Thermostat C Wire to Furnace

Like everyone else who just received their new Wyze Thermostat, I’m having an issue of connecting the C wire to the furnace ( C wire to thermostat all good ). There are two blue wires if you look closely, haven’t figured out which blue wire to use as a C. Could someone chime in their 2 cents? Once a C wire is determined, I’m assuming I should screw together the C wire and red onto the C terminal. Thoughts? And thanks in advanced!!!

Here’s the terminal up close

In the 1st picture, the cable that is closest to you appears to be the cable that goes to the outside AC condenser, it’s only using the white (Y) and red ( C ) wires.

The other cable probably goes to your thermostat, just use the spare blue wire as the C wire & wire it to the C terminal on the furnace.

Meaning the cable at the back, screw the blue together with the red on the same C terminal?

Please show a picture of the thermostat wiring.
It looks like you have an extra unused blue wire in your thermostat bundle. If you connect it to C on the furnace and C on your thermostat, then you do not need to use the adapter.
Note that C has a red wire from your outdoor unit going to it right now.
Where does the red wire from the thermostat bundle go?

Yes, just like the Y terminal has 2 wires, 1 goes to the outside AC condenser and the other goes to the thermostat. The C terminal will be wired the same way with 2 wires.

I don’t have any pic but it’s a straight forward connection. Red goes to R, Green goes to G and so forth. And yes, there’s an unused Blue wire, so I connected it to the C on the thermostat but no power. Then I noticed the other end of the Blue isn’t connected to the furnace

Thanks. I’ll try that method tomorrow and keep you updated

The issue is that from the pictures you have provided I cant tell where that red thermostat wire actually goes. it doesn’t go to R on the control board, it goes out of the frame to the right. Is it going directly to the transformer? The black wire that is connected to the R terminal also goes out of the bottom of the picture as well.

Thanks Ken!!! Totally fixed the issue. You’re a life saver. Saved me $$$ from calling a hvac technician

Cool, glad to help

Hi Ken,

We only have a red and a white wire on a standard Honeywell thermostat. Our Wyze app is saying it is incompatible? Seems like a pretty straight forward system and had no trouble with the nest. Any advice?

Thanks! Most appreciated

My understanding is that a 2 wire system is indeed incompatible. Nest uses a battery, Wyze needs to be powered by the 24v system/transformer. Just for kicks, post a picture of your wiring at the thermostat & furnace

Thanks Ken

do u have multiple thermostats? Also, is this a heat only system? your pic at the furnace shows 4 zones. based on what I’m seeing, I’m not sure the Wyze thermostat would work for you if you have multiple thermostats. Even if there was only 1 thermostat, you would need 1 more wire to use the wyze C wire adapter. The only other way it would work is if you used a separate transformer/adapter, like the one below, then you would use only the W wire on your existing wiring for heat.

4 zones and three thermostat. ( One zone dedicated to hot water tank.

One zone I replaced the honeywell thermostat with the nest a while back simple install. In the past couple of years I have about all that Wyze has to offer in product’s. I figured I would now put the thermostats in. I now understand that they are not compatible with a two wire system. Thanks Ken for all your help. Len

On your zone board, there is a green connector on the left side. You can get common from here, although you’d need to run a wire from there to wherever the thermostat is.