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Thermostat
Thermostat Not Working? Common Fixes
Troubleshooting a thermostat that's blank, unresponsive, or not turning the heat or AC on.
Blank screen
Replace the batteries first. If it's a wired thermostat with no batteries, the furnace may have lost power, or a safety switch on the furnace has cut power to the thermostat.
Wrong mode or schedule
Smart and programmable thermostats can be running a schedule or hold you forgot about. Check the mode (HEAT/COOL), any active hold, and the schedule.
Location matters
A thermostat in direct sun, near a lamp, or by a drafty door reads the wrong temperature and runs the system at the wrong times.
Upgrading to a smart thermostat
Some smart thermostats need a common (C) wire for power. If yours keeps rebooting or losing Wi-Fi, wiring is often the reason.