My Nest Thermostat is Model 1.4 Serial Number 64166600645DADC9, software version 2.2-6, interestingly updated Dec 31, 1969. (Not sure Google existed at 1969)
This thermostat can not maintain a comfortable room, either it is cold or hot, this happens in both heating and cooling modes. Had this for a few years and put up with it, ready to pitch it. I am retired so I removed all of the schedules still the same problem. I have worked as an Engineer with a temperature control company but this thermostat is junk, only good thing about this unit is easy to setup and remote access to the device.
