Hello.
Last year, I installed a 4th gen Nest, and everything was working fine. This past year, cooling was fine as well. But now when I turn the heat on, it turns the AC on instead with cool air coming from the vents. The outside AC compressor turns on as well.
Here are the things I've tried:
Switching the O/B wires in the Equipment on the Home app.
Turn off and on everything from the breakers.
Reset the Nest thermostat.
Nothing has worked so far. Interestingly, before the reset, it was detecting no power to the OB wire (which isn't even connected), but now it is not detecting power to the W wire either. I removed and reinserted it with no change.
What's also interesting is that the Home app thinks I have an electric heating system when in reality it is a gas furnace. The option to change is it greyed out.
Any ideas would be helpful.
Thanks!
*Images edited with AI to improve quality.