Nest thermostat displays E9 and may not complete setup or operate correctly

Note: E9 typically indicates an internal problem with the Nest thermostat itself rather than the HVAC system.

• Power cycle the thermostat: Remove the Nest display from the base for 1–2 minutes, then reattach it to force a reboot.
• Check for physical damage: Inspect the Nest display for cracks, signs of water ingress, or burn marks. If present, the unit is likely irreparable.
• Verify stable power: Ensure R and C are properly connected and providing a steady 24 VAC. Unstable power can sometimes trigger internal errors.
• Factory reset (last resort): If the thermostat is still responsive, go to Settings > Reset > All Settings to perform a factory reset, then reconfigure the device.

If E9 persists after these steps, the Nest thermostat display module will likely need replacement. Contact Google Nest support or your installer for warranty options.