I have a light switch that is connected to a power outlet. The light switch has 2 block wires, one coming from the wire and one coming from the power outlet.

I want to change this to a dimmer and I think i need to connect the top wire to the black dimmer wire and the bottom to the red dimmer wire, then connect the green to my existing earth.

Note: The switch controls wall lights Outlet is always on, switch does not control it.

I should mention, this is in the bathroom, so should I also replace the outlet with a GFCI ? enter image description here

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  • Just to let you know, I believe that it is against code to power an outlet through a dimmer. Also, a GFCI outlet is unlikely to work correctly when powered through a dimmer.
    – DoxyLover
    Feb 8, 2018 at 19:56
  • I haven't made any changes yet, considering getting an electrician.
    – Gribbler
    Feb 8, 2018 at 20:13
  • @DoxyLover I don't think OP plans to, I think the plan is to feed switch/lamp pair from power which serves a receptacle first, grabbing hot/neutral off that receptacle. OP interesting note, your box is installed flush to the wall (not inset) - which means you can ground your switches and receptacles simply by screwing them down hard flush. But only if you remove the little squares that capture the screws! Feb 8, 2018 at 20:42
  • I agree with @Harper, I guess the question is, does this switch control the receptacle or some other device?
    – Jeff Cates
    Feb 8, 2018 at 21:21
  • 1
    The switch controls a light fixture (which I want to have a dimmer for instead of the switch), i tested the outlet and it does not control that , it's always on. There is no GFCI in the rest of the house.
    – Gribbler
    Feb 9, 2018 at 0:45

1 Answer 1


Yes, go ahead and replace the receptacle with a GFCI receptacle

Your idea of replacing this receptacle with a GFCI is a good call, considering that Code has required GFCIs in bathrooms for a good few decades now. You'll want to remove the current pigtail since your dimmer has wire leads, by the way. Also, leave the sticker on the GFCI's LOAD terminals since you have no use for them here.

Once that's done, the dimmer is easy

The dimmer's black lead gets bundled in with the always-hot coming into the receptacle (you may need to pigtail the receptacle's hot for this), the black wire going out to the cable to the light gets connected to the red wire on the dimmer, and the dimmer's green wire gets bundled in with the grounds in the box.

  • You might check the circuit breaker feeding this circuit on the odd chance that it is GFCI. It would be marked as such and have a button marked "test". Most likely it's not there and you should just install a GFCI outlet.
    – Stanwood
    Feb 9, 2018 at 3:24
  • If the outlet is always on, would it make sense that the feed is coming from the bottom left corner, and the wire going to the light would be the top right?
    – Gribbler
    Feb 10, 2018 at 1:58
  • @Gribbler -- assuming you're speaking about the switch, then yes, you are dead on :) Feb 10, 2018 at 2:42
  • All done! Thanks so much for you help, It was pretty straight forward once you explained it, i think the bit that confused me initially was thinking in the hot wire was going into the switch first then the outlet, when it was in fact the other way around.
    – Gribbler
    Feb 11, 2018 at 0:01

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