So I am trying to get my new bathroom vent/light/heater installed. I have been up and down in my attic so many times and have had one of the functions working each time, but never all three. I got the heater to turn on and off. I got the light to turn on and off. I got the vent to run, but it would run no matter like there was no switch. I am thoroughly confused at this point. enter image description hereenter image description hereenter image description hereenter image description hereenter image description hereenter image description hereenter image description here

  • Can you post photos of the wiring at the switch box, and post the install instructions as well? Oct 24, 2018 at 4:14
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    Can you replace the cable between switch box and fan? This whole deal would be 10 times easier if you were using /4 cable instead of /2 and /3 cable. Also it would be more legal. Oct 24, 2018 at 6:20
  • Yes, where does power come into this for that matter? Oct 24, 2018 at 11:32
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    They are using the 3 colors in the /3 cable as the 3 switched hots to the fan/light/heater. They are using the neutral in the /2 cable. This is an illegal configuration, you can't send power up one cable and back down another: the current return for each device must be back in the same cable so the currents and magnetic fields in each wire cancel each other out. otherwise you get heating on any nail or strap between the cables (a fair bit due to the high current of the heater) and the cables vibrate due to magnetism, which will fatigue them, causing arcing and fire. Oct 24, 2018 at 18:38
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    Well I guess this is what happens back in 1998 ha. Thank the lord there hasn't been any kind of fire yet, but makes me nervous about how the rest of the house is wired. I am going to fix tonight, thankfully I won't have to get back up in the attic. That would also explain why I could never get the configuration right at the unit. Should have looked at the switch earlier. Live and learn!
    – Jeff Cox
    Oct 24, 2018 at 18:46

2 Answers 2


Hard to tell from the pictures what you currently have. But here is (roughly) what you need.

Updating based on newly posted installation diagram


  • Installing 3 switches in one box Note: I do not know much about how much you can stuff in a box. There are some experts here who can speak to that - when I did this in my own house, my electrician dealt with those details (and many more). I got something like this Decora 15 Amp 3-Rocker Switch which can fit in a single gang box, but be warned that a single gang box is likely not big enough for all these wires (code or practically speaking).
  • Everything on one circuit - i.e., a single 15A or 20A circuit as appropriate based on the requirements of the fan/light/heater - primarily the heater is the determining factor

In the switch box:

  • Cable 1: From the main panel: Black (hot), white (neutral), ground. Hot goes to all three switches. Neutral will connect to neutral from all three devices.
  • Cables 2 & 3: To the devices: Typically 2 cables. One black/white/ground (this is the /2 - 2 wires + ground), one black/red/white/ground (this is the /3 - 3 wires + ground). (Technically this could be done with one bigger cable or with 3 black/white/ground cables or with a bunch of individual wires in conduit, but it looks like you have the typical 2 cables already, so that's good).
  • Connect all the neutral (white) wires together with a wire nut.
  • If your switches have three pairs of screws then connect three short black wires (same size, easiest to just strip a section of Romex and chop off 3 pieces of black wire) together with the black wire from the panel with a wire nut and connect each to one screw. If your switch has a common hot then you connect the hot from the panel directly to it.
  • Connect each colored wire from the cables 2 & 3 to a switch. Two switches get black, one gets red - these are all switched hots.
  • All grounds are connected together.

No white wires to the switch unless it is a smart switch that uses neutral

If your switch has backstab connections and screws always use the screws.

At the fan:

  • Connect the neutrals for the light & fan (whites that are paired with the blue & black wires) to the white in the /3 cable.
  • Connect the neutral for the heat (white that is paired with the red wire) to the white in the /2 cable.
  • Connect the black (fan) wire to the black wire in the /3 cable.
  • Connect the blue (light) wire to the red wire in the /3 cable.
  • Connect the red (heat) wire to the black wire in the /2 cable.
  • Connect all grounds together (as always)

Color-coding: Because the heat uses a lot more power than the light & fan, it gets the /2 cable. Harper recommends (and it is a good idea) marking both ends of the /2 black --> red and both ends of the /3 red --> blue. That will make all the wire colors match, which will help with any future troubleshooting. However, you must make sure that the whites go to the correct (/2 for heat, /3 for fan & light) whites - neutrals & hots must be matched together.

That should leave you with nothing extra hanging out. And you should have each switch operating a separate function in the fan/light/heater.

You also need to vent the fan properly. I had my electrician do that too (not a fun job in my attic). You definitely do NOT want the fan venting into the open area of your attic. If you had another fan before then you may be able to reuse the ductwork and the hole in the roof. If not, that may be the hardest part of the job.

  • So the only thing I don't have connected the way you mentioned is I don't have all the whites (three from unit and two from switch) connected with a nut. I have the heater white connected to one white and then the light and vent white connected to the other. Is this what is causing the issue maybe? I have the switch you referenced above already installed. I am going to check the switch box tomorrow.
    – Jeff Cox
    Oct 24, 2018 at 4:48
  • I got part wrong - each cable neutral gets connected to the neutral(s) of the matching colored wires - that is the white with black/red connects to neutrals of the devices that have their colored wires connected to that black and red. It sounds like you got that part right. Oct 24, 2018 at 4:53
  • So if that is the case then my issue is probably in the switch. I'll take a look tomorrow. What would be the issue in the switch that is causing the fan to just run no matter and none of the switches to work?
    – Jeff Cox
    Oct 24, 2018 at 5:03
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    I fixed it! And it works!!! So happy.
    – Jeff Cox
    Oct 25, 2018 at 1:16
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    I think it was the line to the bedroom in case someone wanted to put a switch on wall right the plugs on the back wall. I got them tied back together and got the new triple switch hooked up and it works like a charm. So happy.
    – Jeff Cox
    Oct 25, 2018 at 2:31

You need some colored electrical tape.

On the /2 cable, on both ends of the cable, mark the black wire with red tape.

On the /3 cable, on both ends of the cable, mark the red wire with blue tape.

In the heater, attach the /2 cable first. Red goes to red (heater hot) and white goes to the heater's white wire which should not be connected to the fan or light's white wire.

In the heater, second, attach the /3 cable to the remaining wires, super simple, same color to same color.

Down in the 3-switch switch box, all the grounds from all cables go together. All the neutrals (whites) go together.

Now one of the cables in the switch box is the supply. That one's hot wire needs to be split 3 ways, e.g. By being wire-nutted to 3 pigtails. You have 3 switches with 2 (non-green) screws each. Each pigtail goes to a different switch, and attaches to one of the screws.

Still unattached are the black, red and blue coming from the fan. 2 of them have been relabeled with tape, use the tape color not the native wire color. Each switch still has a remaining screw unused. That is where those 3 wires go; one per switch.

And you're done.

  • Well the red is in the /3 wire with another black and then there is a black in the /2 wire line.
    – Jeff Cox
    Oct 24, 2018 at 13:26
  • What Harper is saying (and I agree) is to mark the black wire in the /2 red - and from that point on all references to "the red wire" refer to that (formerly black) wire. Similarly, mark the red wire in the /3 blue - and from that point on all references to "the blue wire" refer to that (formerly red) wire. Oct 24, 2018 at 14:04
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    The red won't be in the /3 wire after you mark it blue. Colors in cables are not there to help you, they are there as a necessity of cable manufacture. You can re-mark them to suit your own purposes, and it'll make your life easier if you do, and make it clearer next time you are in there. The one in the /2 cable needs to be red because that /2 needs to power the heater, and red is the color the manufacturer selected for heat. Do it that way, the colors match and it's easy mode. Don't underestimate the value of simplicity when dealing with an octopus like this. Oct 24, 2018 at 14:34
  • That makes sense and I believe that is how I have it connected at the moment. For some reason I think the problem might be in the switch. I am going to check and make sure the switch layout is correct tonight and it may just be time to replace the switch.
    – Jeff Cox
    Oct 24, 2018 at 14:44
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    It almost looks like they hooked up a white as a hot wire instead going up to the unit.
    – Jeff Cox
    Oct 24, 2018 at 18:11

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