Wyze thermostat - 3 wires - incompatible?

Hi - I had my hopes up that my thermostat preorder would work fine with my system but the app says it’s incompatible. After seeing some suggestions here for others with three wires (different colors than mine) I’m hoping there’s a workaround.

I have Red, Yellow, and Green wires as shown in this lousy picture I took a few days ago:

My current thermostat is a battery-powered Honeywell. I saw some people were advised to use a 24v transformer but I don’t have a power outlet near my thermostat.

Any advice? Is the magic man, @speadie out there?

Use the C wire adapter. W isn’t needed as far as I can tell. you might need to tell your wyze you have a W wire in order to get it to tell you to use the C wire adapter though. Just to verify, your system is cooling only?

If you want me to talk you through hooking up the C wire adapter, I’d need a picture of your air handler or AC unit, wherever the transformer that is feeding that red wire comes from.

Thanks for the quick reply, Speadie. I should have been more clear, sorry. I live in Seattle and have only a forced-air heating furnace. No cooling capability, no heat pump, pretty basic.

Ah. Do you need independent control of the fan? if not, you can use the Green wire as C instead, by removing it from the G terminal on your furnace and putting it on the C terminal.

If the furnace fan will not run without the G wire connected, you can always put a jumper on the furnace between G and W1, but most gas furnaces will control their own fans without you needing to do this.

I’ve tried turning on the fan manually in the summer to circulate air, but it doesn’t make any real difference, so I’d be fine not having independent control over it.

So if I understand you correctly, I basically treat G as C, so I tell the App in setup that I have Y, R, and C? Do I need to move G on the furnace side?

No, if you have heat, tell the app that the yellow wire is W. Tell it you have Rc, C, and W. You will need to move the G wire in the furnace to the common terminal as well, otherwise your fan would run 24/7.

W= heat
Y= compressor (A/C)
G= fan
R= hot

Thanks for bearing with me, I’m an expert at tech but a beginner at wiring!

Thermostat side move:
R → Rc
Y → W
G → C

Furnace side move:
G → C

I’ll post an update end of day when I can try this out.


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YES! It worked. I’m so psyched. @speadie, Wyze should be paying you :medal_sports::medal_sports::medal_sports:


I’m going to start on this after I contact the seller of “Mr. Cool” Universal heat pumps. I get an incompatible notice on the app. ,but any suggestions would be appreciated.

This is the current wiring which is working with a simple Honeywell thermostat.

Your wires are, from left to right:
Aux, G. O/B, C. Y, Rc
This is compatible with wyze.

Thanks for that speedie. I just got home so I’ll try it again. Pull the jumper, yes?

The wyze does not require a jumper, just put the red wire into Rc

I am thoroughly confused about how to wire the current heat-only system (see photos) to the Wyze Thermostat. On the furnace side, there are W, R and G wires connected Any assistance would be greatly appreciated!

I need a picture of the furnace side.

Are the blue and yellow thermostat wires that are available at the thermostat also available at the furnace?

If so, with the power to the furnace off, strip the blue wire insulation back about half an inch and attach it to the C terminal on the furnace board.
On the thermostat end, strip the blue and green wire insulation back to expose the wire and put the wires into the following terminals:
Red: Rc
Green: G
White: W1
Blue: C
Tell the wyze app that your “old thermostat” has the following wires: R,G,W,C

Yes, those wires are available at the furnace. I will follow your directions tomorrow and let you know how it goes. Thank you so much for the assistance!

One last question before I begin: Would you recommend using the C Adapter at the furnace, or is that unnecessary and just go with what is at the furnace?

You don’t need the C adapter because you have a spare wire for C.

Thanks for all your help! It works perfectly and your assistance was invaluable, and much appreciated!

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