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Google Nest thermostat code H1, H2, H71, H72 and the other H codes: meaning and exact next steps

H1, H2, H71, H72 and the other H codes means A Heat Link problem on a system with a domestic hot water tank, OpenTherm, a condensing boiler, district heating or Fil pilote. H1, H71 and H151 mean the thermostat cannot connect to the Heat Link (its light is yellow); H2, H72 and H152 mean the thermostat lost power; H73 and H153 mean it cannot detect the system's OpenTherm; H155 means the Heat Link went offline when its batteries were low; H156 means OpenTherm wiring was set up without selecting OpenTherm; H157 and H158 mean the Heat Link was removed from the app or account. 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, H1, H2, H71, H72 and the other H codes means a Heat Link problem on a system with a domestic hot water tank, OpenTherm, a condensing boiler, district heating or Fil pilote. H1, H71 and H151 mean the thermostat cannot connect to the Heat Link (its light is yellow); H2, H72 and H152 mean the thermostat lost power; H73 and H153 mean it cannot detect the system's OpenTherm; H155 means the Heat Link went offline when its batteries were low; H156 means OpenTherm wiring was set up without selecting OpenTherm; H157 and H158 mean the Heat Link was removed from the app or account.

First, press the Heat Link button to turn the heating on manually while you troubleshoot, which turns hot water on too if the thermostat controls it.

Part of Google Nest thermostat error codes

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  1. What to do first

    Reversible

    Press the Heat Link button to turn the heating on manually while you troubleshoot, which turns hot water on too if the thermostat controls it.

  2. Correct only the documented fault domain

    Reversible

    Google's steps for H1, H71 and H151: hold the Heat Link's button about 20 seconds until its light turns off to restart it, move the thermostat closer or move the Heat Link at least 30 cm from the boiler and other large metal objects (with all power off at the fuse box first), remove other 2.4 GHz interference such as cordless phones, then factory reset the Heat Link. For H155, replace the batteries with new L91 Energiser lithium AA batteries and do not use alkaline. For H156, change the boiler control to OpenTherm under Settings, Equipment.

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Google Nest Help Troubleshoot Nest thermostat help codes

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What does H1, H2, H71, H72 and the other H codes mean on a Google Nest thermostat?+

A Heat Link problem on a system with a domestic hot water tank, OpenTherm, a condensing boiler, district heating or Fil pilote. H1, H71 and H151 mean the thermostat cannot connect to the Heat Link (its light is yellow); H2, H72 and H152 mean the thermostat lost power; H73 and H153 mean it cannot detect the system's OpenTherm; H155 means the Heat Link went offline when its batteries were low; H156 means OpenTherm wiring was set up without selecting OpenTherm; H157 and H158 mean the Heat Link was removed from the app or account.

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