Thermostat displays E18 and time programs do not run correctly; clock resets after power loss

Safety: No high-voltage work required.

• Step 1 – Sync time: If the thermostat is Wi‑Fi connected, enable automatic time synchronization via the internet or app.
• Step 2 – Manual set: Manually set the correct date and time and monitor if it drifts or resets.
• Step 3 – Check power stability: Ensure the thermostat supply is not being switched off by a wall switch or timer.
• Step 4 – Firmware update: Update thermostat firmware to the latest version.
• Step 5 – Replace thermostat: Persistent E18 indicates an internal RTC or backup power fault; replace the thermostat.