Thermostat displays E5 and the fan will not respond to manual or automatic commands.

Safety first: Turn off power to the furnace/air handler at the breaker.

• Check G at thermostat: Remove the Wyze display and verify the G (often green) wire is fully seated in the G terminal. Re-strip and reinsert if necessary.
• Inspect G at furnace board: At the control board, confirm the same colored wire is attached to the G terminal. Tighten the screw and ensure no stray strands are touching other terminals.
• Verify adapter wiring: If using a Wyze C-Wire Adapter, confirm the G wire from the thermostat is in the correct adapter port and the adapter’s G lead is on the G terminal at the control board.
• Continuity test: With power off and G disconnected at both ends, use a multimeter to check continuity of the G conductor. Replace the thermostat cable if the conductor is open.
• Restore power and test fan: Reconnect all wires, restore power, and set the Wyze thermostat fan mode to On. The E5 code should clear and the blower fan should run continuously.