HVAC system won't turn on: The most obvious sign of a bad thermostat is that the HVAC system in your building won't turn on or respond to the thermostat. ... If you make changes at the thermostat and get no response whatsoever from your furnace, air conditioner, or heat pump, it could mean the thermostat is bad.

How do I know if my thermostat is accurate?

Checking the calibration of your thermostat is easy and should be done once a year, typically in the fall. To do so, locate your home's thermostat and tape an accurate thermometer on the wall next to it. Wait 15 minutes and check the temperature reading on both devices.

Can a thermostat temperature be wrong?

Your thermostat will read the wrong temperature if it isn't located in your home's most optimal place. If it's located near drafts or heat sources, or it's in an area that isn't centrally located, you may need to have it moved. If you can't fix your thermostat problems, contact an HVAC professional soonest possible.