Thermostat wiring question (HVAC has 7 wires)


I was wondering if anyone could help me with the thermostat’s wiring. I ran the compatibility check before I placed the order and everything looked fine.

I have a thermostat that is not using the C wire. In looking at the HVAC’s control board (to use with the provided adapter), I came across wiring that does not match the instructions (see the image/s below):

  • The Y terminal has two wires connected to it
  • I have wires coming from both W and W2
  • The C terminal is not free but it’s not connected to the thermostat (it’s probably going to the AC?)

Could anyone please advise on how to connect the thermostat’s adapter to the HVAC wiring? Should I use the yellow one from the Y terminal? What do I do with W2? Should I add the wire from the adapter to the existing C wire?


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ok I had something similar… only work with the wires that are the same color as the ones in your old thermostat… the other wires are there in place of power… like if yours system needs to Light a flame to kick on for fuel or case. for a wash, dryer, range, fireplace, etc… in the it is very important to follow the steps… I know that sounds adult of me to say hahaha… but has the labels due change as you move on in the setup… as you see that they change you have to adjust the wiring accordingly… as to your HVAC system and its wiring. I would swap out only the ones that are equal in color with the ones shown in your Thermostat… and as for the C wire on the adapter you will you will just add the C wire to the Circuit board from the end of the Dongle… the Wire that you on the B/C should remain in place… if you look at the Wire that is Wrapped around the bundle… that is really the C Wire but its not one that is to be used… as mine remains Wrapped… it must of been something that would have been used many Years ago with older alarm systems. sense now we have most things wireless setting off our phones and not alerting outside assistants… I do hope I Help Some… please reply if your needed clarification… hahah iv been trying to help a lot of others on different forms and my thoughts are bouncing all different ways…

forgot to add… haha later on I had to add my G wire to the C slot on the Thermostat… just Follow the photos on the setup app with the Labeling part… you’ll see what Wire ends up being the C and that should answer the question about the C wire…

Thank you for the explanation. Based on your explanation I understand that I need to:
Route the yellow wire from HVAC to the Y terminal on the dongle
Route the R, G wires from the HVAC to the R, G terminals on the dongle respectively.
Wire the dongle’s R, G, C to the HVAC’s respective control board terminals.
Add the dongle’s Y to the HVAC’s Y.
Add the dongle’s C to the HVAC’s C.

What about the W though? I have both W1 and W2 wired. Should I map just W1 to the dongle’s W terminal (and back to the HVAC)? If yes, what is the impact of not using W2?


You’re in luck, you will not need the C wire adapter.
Take the blue wire that is coiled around your thermostat wire in the furnace board and connect it to the B/C terminal with that white wire.

Then when you take your current thermostat off the wall, there is a blue wire in there that you can connect to your C terminal on your wyze.

W2 should be 2nd stage heating, so you’ll need to connect it if you want 2nd stage. As speadie said, use that unused blue wire for C so you don’t need the adapter. I suspect if you needed to use the adapter, you’d lose the 2nd stage function. The white & red wires that are connected to C & Y on the control board are going to the condenser.

@speadie, @taurensight87, @Ken.S, I much appreciate your help.

Speedie - your tip about the free wire was huge! I just wish I would have thought of it myself.

The thermostat is now up and running.

Thank you all and Happy New Year!


Sorry for the late Reply… Im so happy to have helped. and that you have gotten it working… when I read your post. i was going threw the same issue and it took me able two hrs to finally tell myself to Slow down with the setup and go threw every step.