Troubleshooting
Thermostat Not Working
Quick answer
Replace the batteries first. Then check the breaker for the HVAC system. If both are fine and the screen is blank, the thermostat itself or the wiring is the issue.
Common causes
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Dead batteries
easyMost common. Most thermostats have AA or AAA batteries you can replace yourself.
-
Tripped HVAC breaker
easyIf the thermostat is hardwired (smart thermostats often are), no power to the unit = blank screen.
-
Loose wire on terminal block
moderateA wire backed out of the screw terminal. Re-tighten.
-
Failed transformer
moderateThe 24V transformer in the furnace fried — no control voltage. Tech replacement.
-
Dead thermostat
moderateIt eventually happens. Smart thermostats around the 7–10 year mark.
DIY first
- 1 Replace batteries.
- 2 Pop the thermostat off the wall — check the wires are seated firmly in the terminal block.
- 3 Check breaker.
- 4 Look at the furnace status light — if the furnace has power but is waiting for a signal, the thermostat is dead.
Call us if:
- All above failed
- Breaker re-trips
- You smell anything burning
Other symptoms in this category
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