Installing the Wyze Thermostat with no circuit board

Darn! I got the dreaded nest of wires when you search for a nice and tidy circuit board :see_no_evil: !

What I have found is that I do have an unconnected red wire at my thermostat and at the furnace. Could it be that I do have a C wire after all? I have no idea where to connect the Red to on the furnace end but I assume it would go to my Rc on the thermostat end Would that make the blue my C ?

Anyone know if there is some other reason to use the No C wire adapter instead of adding this red to an existing connection? As it is, I’m nervous that these connections are sketchy since they are not in a terminal.

Here is the thermostat end… See that little red hiding!? Could that go into the Rc?

I wonder if the red wire has a fault and that’s why they used light blue instead. Really, it doesn’t matter what color wire is used, it’s just making a connection from the thermostat to the system.

I have a feeling that dark blue wire on the furnace side is the C. Maybe @speadie will know. If it is, you can try using the unused red wire for C, unless you want to make the red wire Rc and the light blue C, which is more standard.

One thing you could do as a test with your old thermostat is replaced the light blue wire on both ends with the red wire and make sure it’s still working. If it doesn’t work, switch it back to the light blue.

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They might have used the blue wire for hot to show that there is a float switch lockout on the hot side.
You should try connecting the red wire on the furnace end to the wire-nut with the blue and white wires in it and the C connector on the wyze side.

if that works, it is worth swapping the R and C wires on both ends of the thermostat run, just to make it easier on the next person who takes the thermostat off the wall, so that the wires are using the standard color coding.

With it swapped the diagram looks like this:


We have power!!! :muscle: :zap: I ONLY added the unconnected R to the White/Blue bundle at the furnace, and then on the thermostat side I used your step 1 diagram. Unfortunately, still missing something because it is failing the function tests. The app had me pull my G from the thermostat, and after running the tests the fan isn’t kicking on inside, only outside. (Which I guess makes sense since G is for the fan right?) Not sure how to get around the app test saying I have an extra wire.

This zoom in picture was SUPER helpful to know exactly which bundle to approach… thank you!

Going to test your faulty wire theories tomorrow with the old thermostat. Had to switch it back to the old one anyways to have it run overnight (again :woman_facepalming: ) but would like to rewire it with the more standard light blue C and red RC like @speadie suggested if I can! Once I can get it running that is!

Ignore the thing that tells you to remove the G wire, if instead you press keep trying, eventually it will let you skip the error.
Wyze really needs to remove this wire detection feature, if it makes poeple remove wires that their system needs.

ahhhhhh!!! That then I will try first thing tomorrow because it was the ONLY thing that seemed logically off ( … I mean other than blue going to Rc and no “common” and having random unconnected red cables at both ends just asking for a smart thermostat… and the mess of wires at my furnace I was left to sort through haha)

I wonder why they app flags the G wire like that? Seems like a logical thing to have a G connected for people who want to run the fan only with no need to activate the hot or cold W or Y… (but I’m no HVAC expert I just like to learn how things work.)

If your furnace has a protection circuit on the fan, the wyze will see it as not actually being connected because it cant get a signal from it through the protection circuit. It’s an error, but the wyze isn’t smart enough to know that.

Check out the note I got on the first try of the day!!!

Not sure what changed from yesterday, I did do an update first to the app just to be sure there were no issues on that end. Hope the feature you mentioned @speadie has been made “smarter” overnight and that this might not be a problem for people in the future - you are TOTALLY right that the app was convincing me that the G would not be needed even though logic said otherwise.

Thank you @speadie and @Ken.S for helping me get this up and running! I had tried tackling it on my own researching HVAC systems and smart thermostats for the last week and was feeling pretty defeated - yall saved me from yet another day of trying to figure it out alone… yay WYZE community! We did it!

PS: this was WAY more than a 30 min install for me! In addition to the compatibility test, it might be helpful for WYZE to have people check to see if they have a terminal at the furnace as well at this step so that people can plan appropriately (even if that means hiring an expert to do the install). I 100% would have still purchased this thermostat… we are a WYZE family with our whole house set up on it from cameras to (soon!) the vacuum and have been holding out for this smart thermostat to happen… but it would have been good to know that it may not be as simple if you have no circuit board on the furnace end.