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Thermostat Not Working

When you walk into your home any time of year, you expect it to be comfortable, right? When it’s noticeably hot or cold, where is the first place you check for a problem? Typically, it’s the thermostat to see at what temperature it is set. Upon further investigation you may come to find that your AC thermostat is not working! You may see a blank screen, flashing numbers or be unable to switch it from heat to cool mode and vice versa. The next question is “why is my thermostat not working?” Then what do you do next?

nest thermostat

We will go over some easy DIY things you can check to see if your thermostat is not working or if something else HVAC-related might actually be going on that may require repair.

Just remember B-B-S: Batteries, Breaker, Switch

  1. Batteries

If your thermostat is not working the first (and easiest) thing to check is the batteries. If your display is completely dark, then this is a likely culprit. Just pop off the thermostat and check to see if the batteries are old or corroded. Swap them out for new ones and see if your thermostat display begins working again or other issues resolve. If they do not, then move on to our next “B.”

  1. Breaker

If swapping the thermostat batteries doesn’t help, then check the breaker box to see if the breaker controlling the thermostat may be switched off. If it is, turn it back to “on” and see if this remedies the problem. If it still trips repeatedly, then leave the breaker in “off” mode and call an HVAC company to further investigate.

  1. Switch

If the batteries don’t fix the problem and the breaker has not been tripped, then the last place you can check for an issue when your thermostat isn’t working is the furnace switch on the side of your furnace (it may also be mounted on a nearby wall). This switch is used to disconnect the power to the furnace. If it is off, then that is most likely the reason your thermostat seems to not be keeping temperature correctly and not an issue with the thermostat itself.

It may be tempting to just ask for a thermostat replacement when it seems like nothing will fix your thermostat to heat and cool properly. However, 90% of the time when it seems like your AC thermostat isn’t working, it is actually an underlying HVAC issue with your furnace or air conditioner rather than needing a new thermostat replacement. furnace switch with arrow

Other Issues That Can Make You Think Your Thermostat Isn’t Working


If your thermostat is reading a temperature that you know is not correct based on how you’re feeling in the home and the frequency your heating and air is running, the location of the thermostat could be the issue. If it’s in a spot near a door, getting direct sunlight from a window or close to a supply register, then it may be reading too warm or cool based on the immediate surrounding environment rather than the actual temperature in the room. The only way to fix this issue would be to relocate the thermostat.

Safety Features

Some digital thermostats are built in with a 5-minute delay. If you lose power or switch modes from heating to cooling or vice versa, there will be a 5-minute delay before the thermostat sends the signal to the HVAC system, so it does not cause a power surge. So, if you’re switching modes, wait a few minutes to see if the heat or air kicks on before assuming that the thermostat is failing.

If you’re near Cincinnati, OH and have a thermostat that isn’t working, give Quality Comfort Home Services a call at 513-620-HVAC or book service online anytime!