topic Re: Nest Learning thermostat e79 after power outage in Nest Thermostats

Nest Learning thermostat e79 after power outage

blphilli — Sat, 24 Dec 2022 18:34:19 GMT

Have two new learning thermostats installed working fine. A couple days later, we've had intermittent power failures due to high winds in the area- one lasting an hour, others only briefly. The thermostats stopped operating the furnaces and presented code e79 (no power to common). Checked wiring, everything is fine. when replacing the thermostat, it corrected itself. That's fine, but I need confidence the system will reset by itself if the power goes off while we are not home in the winter. Followed the instructions for install. Only thing to note was the instructions indicated to Not use any jumpers. The previous thermostats had jumpers connecting RC and R.

Re: Nest Learning thermostat e79 after power outage

Jhonleanmel — Wed, 28 Dec 2022 18:26:00 GMT

Hi blphilli,

Thanks for posting.

Your Nest Learning Thermostat should be back and working once the power comes back from an outage. It may take time for the device to fully boot up.

Thanks,

Mel

Re: Nest Learning thermostat e79 after power outage

nogoodusername — Thu, 29 Dec 2022 23:52:59 GMT

Since this isn't closed, I wanted to ask the same sort of thing. I've had my Nest learning thermostat since 2017, no issues. Power went out twice in the last 5 days due to high winds, Nest is not responding. Flashes red light indicating that it's charging. I pulled it off and hooked it up to USB, when it says to replace it, I do. I noticed voltage is at 3.47 or thereabouts (I know this is too low). Would leaving it on USB for an hour fix this? It keeps telling me to put it back!

Re: Nest Learning thermostat e79 after power outage

nogoodusername — Fri, 30 Dec 2022 23:58:42 GMT

Figured out the solution -- I left the thermostat on a powered USB for 12+ hours. Works fine now. I guess even when it says "put me back on the wall" it may not have enough power!

Re: Nest Learning thermostat e79 after power outage

Jake — Tue, 03 Jan 2023 23:08:15 GMT

Hey there,

I am glad to hear everything is good to go, and the device is working. I am going to go ahead and leave the thread open for 24 hours in case you have any further questions from here.

Best regards,

Jake