My 3rd generation Nest thermostat was originally set up without using the common wire. A few weeks ago it showed battery low and it shut off. I have other units in my house that use the common wire so I thought that could help. I had an HVAC technician out and made sure the common was available. The common was connected to the base and when the thermostat was connected it said the common wire was not connected. It was connected and the technician verified that there was a 24 volt circuit from the red wire to the blue (common) wire. The blue wire is connected to the base but the thermostat is not getting power from it. I switched the thermostat with one of my other units and it get the same error. Also, the "failing" unit works when connected to another base. It seems like the base is not making a connection between the wire connector and the pin connector. Like I said I had an HVAC technician check everything and he installs Nest thermostats. If I remove the common connector from the base I can get the unit to do basic functions but the battery is so low, it cannot connect to the network.
I wanted to stop by and see how I could help.
I appreciate your help here, Mel.
Thanks for letting us know, @WillieB. I'd love to know more about this.
Let us know how it goes.
The other thermostats are the same model and they do not get power thru the common on that base. They do get it on their own base. Also when I put the suspect one on another base it works. Before you ask, yes there is power on the Common. Had an HVAC tech double check.
Regarding the tech check, with the common connected to the back plate it shows that there is no power detected. So it sees that the wire is there but not detecting a circuit. Best I can tell the back plate has an issue.
Thanks for getting back to us and for updating us on what you've done to isolate the issue by swapping your two Nest thermostats. We'd like to take a closer look at this for you.
Please fill out this form with the needed information and let me know once you're done.