Thermostat display shows E0 and will not connect to the home Wi‑Fi network

Safety first: Turn off power to the HVAC system at the breaker before removing the thermostat from the wall or accessing any wiring.

• Step 1 – Soft reset: From the thermostat menu, perform a network reset (Settings > Network > Reset). Reboot the thermostat by removing it from the wall plate for 30 seconds, then reattach.
• Step 2 – Check router and distance: Verify your router is powered and broadcasting 2.4 GHz (if required by your iComfort model). Move metal objects or large electronics away from the thermostat if they may be blocking signal.
• Step 3 – Verify power: With power off, pull the thermostat from the wall and inspect the R and C wires. Restore power and use a multimeter at the wall plate to confirm 24 VAC between R and C. Low voltage can prevent the Wi‑Fi module from initializing.
• Step 4 – Reconfigure Wi‑Fi: On the thermostat, go to Wi‑Fi setup and forget all networks. Re‑add your home network, ensuring the correct password and security type (WPA2) are used.
• Step 5 – Firmware update: If the thermostat can briefly connect via Ethernet bridge or mobile hotspot, check for firmware updates in the settings menu and apply any available update.
• Step 6 – Hardware check: If E0 persists and other functions work normally, the Wi‑Fi module on the main control board is likely defective. Replacement of the main control board or display assembly is typically required and is best done by a qualified technician.