Help with tricky 3-way switch wiring -- Fibaro Dimmer 2

Hi there,

I recently started this thread: 3-way wiring with power through light fixture - am I on the right track? that pointed me towards buying a Fibaro dimmer 2. Hopefully I’m within forum etiquette in creating a new topic, but this time I have the dimmers and have no idea how to wire them and the old title was no longer accurate.

I have 3 sets of lights, both having two switches (though I’d like to change the pendant light below into a single switch set up). I’ve wired a number of 2-way, 3-way, and 4-way dumb and GE smart switches in my house, but have never encountered wiring quite like what’s in these boxes. I’ve reproduced what I see in the graphics below, but am open to testing individual wires, etc. but just need some guidance. Any ideas?


  1. I colored the white wires in my switch boxes as yellow below
  2. It’s worth noting that the box labeled “switch box 1” in all my diagrams is the same switch box
  3. In switch box 1, there are a number of “wires to nowhere” where they are not wire nutted or stripped, just ending randomly in the box. I’ve never seen that before…


Given the loose wires in the box, which is definitely not to code, my suggestion would be that you do go ahead and map all the circuit segments Before proceeding. US code does not mandate most colors, so people can and do use any color for anything, Sometimes just depending on what spool is left in the toolbox at the end of the day. So you can’t go just by wire color.

But @Navat604 Or one of the other electrical experts in the forum can say more. @anon36505037 May also have something to add.

Thanks for the quick reply. Can you expand what you mean by “map all the circuit segments”? I don’t know how the actual fixtures are wired to the switches…the dining room would be easy since it’s just one light…but there are three pendants and 6 can lights where seeing the wiring would be tough.

that is obnoxious.

A wire tracer (fox & hound, wire toner) can put a signal on the wire and let you track it through the wall. I don’t have any particular recommendation but for example, google “buy wire tracer”:

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If you’re interested in learning all this stuff, and you live near a Home Depot, many offer a free class on wiring a light switch. It won’t cover smart switches, but you will learn how to Use the tools and what to look for In evaluating your existing wiring. Otherwise, as @anon36505037 Suggested, it might just be time to bring in a professional.

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Ohhkay. Someone did a reno on the wiring before you, and didn’t know what the hell they were doing, looks like.

It’s possible that each switch ties directly to a light, or more likely, to a junction box near one of the lights. Are they in conduit? That would explain the weird wiring color choices.

Also, the above wire tracer is primarily for low voltage phone and data cable. I wouldn’t recommend it for tracing 120V electrical wires. This Sperry tracer is quite affordable and works well for tracing live wiring. On dead wires, it won’t be much use.

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Ugh. Yeah, we had our kitchen renovated 3-4 years ago. It was a total gut, so all wiring was ran new and the electrician chose to do it this way… Somehow all the switches work as they should. I was more of a naive homeowner at the time, but it definitely “passed” whatever inspection my town gave it.

@Edward_Niedziejko There are no (exposed) junction boxes anywhere. All 3 fixtures are on the same circuit. My guess is that the ‘master’ can light is branching power to each switch (somehow) and carrying through to the other two fixtures that are then feeding power to their respective switches.

There’s a local pro who claims to specialize in home automation, but the WAF will crash if any work requires demoing a portion of the new kitchen to run/fix new wires. If that happened, I’d have to give up automating those lights… but now I’m kind of concerned there’s some kind of risk with the current ‘dumb’ setup…

Electrical code requires both the power to a device and the return path be in the same conduit or cable. There is no way the wiring is doing that with what you’ve described. Maybe pictures would be better than drawings? I’m just wondering if something’s been missed.

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so for the kitchen Can lights and dining room light. I can guess why they are like that. I do see this quite often. They were a single pole switch circuits at one point and they got converted to a 3 ways circuits or the electrician/DIY guy ran out of 14/3 romex and ended up using 14/2 instead.
Unfortuntely you have to drop the light fixtures and do more checking. I recommend using a voltmeter to check otherwise you will get confuse with a no-contact voltage checker.
Pay attention to the dark terminal screws on you 3 ways switch. They will tell you what kind of wiring config you have. put one of your meter probe on one of the 3 ways switch dark terminal and the other probe on the ground and check for voltage. The one with constant 110VAC regardless of light on or off is your line. The one with voltage only when the light ON is your load.
To check for neutral. With YOUR CIRCUIT BREAK OFF. measure resistance between a guess neutral and ground. you should get less than a couple of ohms. once you find that. redo the voltage check as above but instead of using your ground. Use the guess neutral.
use this site as a guide

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