Honeywell Smart Thermostat Quits Working
I upgraded us to a new Smart Thermostat February 2026. The Honeywell RTH9585WF Smart Color Thermostat.
Our home is old enough that we don't have a C wire, so I used the included wire for a bridge. Furnace worked great for months. Summer rolled around and the air conditioner worked great for months.
Suddenly (in 100 degree weather no less) the thermostat quits working. When I go to use the app I have an alert that it's lost connectivity. Thermostat itself is dead in the water. Blank screen.
I had a new one in the same model so I figured I would try that. It powered on, I got it all synced with the app, we're in business again. Fast forward 8 hours, and I have another dead thermostat.
What do I need to check/photograph/look at/or test to figure out what is causing this?
