Thermostat displays E1 and cannot control heating; app shows sensor error or room temperature reads “--” or an impossible value.

Safety first: Turn off power to the thermostat at the circuit breaker or by switching off the boiler/HVAC control circuit. Confirm the display is off before removing the unit from the wall.

Steps to try:

• Power cycle the thermostat: Turn the breaker off for 2–3 minutes, then restore power. Check if E1 clears. If it returns immediately, the sensor is likely faulty.
• Check installation environment: Ensure the thermostat is not installed above a radiator, in direct sunlight, or near a draft. Extreme localized heat or cold can trigger sensor protection. If needed, relocate the thermostat according to Meross installation guidelines.
• Inspect the thermostat PCB (advanced): Remove the thermostat from the wall plate. Visually inspect the small NTC sensor (usually a tiny bead or epoxy component near the air vent slots) and its solder joints. Look for cracked solder or corrosion. If you see obvious damage, the sensor or main board must be replaced.
• Factory reset: With power on, perform a factory reset according to the Meross manual (usually holding the main button for several seconds until the display flashes). Reconfigure Wi‑Fi and schedules, then check if E1 persists.

When to stop: If E1 remains after reset and power cycling, the internal sensor or main PCB is defective. Do not attempt to re-solder SMD components unless you are qualified; replace the thermostat or main board module.