E13 displayed and thermostat indicates internal clock or schedule error.

Safety first: Switch off power to the thermostat before opening the housing.

• Step 1 – Sync time via app: Connect the thermostat to Wi‑Fi and use the Atlantic app to synchronize time automatically from the internet. This often clears minor RTC errors.
• Step 2 – Manual time set: If offline, set the date and time manually in the thermostat settings and save. Check if E13 disappears.
• Step 3 – Check for firmware update: Use the app to check for firmware updates that address timekeeping issues.
• Step 4 – Inspect backup component (advanced): Some models use a small supercapacitor or coin cell for RTC backup. With power off, inspect for leakage or swelling. Replacement usually requires soldering and should be done by a qualified technician.
• Step 5 – Replace thermostat: If E13 persists and the time drifts or resets frequently despite stable power, the RTC circuit or crystal is likely defective. Replace the thermostat main module.