Google Nest thermostat code E14, E34, E84, E164, E264, E414: meaning and exact next steps
E14, E34, E84, E164, E264, E414 means A dual-fuel system (a heat pump with a backup furnace) needs an alternate heat wire, and the thermostat does not find one. This answer applies only to Google Nest Learning Thermostats (1st through 4th generation), the Nest Thermostat E and the Nest Thermostat that show a lettered help code on the display or in the Nest or Google Home app. Google prints one meaning for the aliases it groups together, and this page keeps that grouping. Codes shown by other brands of thermostat are on their own pages.
On the covered Google Nest thermostat, E14, E34, E84, E164, E264, E414 means a dual-fuel system (a heat pump with a backup furnace) needs an alternate heat wire, and the thermostat does not find one. First, confirm whether the system is a dual-fuel setup and whether a W wire for the backup heat is in the thermostat.
Confirm whether the system is a dual-fuel setup and whether a W wire for the backup heat is in the thermostat.
Correct only the documented fault domain
Reversible
Google's wiring steps: check that the alternate heat wire is in its connector and fully seated, using the setup wiring diagram. For E264 and E414 the fix is done in the Home app's wire configuration, where Google says to reset the thermostat to factory settings and add it back, entering the wires again.