I’m trying to install a Lutron Maestro fan/light dimmer, but it turns out the wires in the switch box don’t seem to do what I expected. Currently, the fan and its lights can be turned off completely by a single switch on the wall, and there are also pull chains to separately turn the lights and/or fan on/off when the switch is on. The switch box is wired like this:

switch box wiring diagram

Originally, I thought that this could work because there are two black wires (joined together) and a red one, so three in total. However, it seems that the two black wires actually must be joined for the circuit to work – if I separate them, neither the fan and its lights nor the lights in the adjacent room turn on anymore.

Does that mean that I can’t control the fan and its lights separately after all? If so, why would one of the wires be red instead of black?

This is in Canada (Ontario) in a townhouse built in the early 1980s, if that matters.

  • probably not. what is in the junction box behind the fan?
    – Jasen
    Commented Dec 23, 2022 at 10:44
  • @Jasen It was a bit hard to see without taking down the entire fan, but indeed, it looks like the red wire from the switch is connected to both the light and fan wires in the ceiling at the same time, so it won’t work.
    – Socob
    Commented Dec 24, 2022 at 6:47
  • does the black wire in the ceiling connect to anything?
    – Jasen
    Commented Dec 24, 2022 at 7:07
  • @Jasen There’s actually three black wires up there all connected together, but none of those connect to the fan/lights.
    – Socob
    Commented Dec 24, 2022 at 7:57
  • 1
    @Jasen The fan is old, I’m just trying to install a dimmer ;-) But yeah, since there’s only one wire available for the fan & light combination, I’ll have to use another solution.
    – Socob
    Commented Dec 25, 2022 at 2:18

2 Answers 2


The black and white wires must all be connected, as in your drawing. One black is the incoming hot. That is tied to the other black that supplies the hot for your other room. The "pigtail" supplies the hot to your switch. The red is the switched hot to your fan and light. There is not a separate hot to the light and fan circuits at your fan. That switch will not work to control both. However there are fan controls that have a receiver that you put on the fan and a switch in the box that sends a radio signal to control the fan as you wish. see it here There are others that are much less expensive. Shop the net for Ceiling fan wall controls.


The black wires as connected are all hot. They supply power to the switch and also supply power to the lights in the other room. The red wire is a switched hot that supplies power to the fan and light. You would need an additional wire to the fan and light junction box for this to work the way you want it to.

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