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Thermostat reading too high a temperature

Community Member

If your thermostat is reading too high a temperature, and you're powering it from an external 12v source, check that the source is DC not AC.   

I wired the thermostat to a handily located 12v doorbell transformer.   I wasn't aware, but these are generally AC, and observed the thermostat reading ambient + 5-6 degrees centigrade.  Surprisingly, in all other respects the thermostat worked fine.   On removing the thermostat from the base, the device was slightly warm.

Swapped to a 12v LED light driver and everything worked fine.


Community Specialist
Community Specialist

Hello somerando,


We value your time with us reporting your Nest Thermostat's erroneous temperature readings and your sharing of the steps you took to calibrate it. I wanted to be certain that everything went without a hitch.

Did everything go as planned after changing its power supply? From what country are you posting? Can you share with us your thermostat's signal strength value in its Technical Info settings under the Network option?

Let us know if you need more help.