So today I was planning on replacing the 3-way dimmers from the earlier project. This should be really simple, I obtained a GE 45857 (zigbee dimmer) and a GE 12723 (add-a-switch). Just need to pop the old ones out and replace me thinks.
Now, how could this be? I need a neutral, traveller, hot, heading towards the light, and a neutral + hot coming from the supply.
So, power back on, meter out. On the upstairs switch we have: W-B: 110VAC, W-R: 0, R-B: 0. OK, makes sense, i have line/neutral and a traveller.
But, how would this work? Somehow the neutral arrives at the light some other way, and the traveller goes naked to the other switch? But no, the other switch has 3 wires too.
Anyone have any input? I asked the great hive-mind of reddit too.