Symptoms
- Display temperature doesn't match a separate room thermometer
- Room feels hotter or colder than the reading
- Uneven comfort in different rooms
Likely causes
- CommonPoor thermostat locationDirect sunlight, drafts, nearby vents, or a hallway location can all skew the reading.
- CommonDust buildup on internal sensorDust inside the thermostat can insulate the sensor and delay accurate readings.
- PossibleCalibration driftSensors can drift slightly out of calibration over years of use.
- PossibleAveraging with a remote sensorSmart thermostats using remote sensors blend readings, which can differ from any single room.
- Less commonFailing sensorElectronic sensors occasionally fail and give consistently wrong readings.
What to do
- Compare the thermostat's reading to a separate accurate room thermometer placed nearby.
- Check the thermostat's location for direct sun, drafts from doors or windows, or a nearby heat-producing appliance.
- Remove the faceplate and gently dust the inside with a soft brush or compressed air.
- Check the settings menu for a temperature calibration or offset option and adjust it to match your reference thermometer.
- If using remote sensors, check the app to see which sensors are included in the average and adjust as needed.
- If the offset keeps drifting or is large, the thermostat may need replacement.
Tools and parts
- Separate room thermometer
- Soft brush or compressed air
When to call a pro
Call an HVAC technician if calibration doesn't fix a large, consistent error, which can mean a failing sensor.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.