Nest thermostat: N72 and other N codes: low power to the thermostat
One of the wires in your thermostat is receiving power, but less power than expected.
Applies to: Nest Learning Thermostat, Nest Thermostat E and Nest Thermostat. What you see: a code.
Codes this page covers: N1 N2 N3 N4 N5 N6 N7 N15 N21 N22 N23 N24 N25 N26 N27 N28 N29 N71 N72 N73 N74 N75 N76 N77 N78 N79 N153 N156 N159 N261 N401 N402 N403 N404 N405 N406 N407 N408 N409 N411 N413 N414 N415.
What Google says to do
Wiring and power. Google ties this, on at least some systems, to the wiring, the power supply or the C wire. The steps here are only Google’s own, as its page states them; semiatic gives no wiring instructions of its own. Google’s own line on calling a professional is step 3 below.
- Google says to turn off power to your system at the breaker box, fuse box or system switch, pull off the display and check that every connector with a wire is pressed down, re-inserting any wire that is not.
- Google says there should be ⅓ to ½ inch of straight copper wire exposed, and the display should be pressed back on until it clicks before the power goes back on.
- Google says that if you still get the code but your system is running normally, you can dismiss the message and keep using the thermostat, though you may want a pro to check your system.
Source
Google’s own help page, read on the date shown.
- Google Nest Help: Troubleshoot Nest thermostat help codes — Nest Learning Thermostat (1st to 4th gen), Nest Thermostat E and Nest Thermostat; H codes only where a Heat Link is installed. support.google.com Checked 2026-09-29.