Thermostat shows temperature that is clearly inaccurate compared to other thermometers

Safety first: No need to power down HVAC; work only at the thermostat.

Steps to troubleshoot:

• 1. Compare readings: Place a reliable digital thermometer near the thermostat and compare readings after 15 minutes.
• 2. Check for drafts: Remove the thermostat and feel for air movement from the wall cavity. Seal large openings with non-flammable insulation or foam.
• 3. Avoid heat sources: Ensure the thermostat is not above electronics, lamps, or in direct sunlight.
• 4. Adjust offset: Use the thermostat's temperature offset/calibration feature to align the displayed temperature with the reference thermometer.
• 5. Recheck after adjustment: Allow time for readings to stabilize and verify accuracy.

When to call a professional: If the thermostat cannot be calibrated within a few degrees, the internal sensor may be defective and the thermostat should be replaced.