Thermostat or app shows a sensor error; room temperature reading is missing, frozen, or clearly incorrect (e.g., 0°C or 50°C indoors).

Safety: Do not open the thermostat PCB unless you are qualified; this involves delicate electronics.

• Check placement: Ensure the thermostat is not placed above a radiator, in direct sunlight, near a window draft, or on an exterior wall. Relocate it to an interior wall about 1.5 m above the floor.
• Reboot thermostat: Remove one battery for 30 seconds, reinsert, and wait for the thermostat to restart. Check if the reading normalizes.
• Compare with another thermometer: Place a reliable room thermometer next to the thermostat and compare readings after 15 minutes. A small difference (±1–2°C) is normal.
• Check for condensation: If the thermostat is in a very humid area, move it to a drier location and allow it to dry out for several hours.

If the sensor error persists or readings remain extreme or absent, the internal NTC sensor or its circuitry is likely damaged; replacing the thermostat is the practical repair.