How to Fix / Troubleshooting

Safety first: No high-voltage work is needed for calibration.

Steps to troubleshoot:

Place a reliable thermometer near the thermostat and compare readings.
In the thermostat settings, adjust the temperature offset until the displayed value matches the reference thermometer.
Seal large holes in the wall behind the thermostat to prevent drafts from affecting the sensor.
Relocate the thermostat to an interior wall away from direct sunlight, exterior walls, or heat sources.
If large offsets (>3–4°C) are required to match reality, the internal sensor may be defective; replace the thermostat.

Thermostat shows room temperature much higher or lower than actual by several degrees

Possible Causes