Thermostat Reading Properly

Know if Your Thermostat is Reading Properly

Do you ever feel like your thermostat isn’t quite telling the whole story? Does your home feel significantly warmer or cooler than the digital display seems to suggest? Before you call in our team of professionals at McMillin Air to replace your furnace or air conditioner, consider if the issue is with the thermostat itself. Thermostat issues tend to be easier to spot and less costly to fix than a full system overhaul. In this week’s article, we are going to show you how to test to see if your thermostat is reading properly as well as a few tips to get it back in working order.

The Paper Towel Test

Testing your thermostat is a relatively simple process. All you need is a thermometer, a sheet or two of paper towel, and some tape. Tape the paper towel on the wall next to the thermostat. Then, tape the thermometer onto the paper towel. The towel ensures that the thermometer is reading the ambient room temperature and not the walls. Leave the set-up for about fifteen minutes, then compare numbers. Disparate numbers more than a degree apart signal that your thermostat is indeed not reading properly. 

Common Culprits

Some causes of a false reading are easy to fix yourself, such as:

  • Dirty Insides. Grime and dust build-up on the inner components can easily interfere with an accurate reading. To see if this is the problem, carefully pop off the thermostat cover to reveal the interior. Use a soft, dry cloth to gently dust the surfaces. An electrical contact cleaner on a cotton swab can be used to remove corrosion on the metal contacts. 
  • Knocked Off Level. Older thermostats that use mercury to measure temperature may not function properly if slightly off-kilter. It’s not unusual for these devices to be bumped over time, which impacts how the liquid lays. If you suspect this is the case, use a level to confirm your suspicions and reattach the thermostat properly.


Other issues usually require the presence of a technician to resolve. For example:

  • End of Life. Nothing good lasts forever, and that includes your thermostat. Most devices will last around ten years. That being said, a simple replacement doesn’t always require a professional. Just remember to turn off the breaker before doing anything electrical! Upgrades, however, should be entrusted to a technician.
  • Incorrect Location. To be the most accurate, thermostats should be placed in a central location, away from direct sunlight, drafts, HVAC vents, and heat sources. If that is not the case, you’ll need to have it moved. 
  • Faulty Sensor. In some cases, the sensor has just gone caput. Try recalibrating the thermostat, but if this doesn’t work you will need to have it replaced. 


You rely on your thermostat to give you correct readings on the temperature of your home. Inaccurate numbers cause undue stress on your HVAC system and general discomfort for you and your family. If you are noticing discrepancies between your thermostat and the actual temperature of your home, and a simple cleaning isn’t doing the trick, call our team of experts today! 


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