Thermostat displays E13 and indicates sensor calibration error

Safety first: Turn off power to the HVAC system if you will remove the thermostat from the wall.

Steps to troubleshoot:

• 1. Compare with reference thermometer: Place a reliable digital thermometer near the thermostat and compare readings after 15–20 minutes. Note the difference.
• 2. Adjust calibration: In the thermostat settings, locate the temperature offset or calibration option. Adjust within the allowed range (often ±5°F) to match the reference thermometer.
• 3. Check for drafts or heat sources: Ensure the thermostat is not affected by drafts from doors, windows, or supply vents, which can skew readings.
• 4. Clean sensor vents: Use dry compressed air to gently clear dust from the thermostat vents.
• 5. Factory reset: If E13 persists, perform a factory reset and recheck calibration.
• 6. Replace if out of range: If the thermostat reading is still far off even at maximum offset, the sensor has likely drifted beyond usable range and the thermostat should be replaced.

When to call a professional: If the thermostat is part of a multi-zone or building automation system, have a technician verify calibration across zones.