I have two existing dining room lights that are controlled via a three switch.

The existing wiring has two switch locations:

  • Box 1 (garage)
    • One 12-2 romex (black to black terminal on 3-way)
    • One 12-3 romex (black and red on travelers, white wire nutted to white on 12-2)
  • Box 2 (Hallway)
    • One 12-3 romex (black and red on travelers, white on black -- not marked as hot)

I assumed then that the feeder was coming into box 1. I ran a new 12-2, pull the old box, put in a 2 gang box, and added my new single pole switch.

I removed the black wire (Original 12-2) and made pigtails, landing one back on the 3-way black terminal (where I pulled it), and landing one onto the bottom terminal of my new single pole switch.

I add the white from my new 12-2 into the wire nut of the old 12-2 + 12-3 to carry the neutral to the new light. The black from the new 12-2 I land on top of the single pole switch.

To wire in the new light, I removed the old light and removed the pigtails it had to the neutral in the box, and old hot from the 3-way switch. I pulled my new 12-2 from box-1 into this ceiling box and wired the new light directly to its black and white.

When I test the 3-way, the single light remaining on it works as intended. The new single pole switch however, does nothing. Then I notice, if I flip the 3-way to the "off" position (no power through the 3-way to the light) the single pole switch works.

I pulled my switches from box-1 and and checked the existing 12-2 with my meter, it has 120vac on it at all times (regardless of what position I put either 3 way in). I land that "hot" wire directly on my single pole switch and it works as intended. The moment I take a jumper from and touch it to the 3-way, the single pole switch stops working.

I'm at a loss for other things to try for troubleshooting. Any ideas / thoughts would be helpful.


Box 1 (Garage) Box 1 wiring

Box 2 (Hallway) Box 2 wiring

  • 1
    Can you post photos of the insides of the boxes please? Also, can we presume that this is an attached garage? Commented Nov 21, 2023 at 3:39
  • Will get some photos together (though doing this from desktop, might take me a minute to figure out how to attach). It is an attached garage, but the garage being there is kind of misleading. I was just using that as a location reference. Really its just near the garage door, the other switch is in the Hallway.
    – Leif
    Commented Nov 21, 2023 at 3:56


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