Thermostat displays E1 and cannot control heating or cooling

Safety first: Turn off power to the HVAC system at the breaker panel before removing the thermostat from the wall to avoid shock or equipment damage.

Steps to try:

• Power cycle the thermostat: Turn off the HVAC breaker for 2–3 minutes, then turn it back on. Wait for the thermostat to reboot and see if E1 clears.
• Check for extreme temperatures: Ensure the thermostat is not installed in direct sunlight, above a heat register, or on an exterior wall that is very hot or cold. While this usually won’t cause E1, extreme conditions can trigger sensor protection.
• Inspect the wall plate connection: Gently pull the thermostat off the Amazon Smart Thermostat wall plate. Check that the pogo-pin contacts on the thermostat and the mating pads on the wall plate are clean and not bent. Reseat the thermostat firmly until it clicks.
• Factory reset: From the thermostat menu (or Alexa app), perform a factory reset and re-run setup. If E1 persists immediately after reset, the internal sensor or main PCB is likely defective.

When to replace: If E1 returns after power cycling, reseating, and reset, the internal temperature sensor on the main control board has likely failed. The thermostat assembly must be replaced; this sensor is not field-serviceable.