Thermostat displays E9 and backlight may be dim or unresponsive to touch

Safety first: Do not attempt to disassemble the thermostat beyond removing it from the wall sub-base; internal components are not user-serviceable.

Steps to handle E9 display fault:

• 1. Power cycle: Remove the thermostat from the sub-base for 1–2 minutes, then reinstall. Observe whether the display returns to normal.
• 2. Check mounting: Ensure the thermostat is mounted flat against the wall and not flexing. Excessive pressure or twisting can crack the display or loosen internal connectors.
• 3. Verify temperature: Confirm the thermostat is not installed on a hot wall (e.g., directly above a furnace flue or in direct sunlight). Excess heat can damage the display.
• 4. Use app (if available): If the display is partially functional, use the Goodman app to adjust settings and confirm that the thermostat still controls the system correctly.
• 5. Replace thermostat: If E9 persists and the display remains unreadable or unresponsive, the display assembly or driver circuitry has failed. Replace the thermostat with a compatible Goodman smart model.