I'm looking for feedback on how to wire a second light from an existing wall switch. I am providing a self-drawn diagram and an actual photo of the existing box with the wires exposed in an attempt to express myself as clearly as possible.

Here is my drawing. I'm sorry it's not the best. I can redo it if it appears too poorly done. enter image description here

I actually think a real photo in its current appearance is harder to make out what's what: enter image description here

So here are the details. The areas of each corner marked "A", "B", "C" and "D" are actual Romex wires that enter the box from each corner. This will be a two gang junction box, by the way. One will control the existing ceiling fan and the other will be a dimmer for the new lights. Currently, the "A" Romex leads up into the ceiling and powers a ceiling fan. Romex "B" will power the new lights which will have a total of four LED flush-mount lights in the corners of the ceiling. Total wattage for all four will be 28w. The ceiling fan has a total of 57w (that's at the highest settings for both the light and fan speed). Romex "C" (I'm 98% certain) is the power from the circuit box. And Romex "D" is a line that runs to the bathroom. I know that bathrooms should have their own circuit. I didn't wire it that way. That's just how I found it. I can't change that.

What I am looking to learn is how to connect Romex "B" (the new light) correctly. I tried connecting a dimmer switch for my new lights by connecting the the hot wire from Romex "B" to the black shared wires "A" and "D". Then I tried to connect the neutral white wire from Romex "B" to the neutral white shared wires from Romex "A", "C" and "D." This blew the circuit and I fried my dimmer switch.

I think my error was that I connected incorrectly to Romex "D" as and now I'm pretty sure that wire goes to the bathroom (hence why I mentioned I'm 98% certain above). Romex wires "C" and "D" are either one or the other (either power from circuit breaker box or a line to power the bathroom).

Do I connect the Romex "B" hot to the hot on Romex "C" and Romex "B" white neutral to Romex "A", "C" and "D"? I am confused.

  • Are you sure you're describing that correctly? Based on what you said about hooking up the dimmer, you did not hook up the dimmer at all. You hooked B white to the neutral bundle (correct) and B black to the 3-black bundle, which should have made the light turn on continuously. No mention of any dimmer. Is the dimmer in a different junction box? Jan 10, 2020 at 10:36
  • I connected the neutral wire of the dimmer to the neutral bundle. And then I connected the hot or black wire of the dimmer to the black wires from Romex "A" and "D" which also is the top wire that has a wire nut that connects to the ceiling fan control in my drawing. Having those connections is what blew my dimmer out. It's fried.
    – Adrien
    Jan 10, 2020 at 11:08
  • What loads in the bathroom does run D power? Jan 11, 2020 at 0:29

1 Answer 1


It sounds like you connected the dimmer to the fan speed control output. Don't do that.

In fact, just go ahead and bypass the dimmer and wire it cable B neutral to neutral bundle and cable B black to the bundle you think is "always-hot". This will make the light go on 24x7. Then, operate the fan speed control and see if the lights are affected, If they are, you got the wrong black bundle. Switch.

Once you're sure of the black wire, then install the dimmer.

  • Just to be clear, the existing white neutral bundle has three wires. So do I attach a neutral white pigtail from my basic light switch and the white neutral wire that is running to the new lights in the ceiling all to the same bundle? This would make it a total of five white wires all bundled together.
    – Adrien
    Jan 10, 2020 at 22:15
  • Also, I turned the power off and disconnected all cables, then turned the power on and learned that Romex "B" black hot is power source from the breaker. So at least now I know where the power is coming from.
    – Adrien
    Jan 10, 2020 at 22:16
  • Update: I pigtailed a 6" black wire from my basic single pole switch to the black "B" bundle that is always hot and then I used another 6" white pigtail for neutral to connect to the white bundle (for a total of five wires) and it keeps blowing the circuit. It did not work.
    – Adrien
    Jan 10, 2020 at 22:36
  • Not sure if this will show up as an image but I found out how to make it work by following this diagram: do-it-yourself-help.com/images/…
    – Adrien
    Jan 10, 2020 at 23:02
  • 1
    No, you would never connect a neutral to a plain switch. Are you just randomly trying things? Never do that - you can stumble upon a combination that "works", decide you are done, and that way has a safety issue that will kill you. Far less experimentation, far more research, please. Jan 11, 2020 at 2:03

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