A long night. A happy ending.

I recently purchased an HS210 Kit and thought tonight would be a great night to install it to help take my mind off the upcoming American Civil War and all. I expected a 30 minute task and then a few hours playing with the app and Alexa turning on and off the lights making my wife a little more than irritated.

Well, I write this summary some 5 and half hours later.

I carefully followed the instructions from the phone app and wired up the two switches. Before I buttoned them up, I figured I'd try them out. Stood at one switch: on  - off. Looks good. Stood at the other: on -off. Looks good. Now really do it: Stand at one switch on and go the other off. OK.  Turn on. Nothing. Go to the other. Turn on.  On. Turn off Off. Go to the other turn on. Nothing. Check wiring. The neutral was loose on one side. Fixed that. No change. The app sometimes turns on the light, sometimes not. Depends on the switch states. Check wiring. Loose-ish ground. Fix that. No change.

Go to the internet. A common problem apparently. Everyone says "check wiring". Way too much. They might as well have said: "Have you tried rebooting?" Still, I check wiring. It's 3 damn wires, how mistaken can I be? Really. Some other guy talks about the switches getting confused when you have multiple access points in your house. I shut them off. Still no change.

I decide it's time for a refresher on 3 way switches. On to Google. It turns out 3 way switches continue to work the same way they always have. 2 travelers and a load line. Hmm. I guess it's nice to know that somethings are predictable and stable.

Break open the voltmeter. Carefully (super carefully because I *do* hope to live long enough to eventually see a peaceful transfer of power), I measure the voltages at the travelers and common on both sides with the light on and off. I notice one switch is turning off the other switch completely. That's not right. I'd even say that's bad. Then I realize -- despite what the instructions say - there is one red traveler and one black traveler! There are NOT 2 BLACK TRAVELERS! AHA! And the RED is not the common!

Now this might be a problem related the alcoholic electrician who wired our house OR it might be a common issue. But I thought I should share it.

Since I have thrown away the old switches and not taken a picture of the original wiring (not that that would have actually been of any use) I use the voltmeter to figure out which of the two black wires is the traveler by checking the voltages (only one should be energized at a time) and which should be the load. Then I cut the power, swapped the red and black, powered up again and BOOM! WORKS!

Your summary:

There is one BLACK TRAVELER and one RED TRAVELER and the other BLACK is the COMMON. 

You might be able to distinguish your black travelers by looking at your original switch or you might have to make friends with someone who owns a voltmeter or if that's too much trouble you could wait for the FREE VOLTMETER coupon from Harbor Freight.

Anyway, I hope this helps someone.

Don't forget to check your wiring.