Thermostat shows F1 and cannot read room temperature (dashes or 0°C displayed)

Safety: Switch off power to the boiler and thermostat before removing the thermostat from its base.

• Visual inspection: Remove the thermostat from the wall plate. Check for visible cracks, signs of impact, or broken plastic around the sensor area (usually near the air vents).
• Check vents: Ensure the front vents are not blocked by paint, dust, or covers, which can cause overheating and sensor failure.
• Reset and test: Perform a factory reset from the settings menu and then check if the temperature reading returns.
• Measure sensor (advanced): If you have a multimeter and the NTC leads are accessible, measure resistance at room temperature (typically 10 kΩ or 12 kΩ at 25°C depending on model). An infinite reading indicates an open sensor.

If the sensor is open or the error remains, the thermostat assembly must be replaced; the internal sensor is not normally serviceable separately.