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I have a light switch that has one conductor cable going into it (black & white).

This goes to a double outlet (top switch controlled) with 3 conductor cables running into it. Two from the top holes and one from the bottom hole. The top outlet of the two has white wires either side and the bottom outlet just has a single black wire. However there are a bunch of wires nutted together. (4 black & 3 white)

I want to add a light to the switch and make the top outlet permanent hot.

I have rewired the cable going from the switch to the outlet and wired in the ceiling light. I attached the switch white wire to the black wire coming from the outlet. I then attached the black wire from the switch to the light and finally the white wire from the light to the white wire from the outlet.

This works, but only when I complete the circuit by plugging something into the switch controlled outlet.

Have I rewired this correctly so far, if not what should I change? How do I make the outlet permanent?

enter image description here enter image description here

Existing wiring before updates:

Existing wiring before modifications

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  • Key question: Where does the cable from the ceiling light go, to the switch box or to the receptacle box? Nov 19 '21 at 13:24
  • The white wire from the receptacle goes to the light and the black wire from the switch goes to the light.
    – Rob Fyffe
    Nov 19 '21 at 17:49
  • You should never have one wire by itself. Based on the pictures, your wires are in cables. Is there a cable from switch to light or from receptacle to light? Nov 19 '21 at 17:57
  • Ok so originally there was one cable from switch to receptacle (3 internal wires). I split this single cable to tap in the ceiling light (essentially now two separate wires). I put the black wire from this switch cable into the light. Then I joined the other white wire from the switch cable to the black wire going to the receptacle. The remaining black switch wire goes into the light. It now essentially is the same as this: youtu.be/CaaLw01fMo8?t=198
    – Rob Fyffe
    Nov 19 '21 at 18:15
  • Did you literally "split" it - i.e., take the black and white out of the outer sheath (beyond the few inches that is inside each junction box, that is)? Nov 19 '21 at 18:28
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You can't "split cables". All wiring must be grouped (minimum pair hot/neutral or switched hot/neutral, but sometimes three = hot/travelers or switched hot/travelers etc.). This isn't just to keep track of things, though it does help with that. It is because of the way electricity (alternating current) works. The end result is either cables (2 or 3 or more wires together inside one outer sheath) or conduit (metal or plastic tubes with individual wires inside them. You have cables, and switching to conduit generally doesn't make sense, so stick with cables. But except for getting small pieces to use as pigtails inside junction boxes, you can't use wires from cables outside of a completely assembled cable.

Numbering of wires in cables normally excludes the ground wires. Ground wires are either green or bare. Simply put, ground goes everywhere, all grounds connect together and all devices connect to ground (through a screw, a captive wire or through a metal yoke on a metal box). So the following explanation ignores grounds, and some references in the question/comments to "3 wires" were, I am pretty sure, really what are referred to as "/2" cables = black + white + ground.

Now on the specific problem.

You have a classic switch loop. Confusing when I first learned about them, but not too hard in the end. A switch loop (historically, now a little different with neutral required in switch boxes) with standard cables uses black for switched hot and white (which is normally neutral) for hot. It didn't use white for neutral because the cable only had two wires and a simple switch doesn't need neutral. Actually, based on your diagram, your original switch cable may have been backwards, but it doesn't matter.

You have a duplex receptacle with the top controlled by the switch and the bottom not switched.

You have an incoming (from the panel or previous devices) hot/neutral cable.

You have one additional cable, going on to other places.

The key here is figuring out which cable is the switch cable. Based on your diagram, it appears to be the bottom cable. There are ways to figure it out for sure, but I am assuming that you are 100% certain which cable is the switch cable. So here is what you need to do:

In the receptacle box:

  • All 3 cables should have their blacks together with a wire nut. This is the hot bunch.
  • All 3 cables should have their neutrals together with a wire nut. This is the neutral bunch.
  • A pigtail (short white wire) from the neutral bunch to a silver screw (long slot, left side if you are looking at the front). This side should still have a metal tab connecting the two screws.
  • Two pigtails (short black wire) from the hot bunch to the top and bottom brass (short slot, right side) screws. This is critical because the tab was removed from the hot side during the original installation. Alternatively, you could install a new duplex receptacle and then only need one wire on the hot side.

In the switch box:

Assumption: you are using an ordinary (not: smart, timer, motion detector, dimmer, etc.) switch. If you are using any of those then neutral needs to be connected.

YOU MUST RUN A NEW 2-WIRE CABLE FROM THE SWITCH BOX TO THE LIGHT FIXTURE.

IF YOU ACTUALLY CUT UP THE EXISTING CABLE, YOU MUST RUN A NEW 2-WIRE CABLE BETWEEN THE RECEPTACLE BOX AND THE SWITCH BOX.

  • Black from old cable goes to one switch screw.
  • White from old cable is connected to the new cable white.
  • Black from the new cable goes to the other switch screw.

In the light fixture box:

  • Black from the new cable goes to the hot screw or black (or red or blue, but usually black) wire.
  • White from the new cable goes to the neutral screw or white wire.

Sorry, you will need a new cable between switch and light. That may result in some drywall work, depending on accessibility. In my house it was done (not by me) in 3 rooms without any drywall work, but it helped that the ceiling is accessible in the (otherwise useless) attic.

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  • Thanks for the extremely detailed response. I am confused about the new cable maybe I described it incorrectly. I have essentially cut the cable that goes from the switch to the receptacle into two cables. Would adding a new cable not be doing the same thing? I essentially have two cables now. One from switch to light and one from light to outlet.
    – Rob Fyffe
    Nov 19 '21 at 19:55
  • If that's what you have, it's fine. What you can't do is pull black and white from a cable to run them separately. But how did a cable from receptacle to switch become long enough for receptacle to switch and switch to light? Nov 19 '21 at 20:09
  • hmmm ok I see, I did join the black and white separately. The reason being how would the switch control the light then since the light is first on the circuit? It would always be on if the power doesn't go to the switch first, right? Regarding length I extended the cable using wire nuts in a separate electrical box.
    – Rob Fyffe
    Nov 19 '21 at 21:00
  • Further update. I updated the receptacle like how you described and everything is working correctly, Switch, ceiling light and outlet. However, I am concerned by the fact you said not to join black & white separately outside of light.
    – Rob Fyffe
    Nov 19 '21 at 21:43
  • From doing some research I have found plenty of examples with no mention of being bad. This is basically what I have done: i.stack.imgur.com/0S156.jpg
    – Rob Fyffe
    Nov 19 '21 at 23:12
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This is a case for re-marking wire colors to indicate function

There's a lot of subtle stuff going on here, along with a blatant mis-wiring/Code violation regarding wire markings.

However, this thing would be dog-simple if you could just visualize it. I'm a huge fan of using wire colors for that, and the key to that is using colored electrical tape to re-mark wires. Whenever you re-mark a wire, mark both ends of the wire the same.

enter image description here

In this type of installation, wire markings are largely not required by Code - Code expects a licensed electrician will recognize from experience what's going on. But as an empowering feature for novices, I recommend optional markings. And use the quasi-standard colors:

  • White = neutral (Code mandatory in any case)
  • Black = always-hot - hot at all times (except power outages)
  • Red = switched-hot - hot when lamp is desired to be on

Decoding the switch loop

The first rule is in AC mains electrical, we switch (interrupt) the hot side, not the neutral side, for safety.

You can search "switch loops" for the full details, but switch loops commonly use the standard black-white cable, causing the native colors to be illegal (white that is not neutral). Thus, remarking is required.

  • Code requires two things: a) that white be used for always-hot (to make it more obvious that it's not neutral), and b) that it be re-marked with black or colored tape to indicate it is not neutral. Since we are obliged to use it for "always-hot", I advise black tape.
  • The black wire, therefore, must be "switched-hot". It's legal to leave it black, but for clarity's sake I advise marking that with red tape so it's obvious what that wire does.

Decoding the split receptacle

A "split receptacle" like this has its sockets under independent control. You notice the top and bottom of the socket each have a screw. Between them is a metal "tab" which can be broken off. Not broken off, the 2 screws are a handy splice. Broken off, they provide separate control.

Since we switch hot and not neutral, 98% of the time you want to leave the neutral tab alone. That side will be all neutral.

We want one socket "switched-hot" and the other "always-hot" so you break off the tab on the hot side; one gets a red wire, the other black.

The remaining two cables (marked ?), seem too be simply always-hot and neutral. One is coming from the panel, the other is going onward to supply other points-of-use. That is typical. Their native colors match up to our color code, so they can be left alone.

Now with things marked, you can see how the original wiring made sense - except the switch loop wires were illegally reversed (white for switched-hot) and not properly marked. This can be corrected at the socket end; there's no need to change anything at the switch end, since on a plain switch, the terminals are interchangeable.

enter image description here

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