Box and old switch

I’m trying to replace a light switch that has 2(Red & Black) wires directly connected to the switch itself with a 3rd(White) wire that’s capped off in the box with a new smart switch that has 4(Red- Load out, Black- Line, White- Neutral, & Green- Ground)wires. Is the white in the box neutral? The old light switch has a ground screw and the white wires aren’t connected to it so I think they’re neutral. And if that’s the case what do I do with the ground wire from the new switch? Do I connect it to the screen in the back on the box? Help. Thanks!!! old switch showing ground screw new smart switch

Is this screw for grounding the green wire from new switch? enter image description here

  • Can you post your last photo, sans the red circle, please? I can't quite tell if that's BX back there, or what Commented Feb 20, 2020 at 2:59

2 Answers 2


You do not attach the green wire because there is nowhere obvious to attach it to, and you don't really need it. The switch will ground through the mounting screws. (note switches can do this; receptacles cannot).

The screw you circled is not a grounding screw; it is a cable clamp, and you're not allowed to use it to attach grounds. You notice several holes in the back of the box; it's possible one of those is tapped #10-32, and if it is, that is for a ground screw. Any #10-32 screw will do, but they sell green ones just for this task.

Typically, wire colors in switch are an insane nightmare of contradictions. Especially if a 3-way is involved. However, in this particular box, the native wire colors happen to perfectly match the preferred colors for their functions. So in this box, this one time, you do indeed match black to black, red to red and white to white.

  • Thank you so much Harper. You guys really helped. Will try this tomorrow. 🙏🏽
    – Jay D
    Commented Feb 20, 2020 at 6:56

The black wire from the box, old switch, gets connected to the black wire from your new switch with a wire nut. The red wire from your old switch gets connected to the red wire from your new switch with a wire nut. The white from your new switch gets connected to the group of white wires under the yellow wire nut, those are the neutrals. I can't tell if there's a ground wire in the box from the cables or if it's FMC. Verify the box is grounded with a meter going from box to black (hot).

  • Jack: Think you are mostly right, but wanted to ask one more thing: It looks like 3 blacks on the red wire nut one of which ends being an unswitched black on the /3 cable. Is this going to a ceiling fan with a remote or local switch? In either case, Jack is right, I was just curious. Commented Feb 19, 2020 at 22:54
  • @GeorgeAnderson It could be going anywhere, vanity lights, outlet, a fan like you mentioned.etc. Only the shadow knows .... (and the OP)
    – JACK
    Commented Feb 19, 2020 at 23:21
  • I think Jack is 100% right
    – Ed Beal
    Commented Feb 19, 2020 at 23:26
  • 1
    Don't need to hook up the ground wire, if the box is grounded it'll pick it up through the mounting screws. On switches. Commented Feb 20, 2020 at 1:01
  • @Jack there’s a total of 3 black under that cap, the one from the switch and the two coming out the wall. There’s also 2 white under the yellow cap. It’s going to a regular light bulb, just 1 bulb fixture in a bedroom. First time doing this, I did turn off the breaker for the room 😬 @ Harper so just leave the green ground wire hanging there?
    – Jay D
    Commented Feb 20, 2020 at 1:30

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