Thermostat has only 3 wires (White, Green, Red) Wyze app says not compatible

Hello All,
My Thermostat has only 3 wires (White, Green, Red) and when I provide this to the Wyze app it says not compatible. I live in Seattle and have only a forced-air heating furnace. No cooling capability, no heat pump, pretty basic. I have attached the photo of the thermostat and the furnace control board. Can someone confirm if its still possible to use the Wyze Thermostat?

I saw in another post that we can repurpose the G wire as C by switching it on the furnace side and putting it to C on the thermostat. But in my furnace controller there is already a wire on the C that goes to the Leak Detector. Can I put 2 wires on the C terminal at the same time? Any help would be very useful. I was so excited to use Wyze thermostat :slight_smile:

At the thermostat side, I see an unused blue wire, which, provided that it goes all the way back to your furnace’s control board, you should be able to connect to the C terminal at the furnace side, meaning you would have W, G, R and C connections available. I believe that that should make it compatible.

There is some confusion in colors though, the green wire on the thermostat side seems to be just green, whereas the wire that connects to the G terminal on the furnace end seems to be green/white, although that may be a lighting issue. If there are no splices between the thermostat and the furnace, and there is an unused blue wire coming out at the furnace end (the furnace picture cuts off before we can see where the W, G, R and C wires come from), then you should be good to go.

1 Like

@vincent Thanks for the reply. Yes there is an unused blue wire that comes all the way from the furnace to the thermostat and is not connected to anything at both ends at the moment. So, Can I connect this blue wire to the “COM” terminal at the furnace end (despite there is already a black wire connected to the COM terminal in the furnace end) and the same blue wire to the C terminal at the thermostat side? And when I do this, I dont have to use the C wire adaptor provided by Wyze, Is my understanding correct?

Yep. Just tell wyze that you have a C wire after you connect the blue wire in your furnace to C. You can have lots of wires connected to C, it is just the other side of the 24V transformer.

Thanks a lot @speadie Will try it out tomorrow and let you guys know :+1:

@vincent and @speadie Thanks a bunch was able to successfully install and it and get it to working :+1: