AC and Furnace coming on together

Hello! I recently installed the thermostat in my home and in a brutally cold winter, it’s kicking on my heater and AC at the same time. Here is the original setup on the furnace board. There was no C wire in the thermostat but there was on the board. I had to do the C wire adapter during set up for the Wyze thermostat and I put both the adapter C wire, and left the existing C wire that was already there on the furnace board. My fix for now was flipping the breaker on the AC and it’s at least heating the house for now.

Any ideas on how to fix this?

Welcome to the Wyze User Community Forum @gage.shirley93!

Not sure I will be able to help, but there are experts here in the forum that can! It will speed things up if you are able to also post snapshots of the C Wire Adapter connections you installed and the wall plate wire connections.

If the blue C Wire runs all the way to the thermostat but wasn’t being used, you may not be needing the Adapter at all. That wire may be hiding behind the wall plate.

Here is the original wiring at the thermostat. I labeled the wires since it’s hard to tell. I looked but I don’t think there was a c-wire hidden in the wall or behind the plate. I can check again but those wires were all bunched together, no others.
I’ll snap a pic of the current furnace board and post it as well.

Your ac unit is spliced in somewhere in series along the thermostat wire run. Right now I’d say you should just remove the Y wire from your wyze, this will stop the AC from trying to come on until you can fix the wiring. See this post for more info: Wyze Thermostat Problem - AC on with Heat - #37 by speadie


Yeah, I had read your post previously, but wanted to see if it might be the same case here. Here is a picture of the furnace board now. C wire connected was already there, and so I left it dialog with the c wire on the adapter.

And last, here is the set up behind the Wyze thermostat.

Right. the issue is that that Y wire is not a straight path from the furnace to the thermostat, it goes to the ac condenser on the way there, you need to follow the wire out of the furnace until you get to a junction point, where 2 wires should go off to the ac condenser and the other wires should go off to the thermostat.