My kitchen had 2 existing 3-way switches to control the main kitchen light. These three-way switches functioned as expected -- either one would turn the light on or off.

When I decided to replace one of the switches with a 3-way dimmer switch, I discovered that my wiring appears to be non-standard. The new 3-way dimmer switch has 2 red wires and 1 black wire, which appears standard. However, the existing house wiring for each switch has 2 black wires and 1 red wire.

How can I hook up this new dimmer switch to my existing wiring? My house is in the US and was built in 1998, if that matters.

  • Implying there even is a standard for 3-way wiring lol... there isn't... it's all a mess, and the most novice-unfriendly thing in all of wiring. Colors in particular are nearly 100% randomized, and so are screw positions on switches. Mar 7, 2022 at 19:32

1 Answer 1


On the switch you want to replace, look for the black screw. That will be your common terminal. The other two wires on that switch will be your travelers and should be connected to the two red wires on your new dimmer. The wire connected to that black screw on the old switch needs to be connected to the black wire from the dimmer. Remember to turn off all power before working on anything.

There is nothing non standard with your wiring, just different color wire for the same things.

  • 3
    Remember: Electricity doesn't care what color the insulation around the wire is.
    – FreeMan
    Mar 7, 2022 at 15:10

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