Thermostat shows E02 and does not detect the indoor temperature correctly (reads -- or extreme values).

Safety first: Turn off power to the thermostat/HVAC at the breaker before removing the unit from the wall.

• Step 1 – Power cycle: Remove the thermostat from its wall base (if modular) or turn it off via the menu, wait 60 seconds, then restore power. Check if E02 clears.
• Step 2 – Check installation location: Ensure the thermostat is not installed above a radiator, in direct sunlight, or near drafts. Extreme localized heat or cold can cause readings that appear faulty, though they usually do not trigger E02.
• Step 3 – Inspect internal sensor: With power off, gently remove the front cover. Locate the small NTC thermistor on the user interface PCB (often a small bead or epoxy‑coated component near ventilation slots). Check for broken leads or contamination (dust, paint, condensation).
• Step 4 – Clean and dry: If there is visible moisture or dust, lightly blow out dust with dry air and allow the unit to dry completely. Do not use water or aggressive cleaners.
• Step 5 – Sensor test (advanced): Using a multimeter on resistance mode, measure across the NTC sensor leads (with the thermostat disconnected). Compare the resistance to Atlantic’s NTC curve (commonly ~10 kΩ at 25°C). An open circuit or near‑zero ohms indicates a failed sensor.
• Step 6 – Replace module: If the sensor is integrated and not separately replaceable, replace the thermostat front/user interface module or the entire thermostat assembly.