Wyze Thermostat installation issues

I’m trying to sort out my Thermostat wiring issues. My furnace/air conditioning unit is up in my attic and hard to get to. But I did and I found that the control board only has three wires that come off of it to the thermostat. Wires are: Red Green and white. Power appears to come from a transformer that is mounted on a ceiling joist. I don’t know why, but they connected the ps to the yellow wire that goes down to the T-stat. So, at the t-stat I have yellow going to the C terminal, Red wire to the Rc terminal, White to W1 and Green to G terminal. The Small blue wire is not connected to anything.

I have heat working but the A/C does not come on.

I live in South Houston Texas, so A/C is a must.

![image|375x500] (upload://szGHiPdMLBz81iN4hBuGI0jT2hA.jpeg)

I can provide more details if needed.

Thanks in advance
Rick R

Yeah, somethings not right. The yellow Y at your thermostat shouldn’t be going to C but to Y on the control board. Y is for AC which might explain why AC is not working. Did you install the C wire adapter? Can you post more pictures of the wired wyze thermostat and if possible the control board too?

1 Like

Here are the wires that live inside my unit. Coming off of the circuit board are the Red, white, and green.

The yellow wire going down to my thermostat, is connected to one of the leads from the transformer.

I have another furnace on the other side of the attic and there is a yellow wire coming from it to the same transformer 24vdc also.

I will get back up there this weekend and take more pictures of the adapter as well. Thanks for responding.

Here’s how you should have hooked up your C wire adapter.
I’m betting you hooked up the A/C compressor wires to the wrong side of the adapter or interrupted the C wiring to the compressor when you installed the adapter.


Thank-You very much. Your diagram is exactly what I needed to get this thing working.

I can’t say thanks enough. I have one more to install, and now with your helping me it won’t take as long to install it.

Thanks again,
Rick R.

I thought it was working. The ac is not coming on. I’ll have to get back up there and see what I did wrong. It’s not coming on with either of my two units. Heat works fine but the ac is not.

I’ll take and post pictures of my connections.


Take a picture of the C adapter wiring, and post it here,

image image

Hi well I have more info.
There are two pig tails that enter the unit. The first pigtail has red, green, yellow and white. This is what you see wired into the adapter.

The second pigtail has, red yellow and white.

Following your diagram I connected the yellow wire to the C wire from the adapter, the red I connected to the to the y wire coming from the adapter.

In this configuration my t-stat has no power and the unit will not turn on at all.

If I connect the red wire to the C wire on the adapter wire and the yellow wire to the y-wire coming from the adapter, my unit starts and I have heat, but no a/c.

From the second pigtail that has the red and yellow wire, there is a white wire connected to a blue wire coming from the circut board cluster of wires. I have no idea what that is used for.

Plus I’m color blind, and have to get my wife to tell me which wire is which.

Thanks for your assistance with this, I’m not afraid to do the work myself, but I’m at a loss on how to make this thing work.

The yellow wire from the A/C compressor shouldn’t be connected to C
The C wire that is currently attached to the yellow wire needs to go into this wire nut, with the white A/C wire and the purple furnace wire.
The yellow wire from this bundle of wires ( that go to your a/c compressor) wasn’t attached to anything originally, was it?

I don’t suppose that that blue wire that I see wrapped around the other wires is in the wall behind your thermostat?

Thank you again for helping me.

If you look at the picture at the beginning of this post you can see that the small yellow wire and a small red wire are twisted together in the same wire nut.

Just so I’m clear on this, the c wire from the adapter ribbon cable should go to the purple wire and white small wire nut.

That would leave the ribbon Y wire not attached to anything?

I will try your recommendation this morning and report back when done.


You have 2 yellow wires. One goes to your thermostat, that one used to be attached to the red wire, and is now attached to the wyze adapter’s screw terminal that is labeled Y. The other one shouldn’t have been attached to anything.

I’m not asking you to do anything with the Y ribbon wire, leave it wire nutted to the red wire that goes to the A/C unit.
Your C wire will have 3 wires in its wire nut - large purple from furnace, small white to A/C, and the C ribbon cable from your wyze adapter. This is normal.

1 Like

Connected Red from outside unit to yellow ribbon cable wire. Connected C grey wire from ribbon to the purple and white wires on my downstairs unit.

BINGO! I now have heat and a/c. Damn you are good Mr Speadie!

Starting on upstairs unit now.

I can’t say thank you enough. Beers are on me!



Upstairs unit is now working also.

Again, thank-you Speadie!!!