Nest thermostats suddenly no longer working

[AMCampos]

I installed 5 nests in my home 2 years ago. They were all connected to the heating unit with a very simple 2-wire connection (white to W1 and red to RH).

For 2 years they have worked flawlessly. At some point, however, during this summer, 3 of the thermostats stopped working. They stopped getting charged, and even when charged manually (using usb - something I never had to do before) they now indicate they lost connection to the unit - whatever that means. I measured voltage on the red wire for all 5 thermostats and they all indicate there is current (24v). The other 2 thermostats continue working flawlessly.

Has anyone seen this before? I had an electrician look at them and he was flummoxed. I am seeing winter coming, and getting a little worried. Thank you, hive mind!

[Jenelyn_O]

Hi AMCampos,

Thanks for reaching out. Nest Thermostats disconnect to the Wi-Fi if it experiences low battery issues. The wires connected to it should help the thermostat to fill the needed voltage to reconnect to the Wi-Fi.

I'd like to know more about it. A few questions: are all of your Nest Thermostats connected to the same HVAC system? How long did you charge your thermostat? Do your other thermostats have a C wire? Please provide your offline thermostat's power readouts. 

You can follow the guide below: 

1. Go to your thermostat Quick View menu.
2. Go to Settings.
3. Look for Technical Info.
4. Select Power.

Best,

Jenelyn