power is. Disconnect all the wires, put a wire nut on each, then turn the power on. Very carefully, using your multimeter, test for AC voltage (VAC) between each wire and ground (the metal box). Leave the wire nut on, just insert the multimeter probe inside the nut (remember: at least one of these wires is now live!). There should be ~120V between one of the black wires and ground: that is your incoming power. There should also be 120V between the white wire in the same cable, and 0V between that black and everything else.
    – gregmac
    Commented Sep 28, 2016 at 13:32
  • 1
    You can figure out how the outlets are connected also using your multimeter. Turn all power off and disconnect everything from the outlets. Change your multimeter to measure resistance (Ohms Ω) and measure between white/black and white/red. You should get infinite/open loop (∞ or "0L" "OL" or "1. "). Plug in a light with an incandescent bulb in it, and measure again. You should get something in the 100-300Ω range on whatever connects to the receptacle you plugged into. Check both the top and bottom half of receptacles: I suspect you'll find the red wire was used for a switched outlet.
    – gregmac
    Commented Sep 28, 2016 at 14:12

1 Answer 1


It could be worse

Copper thieves could have taken a bunch of wires, leaving you no idea how things were ever hooked up.

So you have to get your multimeter and start testing stuff, and some of this must be done hot. Figure out which wires are your power supply. Figure out which breaker it is on. Bonus points if you slap a GFCI breaker there to keep you honest. Make sure it doesn't trip before you start.

Then you have to move through each group of wires and figure out what they do. I wouldn't throw power on any lines until I have made sure they are not a switch, by checking for resistance with switch(es) in all positions.

Hook up the grounds first, in any case.

Having a few incandescent bulbs and dollar store night lights helps a lot.

One of my most useful tools for that is an appliance cord and two wire nuts. If you have a pair that reads infinity ohms until you plug in a nightlight or install a lamp bulb, splice their hot and neutral into the cord, plug in to a supply (fed off another circuit of course) and see what else lights up.

Work through it, labeling or diagraming as you go.

It really helps if you know how to do electrical wiring. If you don't, you won't know what you're looking at. For instance, that 3-wire bundle black/white/red probably has something else going on.

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