Thermostat with external transformer

Is there a Blue thermostat wire at the air handler/AC? it might not be connected to anything.

Yes you are right. it’s not connected to anything. Got my hopes up when I saw it but no blue in the handler. Just this:

I tried the adaptor wyze gave and my handyman gave it his best shot and we still failed.

do you have a wider shot of the board, with more wires in view?

is this any better?

where does this blue wire go?
the one that comes out of the thermostat wire bundle

Man, you have great eyes to spot that. :slight_smile:

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It goes to HEAT on the board.

here is the zoomed in shot.


Your image shows it goes here.
Which is to say, it’s unconnected, so strip back the insulation a bit and connect it to this C terminal with the white wire that goes to the common side of your A/C compressor contactor:

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Bro you are a genius ! I finally got time to try this out and it worked on the upstairs thermostat. Will try the one downstairs tomorrow. Wyze support said the units were faulty :laughing:

Thank you again so much !

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Greetings all!

When using an external power supply does this red go to RH or RC? I see conflicting replies. The PSU i got says one end of the psu wiring shoulg go to RC and other C. Any experts out there? thanks in advance.

After you wired this up how did u set it up via the app, meaning… Did you tell the app that u have C and RC wires even those are coming from the adapter? I my case i have 4 wires R, G, Y and W and my adapter says to add the legs to RC and C so again when i go through the setup steps am i saying i have Rh, G, Y, W, RC and C? Thanks again!

If I remember correctly (it was a while ago) once I added the transformer I simply said I cad the C (constant power) wire. It may have taken 2 or 3 runs through the setup before it took.

Hilleary, your explanation and directions were PERFECT.