I just bought a bathroom fan which needs a seperate wire to control the fan, light, nighlight and humidity control. Each one is designed to be wired to a separate switch, not an ideal design. I'm trying to find a way to control them without switching out to a bigger gang box. I hoped to add the light to my current light circuit, and somehow setup the nightlight to turn on/off inversely with the main lights. So when the main lights are on, the nightlight is off. Any ideas?

Sorry if this has been asked before. In searching I mainly found issues on poorly wired three way switches.

  • The humidity control turns the fan on when it detects humidity. Instead of being wall based, it's on the fan itself. I plan to leave that wired directly to power. It's not that I couldn't use a triple switch - but I want the light to come on with other lights, and the nightlight to come on inversely. Thus the only switch I really want to control individually for the unit is the fan on/off.
    – Steven
    May 23, 2016 at 16:34

1 Answer 1


A three-way, or single pole double throw (SPDT), switch should be able to do what you want.

  • Connect the ungrounded (hot) line feeding the switch, to the common terminal on the three-way switch.
  • Connect the ungrounded (hot) line feeding the main light, to one of the switched terminals on the three-way switch.
  • Connect the ungrounded (hot) line feeding the nightlight, to the other switched terminal on the three-way switch.
  • Connect the grounded (neutral) line feeding the switch, to the grounded (neutral) feeding the lights.
  • Connect all the grounding conductors together, including a ground to the switch and the box (if it's metal).

When the switch is in one position, the main light will be on. When the switch is toggled the other way, the night light will be on.

Crappy drawing of three-way controlling two lights.
Crappy diagram of three-way controlling two lights

  • Thanks! I wasn't sure you could use a three way switch this way.
    – Steven
    May 23, 2016 at 16:36

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