WYZE Thermostat wiring help needed

I am about to wire my WYZE Thermostat and need some guidance before I screw things up.
First of all, my 30-year-old Honeywell thermostat only has 4 wires: R G Y W
My equally-old gas furnace has 5 wires: R G Y W C

I presume I need to use the C-Wire Adapter at the furnace. And other posters said you need to move the G wire in the thermostat to the C-wire terminal. Is this correct? What do I do with the C wire that’s already attached at the furnace?


You have a blue wire wrapped around the bundle coming from the thermostat. It’s very likely that you have that blue wire pushed back in your wall at the thermostat. Check that first and if you do, put the blue wire on the C at the furnace (along with the other wires already on C) and tell the Wyze app that you have a C wire during setup. If it’s not there, then install the C wire adapter. With the C wire adapter you will be instructed to relabel the G wire as C and put it at the C of the Wyze thermostat.


Thank you very much for your instructions and diagram.

However, if I attach the blue wire to the terminal at the furnace, what do I do with the other end of the blue wire at the thermostat (assuming I can find it in the wall)? Also, do I have to then run a wire to the AC Compressor (wherever that is)?

Thanks again!

If you find the blue wire in the wall, label that as C and then you’ll have G and C at the thermostat. Connect the blue wire to C and leave the other red wire there so that you have two wires connected to C. Then during the thermostat setup you’ll be asked to mark which wires you have in your current thermostat. Indicate that you have Y, W, Rc, G and C.

At your furnace, you have 2 wires already on Y (white) and a wire on C (red). You will leave those there as they likely go to your AC. So no you won’t need to run new wires. In the furnace you will have two wires on both Y and C when your done.

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I’m sorry I may have confused you… If you find the blue wire in the wall, you will have 5 wires at the thermostat:
Y - yellow
W - white
Rc- Red
G - Green
C - Blue

With those 5 wires, the setup instructions will tell you to put those into their corresponding connections on the base plate. In your furnace you will only have to add the blue wire to the C post which already has a red wire there. Leave that red wire in place.

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Haha. Yes, it can get confusing!

So you’re saying that I should attach both the G and C (blue) wires to the C terminal at the thermostat?


No, because if you have that blue wire, you don’t need the C wire adapter. You should put the blue wire to C on the base plate and the green G wire to G on the base plate. On the other hand, if you can’t find the blue wire in the wall, then you will need the C wire adapter and will need to set it up as noted in the diagram.

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Sorry to be so dense, but the base plate on the thermostat shows only Y W Rc C. There is no G.
So I will have 5 wires (including the Blue) but 4 screws to attach them to.
So where do I attach the G wire to?


Nevermind! I just saw a picture of the Wyze base plate. It does have spots for all the wires!

Well, I hooked up my thermostat, and didn’t need the C adapter, and it seems to run all right.

The only thing that puzzles me is that my furnace blower has two speeds: Low for heat (hot air is lighter) and High for A/C (cold air is denser).

Now when my heat comes on, the blower is on high for a couple of minutes, then it switches to low for the last minute or so. Normally, this wouldn’t bother me, except that the blower on high is much noisier.

I wonder if I should go back and rewire my thermostat using the C adapter? Although there was an extra blue C wire in my system, it wasn’t attached to anything. Maybe using the blue wire is causing my fan to operate on high.