new switchexisting switch

New to Forum...Thanks in advance.

I had my painters put in a ceiling fan / light in place of a standard light. The light and fan function fine. There are 2 switches, one on either end of room, to turn on the power to the unit. The 2 pull chains at the fan / light control the light (off/on) and fan (3 speeds).

Making improvements to this room the last couple months, I want to put this fan / light on a dimmer. Legrand makes a Fan / Dimmer control switch. I have opened the current switch, and it is connected with black, white, and red wires to a grounded box. I have not yet looked at how the carpenter / painter wired the fan.

Questions - the new switches are for either single pole or 3 way, but they have many wires coming out of the back- pairs of black, yellow, green, and red...how do i connect this? And...can i use this Legrand Fan / Dimmer switch at each switch? I have been reading that you can only use one dimmer for one switch in 3 way switch applications.

the yellow tags for the one yellow cable and one red cable with the yellow sticker says 'use this in 3-way installations only.

  • No wiring diagrams in the switch package? You're right that you can't typically dim from both switch boxes. Also, you probably purchased a dual dimmer (based on your description of the wire tails included). You won't be able to use that without wiring upgrades.
    – isherwood
    Jan 9, 2017 at 18:32
  • 3
    Did the painters replace the box in the ceiling before installing the fan? Ceiling fans require heavier-duty boxes than (most) lights do. It's imperative that the correct box is used (and supported correctly).
    – mmathis
    Jan 9, 2017 at 18:37
  • yes- they put a new bracket in that screws into the ceiling rafters as you tighten it. fan is firmly in place.
    – user64908
    Jan 9, 2017 at 18:40
  • Post some pictures of your light box and, if possible, what the fixture box wires look like. Also, here's a link to the installation PDF
    – Machavity
    Jan 9, 2017 at 20:11
  • Can you get us a picture of the inside of each switch box, with the switch unscrewed from the wall/pulled out? We need to be able to see the wiring inside the boxes... Jan 9, 2017 at 23:28

1 Answer 1


So I cut the diagram out of the PDF instructions

The reason for the red and yellow is that this is really two switches. The yellow is for your light and the red is for your fan. There's two for each, should you want to 3-way both.

The catch here is not the 3-way setup, but how you will get two hots to the box. You need one hot for the light, one for the switch and your neutral. Assuming you do, you'll take the yellow wires and attach them to the white and red that the previous 3-way used.

  • Thanks. I have looked at this diagram and it doesnt make sense to me, but regardless, just because a light is on a 3-way switch, it doesnt mean that there will be 2 hots to either of the boxes, does it? As i said, i havent line tested the lines on each existing switch yet, but one has Black White Red, and the other has 2 Blacks and one Red. Not sure if that does anything to clear this up.
    – user64908
    Jan 10, 2017 at 13:32
  • The read question is how many wires run from the switch to the fixture. You'll have to look at the junction box under the fan to find out.
    – Machavity
    Jan 10, 2017 at 13:42
  • Okay. I will do that and report back later. thank you.
    – user64908
    Jan 10, 2017 at 13:56

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