I have the 3rd generation of Nest Learning Thermostat. It has worked with no problems for a year or more. Recently it will stop waking when you walk up. No display at all. You can press the thermostat and it will show the display and you can control it normally. But after you walk away it starts doing this again. The App says the thermostat is not responding and I can no longer control it using the App. I read that it may need a C-wire, however I have not had a C-wire attached for the first year and a half of its use so why do I suddently need that to get it to charge up and work? This is frustrating since it cost so much. I see batteries for sale on Amazon that say they work with this model, but when I opened it up, the battery does not seem to be replaceable. It looks to be soldiered in and not removable. Am I forced to buy a new one every couple of years? If that is the case I will probably change to another brand that either has replacable batteries or gets enough power through the central heat\air system without anything extra.
