Thermostat displays E15 and reports a sensor calibration error.

Safety first: Turn off power before removing the thermostat if you will access internal components.

• Step 1 – Compare readings: Place a reliable thermometer/hygrometer near the thermostat and compare readings. Note the difference.
• Step 2 – Check calibration settings: In the thermostat menu, review any temperature or humidity offset settings. Reset offsets to 0 and see if E15 clears.
• Step 3 – Reduce electrical noise: Ensure thermostat wiring is not bundled tightly with high‑voltage lines. If it is, reroute the low‑voltage cable away from power cables.
• Step 4 – Firmware update: Update the thermostat firmware if an update is available, as calibration issues are sometimes corrected in software.
• Step 5 – Replace sensor module: If the sensor is modular and readings remain far off even after a reset, replace the indoor sensor module or the entire display assembly.