Modern digital thermostats are more accurate and reliable than their mechanical counterparts. Still, you may encounter several thermostat problems leading to inaccurate ambient temperature readings, which can cause a negative impact on performance.
The most common thermostat problems are defective sensors, conflicting mode and settings, dust and debris buildup inside the unit, wrong wiring and installation, inappropriate location, and miscalibration. All of these can cause ineffective and inefficient temperature control.
Broken thermostats or defective sensors will need a replacement; these aren’t the kinds of problems you can troubleshoot at home. However, many common issues can be fixed by yourself. Keep reading to make sure you keep optimum climate control inside your house.
Check the Thermostat’s Mode and Programmable Settings
Contemporary thermostats have programmable settings. Some smart thermostats, like Google’s Nest Learning Thermostat, come with many customizable features. Some of these are contradictory, and a few can override others.
Take a look at all of your thermostat’s settings. Then you can use the auto or default mode to test its performance. If you’re not sure where to look, make sure you check the following:
- Ensure the fan or blower is on.
- Verify if you have selected the appropriate heating or cooling mode.
- Turn off all smart features such as ‘home,’ ‘away,’ ‘eco,’ or ‘power saver.’
Basically, let the thermostat operate on a blank slate, with the sole mission of reaching your desired temperature.
Also, be aware of the maximum heat and minimum cool levels on your thermostat’s settings. Your thermostat can’t maintain temperatures beyond or below these limits.
Clean the Thermostat for Accurate Temperature Reading
There are a few quick inspections you should perform before concluding you have an irremediable problem, like a broken thermostat or malfunctioning sensors.
To start, remove the cover or faceplate of your thermostat to check if the components inside have dust and grime buildup. Debris buildup negatively affects a thermostat’s performance.
Use a dry, soft, and nonabrasive rag to clean the thermostat components. You may use a soft brush if your thermostat is old and has coils inside. Don’t use sandpaper, gritty microfiber cloth, or any such material that can abrade or damage its internal parts..
All thermostats generate some heat due to their internal electrical and mechanical parts. This heat may influence its sensor reading by a degree or two.
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Inspect the Thermostat’s Wiring and Overall Condition
While you check for debris buildup inside the thermostat, inspect the wiring and overall condition of the unit. Any loose, frayed, or damaged wiring can cause connection problems. This, in turn, could stop your thermostat from having precise control over your heating and cooling systems.
Wiring issues usually become evident when your thermostat fails to regulate the furnace, air conditioner, fan, and HVAC units. Not all damaged wires may look frayed, so you’ll have to check for continuity.
Here’s a YouTube video on how you can test every wire on a modern thermostat:
Now you can move on to replace worn-out wiring. Make sure the wiring accurate. Many DIY installers often accidentally make mistakes when wiring their thermostats.
Keep in mind you won’t be able to fix all wiring issues yourself. If there’s any sign of physical damage, a component burnt, or extensive degradation, you may have to call for professional support. Also, if you are unsure about wiring or rewriting a smart thermostat, consult an expert, ideally a certified HVAC technician, so that wrong connections don’t damage the device.
Old thermostats using onboard mercury or air pressure and similar systems won’t function as intended if the unit isn’t perfectly leveled. Check for any misalignment and level the thermostat.
If you decide to switch from an old furnace thermostat to a smart one, you won’t use the existing two-wire connection. However, it’s not necessary to change the wiring: you can get an intermediary device to connect the smart thermostat with your furnace, air conditioner, or HVAC.
Read: HVAC Thermostat Problems
Review the Thermostat’s Installation or Location
The thermostat’s position is a common reason for temperature problems. This is also why many homeowners install more than one unit.
Ideally, a thermostat should be in a relatively central location inside your house. It shouldn’t be near the front door, windows, kitchen, or one of the bedrooms.
Keep the thermostat away from all sources of cold and heat so that the sensor doesn’t misread the ambient temperature. Also, check if there’s any mode or setting influencing the sensor’s ability to read indoors temperature.
For instance, Nest thermostats have a feature called Sunblock which detects and counters heat spikes during the day. It’s a useful feature during summer, but it can interfere with a thermostat’s routine functions in other situations, like operating a furnace or heat pump during winter.
Likewise, normal temperature control functions can lead to uneven heat distribution inside your house. If you have only one thermostat, there will be a one or two-degree difference in the temperature between the room it’s in and the farthest room from it.
The reason for this difference is that the thermostat will shut down the furnace or air conditioner after it reads the desired temperature. However, the thermometer is only measuring the room where the thermostat is located. The temperature in the farthest room from it could take longer to heat or cool.
Recalibrate Your Thermostat, Physically or Digitally
All thermostats are calibrated per factory settings. These calibrations don’t need any tinkering during installation. However, a thermostat can get miscalibrated in due course, whether it’s old or a smart variant. This is why you should occasionally test the calibration of your thermostat.
- Get a regular thermometer.
- Tape the thermometer to the wall, near the thermostat.
- Wait for 15 minutes.
- Check the thermometer’s reading against the reading on your thermostat. Any difference you find will be the offset.
- Recalibrate your thermostat’s temperature reading. The offset will indicate how much you need to rectify in your thermostat.
You can calibrate your thermostat physically or digitally, depending on the type you have and the method explained in the owner’s manual. Older thermostats have a calibration screw that you can access by removing the faceplate. Smart thermostats have a digital offset feature.
Here’s a YouTube video on how you can calibrate mechanical thermostats using bimetallic plates as sensors:
Companies have their own distinct takes on thermostat calibration. For instance, you can recalibrate Lux thermostats by accessing a feature through the menu or onboard buttons, depending on the model. Some smart thermostats like the Nest don’t have a straightforward recalibration feature, so you’ll have to restart the device and test it using the default, auto, and other modes.
Honeywell smart thermostats have an offset feature that you can toggle to increase or decrease the temperature by a few degrees. This offset will allow the thermostat to heat or cool your house to the actual temperature you’re aiming at, rather than the possibly inaccurate reading of the onboard sensor.
Calibrating digital thermostats consists simply of determining an offset of a few degrees. In other words, how much the sensor deviates from the actual temperature inside your house or room. Such offset can affect any modes, profiles, or settings on your thermostat.
Let’s suppose your thermostat is programmed to turn off after it reaches 68 F (20 C). If you program an offset of 2 degrees, the thermostat will wait until it reaches those extra degrees before turning off.
Whenever you have temperature thermostat problems, start with simple troubleshooting steps. Verify power availability, check your user settings, inspect the thermostat to assess its physical condition, ensure the connections are alright, and calibrate the unit.
If all the fixes in this guide fail to restore the unit to its former efficacy, you may be in front of a more serious problem. In such circumstances, you’ll probably need technical support from the thermostat company or some other professional.