I've been installing Meross MSS550 smart 3-way switches at my house and most of them have been a breeze. However, I have an atypical setup that I have not been able to figure out. I've tried many wiring configurations, but I either get no power to the switch, power to the switch but the lights always on/off or power to the switch when the other 3-way is toggled in the correct direction.

My wiring configuration is this: 3-Way Switch (Light between switches #2

The switch's wiring diagram is this: Meross wiring diagram

This post seems to talk about my exact configuration, but I can't decipher exactly what he is doing other than connecting the line to common on the switch. I've ended up with various different problems. Lights always on, but no power to the smart switch... lights always off and smart switch has power but does nothing... etc...

EDIT Here is a picture of the switch as it was wired and working (the switch I am trying to replace). I think represents the left switch in the first diagram I posted. However, as mentioned in the comments, I am not a master electrician, so happy for someone to correct any misunderstanding I have.

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2nd 3-way switch in the circuit 2nd 3-way switch in the circuit

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    Your diagram (showing power at a switch) disagrees with your title. Could you please edit to correct one or the other? If you can't google a suitable diagram, please delete a wrong one. I'm not surprised, as there are at least five ways to wire a 3-way switch. Giving us wrong data will get you wrong answers. If the diagram were true, you'd have no trouble installing it at the left location. Dec 29, 2021 at 4:34
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    Can you post photos of the insides of the boxes involved please? Also, are you wedded to the Meross switches for some reason or another, or are you open to some other make of smartswitch instead? Dec 29, 2021 at 5:17
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    Starting with the picture and then looking all over the Meross web site, I am extremely skeptical that this device is properly certified for hardwired installation in the USA. Chinglish all over the place, no mention anywhere of certification, About Us, etc. avoid mentioning locations - finally found it, China. Chinese products made to international specs and properly certified are as safe as products made elsewhere (I'll take a Tesla made in China if you're buying) but lacking such certification I am extremely skeptical. Dec 29, 2021 at 5:22
  • @ThreePhaseEel I wouldn't say I am wedded to the Meross switches, however, I have used other brands and found these to be the most reliable so far. They have handled power outages or loss of wifi like a champ whereas other switches I have used consistently have to be reset at the slightest hiccup. I've added an image of the switch I am replacing that I hope helps.
    – ferics2
    Dec 29, 2021 at 6:14
  • Can you get us a photo looking into the back of the box depicted please? Dec 29, 2021 at 12:46

1 Answer 1


Good news: this is mostly straightforward

The good news is since the first switch box has neutral present at it, this is a fairly straightforward wiring task. First off, you need to figure out which bundle of "common" (neutral, really) wires corresponds to the incoming hot for this circuit, which'll require some tracing and matching up of wires (it's the bundle that has the white wire from the incoming hot feed you identified). Once that's done, you can incorporate the white neutral pigtail from your smart-switch of choice into the bundle, and bundle the green ground wire in with the grounds, then migrate the red and white wires from the inter-switch cable over to the traveler pigtails on the smart-switch. Finally, you can move the light over to the "load" wire from the second switch location (currently bundled in with the line wires), then connect the line-hot pigtail on the smart switch in with the identified hot bundle. Turn the breaker back on, and enjoy your new smart switch!

  • The very last step, moving the light load wire from the second switch location... etc... I didn't quite follow you there. I ended up taking the light load wire directly to the load pigtail on the smart switch and left the load bundle alone and that worked. Anyway, I think the key here was getting the neutral right and the travelers as you pointed out. Thankyou so much for your help and patience.
    – ferics2
    Dec 31, 2021 at 22:56

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