I am now attempting to wire two existing three way toggle switches to a Leviton 5643 three way combination switch for two 3-way lights on the same circuit - Pictures included.

Box 1 is what I term the “main box” because it is next to the remote for the fan. It is important to know that the fan needs continual power so the remote will work. We can turn the fan/light on and off with both three way switches located at box 1 and 2 Box 1 holds one three way switch 2 gang Box 2 holds two three way switches In Box 2 - Switch 1 (left switch) works with the fan/light In Box 2 - Switch 2 (right switch) works with the foyer light

After much work and testing I found the following.

Box 1 is providing the power to the ceiling fan/light. Box 2 is providing the power to box 1.

I ran a new wire to the 2 gang Box 2 to handle the recessed lighting. I will leave the wiring for box 1 as is for the ceiling fan/light. I will be adding a new 15a Leviton Decora 3-way combination switch to handle the power to and from the ceiling fan/light and foyer light. TOTALLY LOSING MY MIND NOW! I attempted to wire things as instructed by the combination three way switch and it tripped the breaker. I un wired everything just to see what is happening and found it odd that I was getting power from the Foyer three way wires when I have everything unconnected.

Below is Box 2 showing all of the unconnected wires except for the neutrals. This box held two three way toggles. I added a new 14/2 wire for the dimmer. Unconnected wires! The travelers to the foyer have power

Below is box 1 with 3-way toggle. Box 1 3 way toggle Switch

Below is the inside of box 1 showing two wires (one 14/3 and one 14/2). The 3 way wire goes over to box 2 and the 14/2 wire goes to the ceiling fan/light. Old Wiring

Below shows the old wiring for Box 2 Old three way toggle switches

Below shows the old wiring with the two 3 way toggles in place. Not sure why the black wires are wrapped around the two sets of travelers? Inside of secondary switch box (NOTE: Four different Romex)

Below is the wiring image I used to illustrate my situation. Obviously the wiring shown may not reflect what I have because the box 2 on the right only reflects one 3 way toggle switch. new wiring at Box 2

Two gang box from inside the closet. enter image description here

  • 3
    Is the power in the switch box, or in the ceiling box?
    – Machavity
    Jan 19, 2021 at 13:44
  • 3
    Without disconnecting any wires, pull the existing switches out of the the box and take pictures showing all the wires/cables going to all the switches. Jan 19, 2021 at 15:13
  • 1
    Can you please post photos of the insides of the boxes involved? Jan 20, 2021 at 0:56
  • 1
    Can you post photos of the inside of the other switch box for this fan/light combo please? Feb 2, 2021 at 2:02
  • 1
    No, the Dimmer is set. I had to run a separate 14/2 wire to handle that load. The issue is the 2 three way toggles being replaced by a new Model #R42-05643-0WS Leviton switch. Feb 8, 2021 at 17:31

1 Answer 1


Check your box fill

Your plan to feed the recessed lighting from and mount its dimmer at the existing two-gang where power comes in is a good one, save for one issue: box fill. You see, the NEC allocates a given amount of space for wires and devices in boxes to avoid overcrowding and its consequent issues with wire-bending and overheating. In particular, you have 18 wires in that box, consisting of 12 current carrying wires, 2 wires' worth of grounds (1 for every 4 grounds), and 4 wires' worth of devices (2 wires per gang * 2 gangs). For 14AWG wire, this yields 36in³, which is a bit more than your average two gang plastic box holds, as those cube out at 32in³. So, you'll need to check the fill capacity printed on the inside of your existing two-gang box, and replace it with an extra-large box if it comes up short.

  • So I have to remove the exiting box and replace with a three gang? Oh man that is not good. Thanks for the education but my problem with why I am not able to get the double 3-way switch to work is still pressing. Feb 9, 2021 at 10:59
  • @ChristopherLond -- you should be able to use an oversize/extra deep 2 gang box (look for one >36in3) Feb 9, 2021 at 12:40
  • 1
    @ChristopherLond -- the capped-off ends still need to be in the box, they can't be floating loose in the wall without a box to contain them Feb 11, 2021 at 0:07
  • 1
    @ChristopherLond -- yeah, those wires either need to be put back into the existing box or moved out into a new 1 gang box next to the existing box. Note that if you put a new box in, it must be accessible (i.e. not buried behind drywall!) Feb 12, 2021 at 4:57
  • 1
    @ChristopherLond -- yeah, that works as a plan Feb 12, 2021 at 12:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.