Thermostat displays E8 and humidity readings are missing or inaccurate

Safety: Turn off power to the HVAC system before removing the thermostat.

• Step 1 – Visual inspection: Remove the thermostat from the wall and inspect for signs of moisture, corrosion, or dust buildup on the sensor area (usually vent slots).
• Step 2 – Gentle cleaning: Use dry compressed air to gently blow dust from the thermostat vents. Do not use liquids or cleaners.
• Step 3 – Stabilize environment: Ensure the thermostat is not installed in a high-humidity location such as directly above a humidifier outlet or in a bathroom.
• Step 4 – Firmware update and reboot: Check for firmware updates and reboot the thermostat from the settings menu.
• Step 5 – Compare humidity: Use a separate hygrometer to compare readings. If the thermostat remains far off and E8 persists, the internal humidity sensor has likely failed and the thermostat should be replaced.