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Google Nest thermostat code N1, N21, N71, N401 and the other low-power N codes: meaning and exact next steps

N1, N21, N71, N401 and the other low-power N codes means One wire is receiving power, but less than expected. Google names the wire for each code: N1, N21, N71 and N401 mean the Rc power wire is not connected to equipment; N2, N22, N72 and N402 mean the same for Rh; N3, N23, N73, N153 and N403 are W1; N4, N24, N74, N154 and N404 are Y1; N5, N25, N75 and N405 are W2/AUX; N6, N26, N76, N156 and N406 are G; N7, N27, N77 and N407 are O/B; N28, N78 and N408 are Y2; N29, N79, N159 and N409 are the star wire; N414 is no power to AQ+ on a one-wire accessory and N415 is an AQ- wire without an AQ+ wire. 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, N1, N21, N71, N401 and the other low-power N codes means one wire is receiving power, but less than expected. Google names the wire for each code: N1, N21, N71 and N401 mean the Rc power wire is not connected to equipment; N2, N22, N72 and N402 mean the same for Rh; N3, N23, N73, N153 and N403 are W1; N4, N24, N74, N154 and N404 are Y1; N5, N25, N75 and N405 are W2/AUX;

N6, N26, N76, N156 and N406 are G; N7, N27, N77 and N407 are O/B; N28, N78 and N408 are Y2; N29, N79, N159 and N409 are the star wire; N414 is no power to AQ+ on a one-wire accessory and N415 is an AQ- wire without an AQ+ wire. First, turn off the system power, pull the display and look at whether the connector named in the code has its button all the way down.

Part of Google Nest thermostat error codes

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  1. What to do first

    Reversible

    Turn off the system power, pull the display and look at whether the connector named in the code has its button all the way down.

  2. Correct only the documented fault domain

    Reversible

    Google's "Low power to thermostat" steps: check that every connector with a wire is down, re-insert the wire as far as it will go, strip about 1/3 to 1/2 inch of straight copper if needed, press the display back on and restore power. If the code returns but the system runs normally, Google says you can dismiss the message and keep using the thermostat, and that it should not pop up again after you dismiss it, though you may want a professional to check the system.

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Google Nest Help Troubleshoot Nest thermostat help codes

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Common questions about “Google Nest thermostat code N1, N21, N71, N401 and the other low-power N codes”

What does N1, N21, N71, N401 and the other low-power N codes mean on a Google Nest thermostat?+

One wire is receiving power, but less than expected. Google names the wire for each code: N1, N21, N71 and N401 mean the Rc power wire is not connected to equipment; N2, N22, N72 and N402 mean the same for Rh; N3, N23, N73, N153 and N403 are W1; N4, N24, N74, N154 and N404 are Y1; N5, N25, N75 and N405 are W2/AUX; N6, N26, N76, N156 and N406 are G; N7, N27, N77 and N407 are O/B; N28, N78 and N408 are Y2; N29, N79, N159 and N409 are the star wire; N414 is no power to AQ+ on a one-wire accessory and N415 is an AQ- wire without an AQ+ wire.

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