The thermostat is not always the villain

We replace plenty of bad thermostats. We also talk people out of replacing a good one. If one room never catches up, walk the house before you buy a control.

Closed interior doors on a small return, a sun-facing lanai, furniture blocking a return grille, or a supply that got crushed in the attic will all make a new thermostat look dumb.

If the display is blank, check the air handler switch and the float switch on the drain before you assume the wall unit died. A lot of Flagler systems shut down to keep from flooding the closet.

When we do replace a thermostat, we match what the equipment can actually do. A communicating control on a builder-grade split is a paperweight with a backlight.