I have a system in my bathroom that was causing a flicker in one of my lights, so I investigated and found a wiring setup that I was unfamiliar with, so I thought that it was the cause of the problem. I think it was the problem because with some modifications, the light stopped flickering. However, now I have a burning/fishy smell, and I had to remove part of the system from two 2-gangs to one 2-gang, and I can use one of my lights and my bathroom fan.

The system

I have two 2-gang boxes on the same 15A circuit. One 2-gang has source in/through and is two switches for 3 lights (a single and a pair of pot lights). The power then continues to charge the other box, and this is where the fun begins.

Originally, the power continued through the first box and went up to a ceiling light that functioned as a junction box where some complicated wiring lead to two cables that were charged going to box and powering the switch. There were only two cables, and not 3, for the two switches, so no source specific cable going there.

I changed it by adding a source cable from the passthrough of the first 2-gang. Now the second 2-gang has 3 cables going in. This is when I got a strong fishy smell.

So, I am wondering what my problem might be. I was thinking that it might be because I have two boxes that are internally wired in parallel that are powered in series. So, I was thinking of passing the source from the first box directly through without powering the first box, running it to a junction box, and then powering both 2-gangs from there directly. But before I potentially cause a fire or damage more switches, I thought I would ask around for advice.

Thanks for any suggestions or insight!

Proposed fix

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  • 2
    Burning/fishy smell means something causing the smell must be replaced, now. Flickering usually caused by a loose connection. Should turn off the breaker before a fire starts.
    – crip659
    Commented Oct 30, 2023 at 16:02
  • 1
    Your use of the expression "2-gang" doesn't actually say what's in the boxes. "Gang" means one space for a screwed-in device (switch, regular outlet, GFCI outlet, etc) to be installed in. So one doesn't power a "2-gang". Instead, one runs power to the devices inside the box. Maybe describing more what is in each "2-gang" box might help the answerers? Commented Oct 30, 2023 at 16:12
  • 2
    Also, rather than drawing wire up to the box, please show the wiring inside each box, as it goes to each device. Maybe pictures of each box's contents might help? Commented Oct 30, 2023 at 16:13
  • 1
    So you went from a flicker to burning/fishy smell. That's not an improvement. That's one step closer to burning your house down. This may not be the best place for you to DIY, without a LOT of self-education first.
    – Ecnerwal
    Commented Oct 30, 2023 at 16:37
  • 1
    Actual pictures of the actual wiring in each of the boxes involved. Also, the "before" pictures that you took of all this. What's that? You didn't take before pictures? Lesson learned... ;)
    – FreeMan
    Commented Oct 30, 2023 at 16:48

1 Answer 1


As drawn in the "Existing" drawing, cropped here: "existing" wiring this wiring is correct.

Power comes into the first box with two switches, then taps off to go to the second box with two switches. White wires all connected together in each box. Ground wires are connected together in each box. White and ground are not cross-connected.

The added junction box and third wire you have added are not necessary. (Note, though, that if you have already broken the pass-through wire with the junction box and the third wire, the junction box needs to stay, and must be accessible from the room with a proper cover placed on it, not buried in the wall. Or replace the broken pass-through wire with a new complete wire, then no junction box needed.)

Try to duplicate again what is the "existing" setup drawn above, and you should be back in business.

The original flickering may have been caused by a poor connection in the wire nuts, the switch screws to that light, the light fixture connections, the spring tab inside the light fixture to the bulb not being springy enough, or an old LED light that is about to go.

  • thanks! The existing is what I wired up to get rid of the funky wiring that existed previously, and it is what originally gave me that fishy smell. I wasn't sure that passing through a source to the second box may have been the problem or not. For the flickering, I had changed the connectors, switch, lightbulb, and even fixture to track down the issue, and so the only thing I could think of was the wiring. No other lights flickered on the circuit. When you say cross connected, do you mean the switches wire inversely? Commented Oct 30, 2023 at 17:19
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    "Cross-connected" was referring to the white (neutral) and ground wires. Switches never go on neutral or ground. Neutral and ground are also never connected together (cross-connected), except in the main breaker panel. It is OK, however, to pass through the white (neutral) and ground wires along from the first box to the second, along with the power (black). (Assuming USA coloring) Commented Oct 30, 2023 at 17:34

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