You can expect a residential thermostat to last 10 to 25 years, with an average of 15 years. Here’s a few signs that it’s time to replace your thermostat:
1) Actual room temperature and thermostat don’t match.
2) Display image garbled on digital thermostat.
3) System won’t turn on or won’t turn off.
4) Thermostat screen blank or unresponsive to controls.

    Sometimes a light dusting of the interior components, especially for an analog thermostat, will bring it back to life. And corroded terminals at battery-powered thermostats can also cause an otherwise functional thermostat to stop working, along with damaged thermostat wires or wire connections. A tripped breaker in the panel is yet another reason for a dead thermostat. 

    There is one more possible solution if you have a combination gas furnace and electric air conditioner, and have recently replaced the air filter. Did you have to remove the bottom panel of your furnace/air handler to change the filter behind it? There is a safety switch along the top of the panel opening that shuts off both the system and thethermostat when the panel has been removed or is loose. Check to make sure that the panel is securely back in place so that the switch is not activated.  The switch can be a lever-type, like the one shown below, or a pop-out button.

    Eventually none of these fixes will work and it’s time to replace the thermostat. But it may be worth it to you to upgrade to a new, smart thermostat just for the energy saving features, such programmable temperature settings for time-of-day, and ability to control the system remotely from your phone.

    Also, see our other blog posts What does "AUX HEAT" and "EM HEAT" on my thermostat mean? and What is the difference between the "ON" and "AUTO" settings on my thermostat? and Why does the "AUX HEAT" (auxiliary heat) light keep coming on at my thermostat, even when it's not that cold outside?

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  To learn more about heating and air conditioning systems, see these other blog posts:

• How can I find out the SEER of my air conditioner?  

• My air conditioner won't turn on. What's wrong? 

• How can I find out the size of my air conditioner? 

• How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump? 

• Where is the air filter for my central air conditioner and furnace? I can’t find it? 

• Does an old air conditioner use more electricity as it ages? 

• How did homes stay cool in Florida before air conditioning? 

• What is wrong with an air conditioner when the air flow out of the vents is low?

• Why has the thermostat screen gone blank? 

• Why does it take so long to cool a house when an air conditioner has been off for a while? 

• Why is my air conditioner not cooling enough? 

• What are the most common problems with wall/window air conditioners?  

• Will closing doors reduce my heating and cooling costs? 

   Visit our HEATING AND AIR CONDITIONING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.