Thermostat shows E18 and reports humidity sensor error (on models with humidity)

Safety first: Do not spray cleaners directly onto the thermostat.

• Clean the vents: Gently vacuum around the thermostat’s ventilation slots to remove dust. Do not insert tools into the vents.
• Stabilise environment: Avoid placing the thermostat in bathrooms or above kettles where steam is frequent.
• Reboot and update: Power-cycle the thermostat and check for firmware updates via the Wiser app.
• Compare with another hygrometer: If readings are clearly wrong and E18 persists, the sensor is likely defective.
• Resolution: Replace the thermostat; the humidity sensor is integrated and not serviceable.