Showing results for 
Search instead for 
Did you mean: 

Nest Learning Thermostat blinking green, blank display

Community Member

I'm installing a previously unused Nest thermostat, and when i fit the thermostat onto the base, the screen remains blank and  the LED at the top of the thermostat flashes green.  I initially waited over 30mins in case it was reloading software, but its now been in this state for over 12 hours.  I've removed and reinstalled it, confirmed that it sits on the pins correctly, and also held for 10 seconds until the LED flashes red, released, and repressed and released, but still the only response is the green flashing LED.  I've also removed it and connected directly to a power outlet via the mini-USB connection,  When i do this, after a couple of minutes the display shows a "home" image, and then directs me to reconnect it to the base.  However on reinstalling it to the base, I'm back to a blank screen and green flashing LED. 

I've got another Nest in the house and this works on either base unit without problem.  I've also checked the new Nest on both base units and i get the same green flashing light in both locations.

I've had the unit that isn't working for a few years, but its been in its original packaging the entire time.  I simply never got round to installing it, so suspect that the warranty has expired, even though its never been used!

I've looked at other posts, and see lots of similar examples of this problem, but I haven't found a post that recommends anything other than what I've already done.  Is there a solution to this  or some way of hard-setting the unit ?


Community Member

I having the same problem. My nest thermostat been disconnected from mains over summer unused now its just flashing green with a black screen. No idea what to do next 😕 

Community Specialist
Community Specialist

Hi everyone, 


Thanks for visiting the Community.


We apreciate all the details you've shared. A few things we'd like to ask-- can you tell us what type of thermostat are you using? Also, when did the issue start to happen? Lastly, can you tell us if you have tried any troubleshooting steps after you notice it?


We'd like to get more details regarding this so we can start some troubleshooting steps that might resolve this.




Community Member

Morning.Im using the elearning thermostat connected to mains. It was unplugged for a time over summer due to not needing it on and decorating work. When I plugged it on on Sunday all I had was a red light flashing. I took the front off then replaced it and the light went green. Stat stat still didn't work. Green light stopped working then and had nothing since. 

Fast forward to today and Boxt are on the way to replace it or repair whichever is doable. I'll let you know what they say 👍🏻

Community Member

Boxt came with a new heat link instead of a stat. They changed it anyway but thermostat still not working. App says error h27 dissconnected from power supply. Its clearly connected so Boxt will return with new stat on Friday.