I'm aware that the WeMo light switch does not work as a 3-way switch, but I had purchased it before opening up the existing light switch plate and understanding the wiring I would work with.
Anyway, I removed the light switch plate and discovered what appears to be a 3-way switch. (I recently moved into this house with a whole bunch of sketchy wiring, and actually DO NOT know the location of another switch that controls that same set of exterior lights on my detached garage!) A red jumper cable is connected to the common terminal of the switch, and two black cables connect to the other terminals on the light switch. The box didn't exhibit any obvious sign of a separate (white) neutral cable.
On a lark, I decided to wire the WeMo as follows:
- Red jumper cable to the expected white, neutral terminal on the WeMo,
- Black cables to black terminals on the WeMo, and
- Capped the green/ground terminal on the WeMo.
To my surprise, the WeMo had power and booted up. However, when I pressed the WeMo button to turn on the lights, none of the garage's exterior lights turned on. I swapped the black wires and encountered the same dead end, so I restored the old switch and can turn the garage's exterior lights on/off.
I'm certainly disappointed that I didn't successfully install the WeMo, but I'm also confused. If the WeMo had power, clearly I had both hot and neutral correctly wired to the WeMo. Assuming the WeMo isn't defective, why wasn't it actually acting as a switch? What are some theories on how these lights are actually wired?