Thermostat with external transformer

Mine did the same thing twice. There should be a skip option show up.

I wired it up just like the instructions pictured.


Mine did that.
I unplugged the wires from the Thermostat to be sure they weren’t touching inside the wire block.
Re-ran the check and it worked.

I just received my thermostat - should I also get a transformer? I do not have in floor heating. I am confused on this thread as to why you needed one. :slight_smile:

My battery-powered Honeywell thermostat runs on three wires to a Trane gas furnace. Do you think this same power adaptor solution that you got to work on a two-wire system would work for me? Any way to make this work with a battery (since I don’t have a power outlet near my thermostat)?

Am I right to assume I plug the new 24VAC in to C and Rc. Then I take my existing thermostat wires (currently going to W and R and those will go to Rc and W1?

Meaning Rc has two wires on it?

Can you include a link to the transformer that you are using or a pic?

Your 24VAC external transformer goes to Rc and C, your thermostat wires for your heat go to Rh and W1.
Tell the wyze that you have those 4 wires and it will switch its internal configuration to match your wiring.


Hi somebody can help me to install my thermostat? I’m really confused because I don’t have the C wire, and when open the A/C for the motherboard, I couldn’t find it, so im thinking that maybe can use a external transformer, but the old thermostat has already the cable in Rc. . Pic attached

Check behind the old thermostat in the wall for other thermostat wires. If you don’t have any, you will need to open up the air handler and use the C adapter. Show a picture of your A/C or your air handler (wherever the other ends of those wires are) and I can help you find the C wire and make a diagram for you to help you know how to hook up the C adapter.

Hello There.

Need help. I got the 24V transformer as the C wire adaptor didn’t work out well for me.

Here is a pic of my original config on the left. I then connected the transformer to C and RC as seen on the right.

Ignore that the G is dangling. I initially had it all connected. The Wyze app won’t let me proceed and flags an Extra wire in the config check. How do i hook this up properly or in the app?

thanks in advance!

You shouldn’t need a c transformer or a c adapter, as you have a blue wire that you could use for C

Thank you for spotting that. I tried it again and all I get is a clicking noise. Thermostat just keeps clicking using this config. The wyze logo doesn’t come on the monitor, but the clicking can be heard. Any other suggestions?

And for reference here is the pic of the circuit board in the AC (attic)

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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