Thermostat shows temperature that is clearly wrong (e.g. 5°C or 35°C in a normal room).

Safety first: No electrical work is required.

• Compare with reference: Use a reliable thermometer placed near the thermostat to compare readings.
• Adjust offset: In the thermostat settings, apply a temperature offset to correct small differences (e.g. ±1–2°C).
• Improve location: Ensure the thermostat is not in direct sunlight, above a radiator, or in a drafty spot.
• Replace thermostat: If readings are wildly inaccurate and cannot be corrected with offset, the internal sensor may be defective and the thermostat should be replaced.