Thermostat displays E9 and shows incorrect or missing humidity readings.

Safety first: Turn off HVAC power at the breaker before removing the thermostat display.

• Reboot the thermostat: Remove the Wyze display from the wall plate for 30 seconds, then reattach to reboot. Restore power and check if E9 clears.
• Clean exterior vents: Use a dry, soft brush or compressed air to gently clean any dust from the small vents or openings on the thermostat where air enters for sensing. Do not use liquids.
• Check for condensation: If the thermostat is installed in a very humid area (e.g., near a bathroom), consider relocating it to a drier interior wall to prevent future sensor damage.
• Update firmware: Use the Wyze app to ensure the thermostat is on the latest firmware, then reboot again.
• Replace thermostat if unresolved: Persistent E9 after cleaning, reboot, and firmware update indicates a failed humidity sensor on the board; replace the thermostat display.