Thermostat displays E240 indicating Wi‑Fi connection failure; remote app control and cloud services are unavailable.

Safety warning: No electrical work is required for this step; do not open the thermostat if you are only troubleshooting Wi‑Fi.

• 1. Check home Wi‑Fi:
  • Verify other devices can connect to the same network and access the internet.
  • Restart the router and modem.
• 2. Check signal strength:
  • On the Lennox thermostat, view Wi‑Fi signal strength in the network menu.
  • If weak, consider relocating the router or adding a Wi‑Fi extender closer to the thermostat.
• 3. Rejoin network:
  • Forget the existing Wi‑Fi network on the thermostat.
  • Re-enter the correct SSID and password carefully.
• 4. Update firmware:
  • If possible, update the thermostat firmware via USB or local method as per Lennox instructions.
• 5. If E240 persists:
  • The internal Wi‑Fi module may be defective; replacement of the thermostat may be required.