E19 displayed and the thermostat cannot complete a firmware update; it is stuck in update mode.

Safety: No high-voltage work is required.

• Step 1 – Ensure stable power and Wi-Fi:
  • Verify the thermostat has a solid C-wire connection and is not losing power.
  • Ensure Wi-Fi is stable and has good signal strength.
• Step 2 – Retry update:
  • From the Gosund app, attempt the firmware update again.
  • Do not operate breakers or disconnect power during the update.
• Step 3 – Factory reset (if accessible):
  • If menus are still accessible, perform a factory reset and then retry the update.
• Step 4 – Recovery mode (if supported):
  • Some models support a special recovery sequence (e.g., holding specific buttons while powering on). Refer to Gosund documentation.
• Step 5 – Replace thermostat if bricked:
  • If the thermostat cannot boot normally and E19 persists, the bootloader or flash memory may be corrupted beyond field recovery.
  • Contact Gosund for a warranty replacement.