I have a bathroom on my main floor with three switches: lights, fan and heat lamp. I am replacing the fan and do not need the heat lamp, however when I wired the two switches I want to use, the white wire on the fan side is hot and blew the circuit. I disconnected it, and now the lights do not work and the bathroom fan UPSTAIRS is not working. I really do not want to rewire my bathrooms, does anyone know why they would be wired this way? How can I keep the existing wiring and get my fans working? Thanks, enter image description here

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    Can you post photos of the insides of the boxes involved? Commented May 21, 2019 at 1:57
  • Miles, I am off to bed now, but can update tomorrow. I wired in the switch on the left (black from power to switch, black up into wall from switch and white from "power in" source and directly up into wall). Now the upstairs bathroom fan works if this is switched on.
    – R Sale
    Commented May 21, 2019 at 3:40

2 Answers 2


If you're asking why are both on 1 circuit, that's because they can be. A bathroom circuit for lighting can cover all lighting in both bathrooms that do NOT include a heater. A 3-in-1 fan, heat, and light must have its own dedicated circuit, however.

Here are some relevant questions to answer regarding this requirement:

  1. What gauge wire is being used?
  2. What size breaker is it?
  3. Have you tested the lines with the breaker off to verify that all lines are dead?
  4. How certain are you of which lines are main supply lines?

Lines cannot be randomly spliced in the walls like your diagram suggests. I would personally use a 12/3 and use the 3rd hot line as a bypass through the switch, lights, and to the next switch. So what you think is upstream could be downstream.

Testing would entail

  1. disconnecting all lines
  2. safely capping them
  3. turning on the breaker
  4. testing the lines
  5. turning off the breaker
  6. connecting the verified hot line to the next line directly and capping them
  7. turning on the breaker
  8. testing all lines to verify what line is what and that they aren't spliced randomly
  9. repeat till you have a definite, complete diagram

I also recommend cleaning up the diagram showing power in, number of lines, and where you want things. The "what was" and "what will be" part makes it hard to follow.

  • You are correct Robert some of the switches are on the same circuit. I found this posting as well link. Upon further testing, the switch on the left (#1) controls the fan and it also feeds the power to the fan in the bathroom upstairs. Switch # 2 is not being used now. On switch #3 (now the light) the power in comes from the top, and is actually on a different breaker. All 12 gauge wire, both on 15 amp circuits. I am marking your response as answered.
    – R Sale
    Commented May 21, 2019 at 13:23
  • I just had lots of fun wiring my house... jokes... sorry about the typos. I was at work and rushing. If you need any help, let me know what lines are main feed and how many are in each box. I can sketch a diagram based on that. May take a couple times, but it's not hard. Just need a picture to follow.
    – Robert
    Commented May 21, 2019 at 14:19

It sounds like the fan or light may have the switch on the neutral side of the load, not the hot side, and when you connected the neutral you got a short and possibly melted a connection or burned out a back stab connection on a switch or outlet.

  • Or, that white wire may be switched hot (on switch loop) rather than neutral. Neutral is always white, white is not always neutral. This is why one of the first questions we always is is "can you show us a photo of the inside of the box, preferably with everything connected the way it was before you started trying to change it"; wire colors are not enough.
    – keshlam
    Commented May 28, 2023 at 23:40

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