Is my furnace thermostat bad?
You first want to ensure that there’s no power going to your thermostat, so shut off any breakers or other power sources for about twenty seconds. If this doesn’t work and the pilot light stays lit on your HVAC system, check if anything obstructs the burner on your furnace, preventing it from heating up properly.
A thermostat is simply a digital or mechanical device that controls the temperature in your home. It does not actually “turn on” your furnace, but it does turn it off and on as needed to maintain the temperature you’ve set on the thermostat. You may notice this because it’s getting colder outside, and your home’s heated air may be blowing out warmer air from another room heated by your furnace.
Heating and cooling systems can be tricky to diagnose, especially as they age. Keep in mind that there are a variety of other issues that can cause heating problems. It might have nothing to do with the thermostat.
The first thing you should do is see if the thermostat is bad by changing the battery. Thermostats rely on batteries for power, so it’s possible that a low or dead battery could be causing problems with your heating system. If your furnace still isn’t working after replacing the battery, then proceed to check all the connections from the thermostat to your heating system and check for any loose wires, which may have been knocked loose when you replaced or moved the thermostat.