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I am in the process of updating some light switches in my home and I encountered a single pole light switch with 4 wires attached to it. It is the light switch on the right in the diagram.

This light switch is inside a bathroom and these two switches control a fan / light combo, and vanity lights. The switch on the right controls the vanity lights and the fan, so I assume that is why there are two wires attached to the top (B4 / B3).

B2 is the hot wire and it loops around the screw and jumps to the switch on the left.

B1 is a wire that comes from the box and is backstabbed into the light switch. I tried removing it from the light switch and the outlet inside the bathroom lost power. I assume that they are just using the light switch to make the wire hot instead of adding it into the wire nut?

Would the fix for this to add B1 to the pigtail with the black wires?

Thank you in advance for your help.

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  • It looks like they just used shared terminals on the switch to avoid a more complicated pigtail -- that is, unswitched power from B2 is being passed through and to the outlet rather than having B1 connected at the wire nut, and similarly using the upper terminals for B3 and B4 rather than having one pigtail hack to a wire nut connection that feeds both of these.
    – keshlam
    Apr 10 at 21:01
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    For Pete's sake, don't grab a diagram that doesn't correspond to your switch, and then stick wires on random nonexistent screw terminals when you don't know what to do with them on the drawing. Draw it like it is or don't draw it.
    – Harper - Reinstate Monica
    Apr 11 at 0:43
  • I apologize, I did use the incorrect diagram, I do have a single pole switch. Thank you for making those edits for me. @Harper-ReinstateMonica.
    – chize
    Apr 12 at 16:27

2 Answers 2

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The switch drawing is for 4-way switches - 2 screws on each side plus a ground screw. But based on your description and what I can see of the actual pictures, you have simple single-pole switches. Based on that, the previous installer used backstabs and loops instead of pigtails and wire nuts.

Incoming Hot

  • Replace B2 with two separate pigtails, one to each switch
  • Connect the two pigtails and B1 to the wire nut. If the nut is not big enough or seems worn out in any way, use a new wire nut.

Switched Hot

  • B5 = one light
  • B3 = the other light or the fan
  • B4 = the other light or the fan

You should be able to separate B3 and B4 to use on two separate switches. In fact, you could even put in a triple switch like this Leviton from Home Depot:

Leviton switch

and if you do that then B3, B4 and B5 all go on one side and you only need one pigtail for B2 instead of 2. That would also leave a space in the box, which could be filled with a duplex receptacle, but since it is in a bathroom you need to make sure it is GFCI-protected.

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    Thank you for your detailed explanation and yes you're right, my switches are single pole switches I used the incorrect diagram I apologize for that! I went ahead and did the changed you suggested and everything works!
    – chize
    Apr 12 at 16:26
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That connection on the back where the wire just disappears, is called a backstab. That is internally connected to the nearest screw. In this case, it is lazily being used as a splice. Very typical, nothing particularly wrong with it except backstabs are unreliable, so best avoided.

So, your right switch has B1, B2, the wire nut and the inter-switch jumper all connected to each other (and obviously to the switch terminal as well). We can surmise that this is "always-hot" from the supply, since so many things are interested in it. It's very typical for this to be a wirenut pigtail, and yeah, you have one, so feel free to use it more. If you add enough wires to it, you may want to go to a red or tan wire nut, which holds more wires.

The B3 and B4 are connected to each other. Being on the other terminal of the switch, they must be switched-hot. There being two of them, they must go to different places, so you have 2 separate things controlled by this same switch.

The red wire is obviously in a /3 cable with a black wire. It wouldn't be the other switched-hot wire on this switch, because that would be pointless.

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