Think Your Thermostat's Lying To You? Here's What You Can Do About It

16 June 2016
 Categories: , Articles


HVAC thermostats are usually accurate when it comes to measuring room temperatures, but there's always the possibility that your thermostat's readings might not match up with the actual room temperature. If your home feels hotter or colder than your thermostat's letting on, then there may be a fault within the thermostat. The following explains why thermostat temperature errors happen, what causes them and how you can fix these issues on your own.

What Causes Bad Thermostat Temperature Readings

There are plenty of factors that could cause your thermostat to read incorrect temperatures. For starters, having your thermostat in the wrong location can give you the wrong temperature readings, since external sources of heat and cold can easily alter temperatures sensed by the thermostat. Dust and dirt can block the air inlet openings around the thermostat, making it difficult to sense temperature changes properly. On older thermostats, knocking the unit out of alignment could also prevent it from reading temperatures correctly.

Another culprit to look out for is excess humidity. In an overly humid environment, the air can feel warmer than it actually is due to the lack of an evaporative effect. This can cause your skin to feel sweaty, sticky and make you feel uncomfortable overall.

Putting Your Thermostat to the Test

When it comes to checking your thermostat's temperature readings, it's always a good idea to get a second opinion. To do this, all you'll need is a small digital thermometer, a piece of paper towel and some tape:

  • Place the paper towel on the wall next to the thermostat and use the tape to hold it in place.
  • Tape the digital thermostat directly to the paper towel. This will help isolate the thermometer from the wall so it can read the air temperature instead of the wall temperature.
  • Leave the thermometer in place for approximately 15 minutes so that the thermostat can give a stable reading.

Compare the results seen on the thermometer to the readout on the thermostat. If they both match up, you're likely dealing with a humidity issue that can be taken care of with the help of a dehumidifier. If not, you'll need to see the below options for correcting the issue.

Fixing the Issue

There are several ways you can fix your thermostat's incorrect temperature readings:

  • Check the thermostat's location. Ideally, it should be installed on an interior wall near the center of your home, well away from any sources of heat or cold. If the thermostat is in an area that's exposed to direct sunlight or draft, you'll need to relocate it to a more appropriate area.
  • Make sure the thermostat is level. An accidental bump or nudge on an older thermometer with mercury bulbs could easily leave it off-kilter, resulting in strange thermostat readings. Use a bubble level to carefully readjust the thermostat.
  • Clean the inside of the thermostat. Dirt, dust and grime can accumulate inside the unit over time and cause errors. Carefully open the thermostat and use a soft brush to remove any debris found within.
  • Clean the thermostat's contacts. The electrical contacts can get dirty and/or corroded with age and use. Use electronic contact cleaner and a soft cloth to clean up the contacts. If the contacts are corroded, you may need to remove the corrosion with a small piece of fine sandpaper.
  • Use a dehumidifier to lower your home's relative humidity. Like your A/C system, a dehumidifier removes excess moisture, but in larger quantities. For the best comfort possible, your home's relative humidity should be no more than 50 percent during the summer and 40 percent during the winter.

If you're still getting faulty temperature readings from your thermostat, then you might have no other choice than to replace it with a newer unit. According to CostHelper, the average programmable thermostat costs $25 to $250, depending on the model and features you choose. A seasoned HVAC contractor may charge $75 to $150 to install it for you. For more information, contact a company like Elite Heating, Cooling and Plumbing.