If you think your thermostat isn’t functioning properly, there are a couple of ways you can test it. One easy way is to slowly increase the temperature setting on your thermostat. It will generally make a clicking sound, and your furnace will kick on. (You may need to have a helper stand by the furnace to see if it makes a noise.) If the furnace doesn’t respond, the thermostat is likely not sending a signal and may need to be replaced. "Some people purchase off-the-shelf temperature sensors to test if the display and air temperature match, if they’re different then that may be an indication of a larger issue," says Anand. "You can also just turn the fan on and off to see if it runs without adjusting the temperature." The easiest way to check a smart thermostat's performance is to ensure that it maintains a strong Wi-Fi connection. A poor Wi-Fi connection would lead to issues and could be a cause of poor system performance.