I have been trying to install a TP Link HS220 3-way switch on one of my circuits and have been running into some difficulty and I can’t figure out what exactly is going wrong. I’ll try my best to describe the situation below.

The light switches control a kitchen light and are located at the top and bottom of the stairs. The wiring in the house is older. There are typically not neutral wires run for other switches in my house. In this scenario, there is a neutral bundle in the switch box on the top of the stairs, so I was planning to install the TP-link 3 way switch there.

The first thing that I did was to confirm all of the wires in both switches. I took out both existing switches and separated all wires. I turned on the breaker and tested each one. The only live wire was located in the box on top of the stairs (the one that I want to install the switch in. I marked this as the common (line) wire. I bundled all of these together and repeated the same for the switch on the bottom of the stairs. Two wires in this switch were hot, the other one was cold. I marked the cold one as the common (load) wire for that switch. So, at this point, I was sure that I had my common and traveler wires identified correctly. The original setup without the smart switch works as it should with this configuration.

I reinstalled the switch with the old dumb switch at the bottom of the stairs. I installed the TP-Link smart switch on the top of the stairs. I connected the switch neutral wire to the neutral wire bundle in the box and connected the common and traveler wires correctly.

Here’s what happens when the breaker is turned back on walmartone. If the switch on the bottom of the stairs is on, the light works as it should, but the TP-Link smart switch has no power. If I turn the light off at the bottom of the stairs with the dumb switch, there is power to the smart switch, but the TP link switch turns on and off repeatidly after a few seconds and the light is dim and flickers. The switch never stays on long enough to even try to connect it, but the light remains dim and flickers (like it's getting some power). I made sure that I had good contacts on all of my connections (this was my first thought).

When I installed both dumb switches, the 3-way light works as it should with no issues. I am wondering if there is some funky wiring in the light itself that could allow the 3-way switch to work well with normal switches, but not with the smart switch. Is it possible that the neutral wire bundle isn’t wired properly at the light? I’m dumbfounded as to what this issue could be. Any advice would be greatly appreciated.