Smart switch wiring experience in an older house and 1 switch I need advice on

So after getting and setting up my know and control your home kit (which I’ll be posting a complete story on a bit later) my first venture was getting lots of smart switches in place. I’ve really found it to be challenging because of the lack of consistency of wiring around my house, which was built in 1978. With the help of my dad I was able to get around some problems which I’d like to share for comments and to give those with older homes things to think about and help prepare.

I’m using GE 45637 and 3-way 45638 switches, which have proven fine compatibility wise. I will say though, as I’ve seen other people experience the 3-way switches have a high failure rate. I had 2 that were faulty, each both cases it was the aux switch, when I took the first one back to Lowes the cashier even said he sees these come back a lot. Replacing the failed ones was hassle free through Lowes though.

Several boxes holding old switches were very shallow, I actually had to replace 2 of them to get the smart switches to fit in properly and because of shoddy construction/installation originally I had to go through a LOT of work to get some switches in.

In some cases we found wiring either much too long or too short or just messy. We did lots of cutting back to clean things up and replaced lots of couplers to make things cleaner and safer. I’d say plan on lots more time to get these installed than it would take to simply swap a switch out.

The SmartThings side of things was very quick and easy though. The only thing I wish could be done, or maybe it can is when you get lots of lights setup its hard to remember which is which in the list of things in the phone app. Sure you can give them different icons but would be nice if you could put a text label on them too, so manual turning off and on is simpler.

As previously mentioned the wiring of the 3-way switches in particular in the house was pretty inconsistent. Unknown to me there are lots of different possibly wiring configurations for 3-way switches. Here’s a good resource I found and used -

I do have 1 that we can’t figure out how to get the aux switch wired in correctly, the main is working. We’ve tried lots of different things without success including a different main and aux switch. Hoping someone out there might have an idea, as we think we just might not have the wiring we need for this one, its’ shown at the side above as Option #3


While in the Things view, shake your device. Not really intuitive, but it works…

Here’s something I did as a work around a while back:

It’s kind of a PITA, but it works. The code referenced is old, but step 2 is still the important thing - “canChangeBackground: true”

The only way I can see getting that 3way to work would be to use a CA5100 switch or something similar as the slave and then use a smart app to link them together. Then all you need for the switch is hot and neutral, no need for the traveler wire.

What are the dimensions of the gang boxes you had to use to make them fit?