I have this weird issue. I own 2 Nest thermostats, one model 3 and one model 2. Have been using them for many years with no big problems. Now, when the temperatures get colder, I started using the heating and that’s when I started experiencing a problem with the Nest model 2. When I changed the modus to ‘heating’ it works fine for about 5-7 minutes and then it turns itself ‘OFF’. I can change the modus to ‘heating’, but every time it turns itself ‘OFF’.
Yesterday I disconnected everything (Nest App/Google Home and The Nest Integration in HA) and then the thermostat worked fine and stayed on ‘heating’. Then I added the thermostat to the Nest App/Google Home and that worked also as expected. But when I added the thermostat to Home Assistant via the integration, the thermostat turns itself OFF in 5-7 minutes. Now I have deleted the Nest integration and it is working fine again. With the other thermostat (model 3) there are no problems at all. I don’t know how to solve this weird issue and was hoping someone could help?
Is there any information in the HOME ASSISTANT LOGBOOK related to this unwanted behavior? If an error occurs in/with the Nest integration in HA then there could be some info in the LOGBOOK.
Hi,
Can’t find any entry in the logbook related to the Nest integration or the thermostat entity (climate.zolder). Is there a way to see more details for a specific entity?
Because the problem seems to be with the Integration, I checked all steps to create and configure a Google Cloud Project and also made new credentials. Added the Nest Integration again. It took about 10 minutes and the thermostat went OFF again 
I deleted the project in Google cloud and made a new one with new credentials, etc. No luck, thermostat went OFF again after a few minutes. So the Nest thermostat in the Nest App gives no problems and I have also no problem with the Nest thermostat in Google Home. Only when I activate this thermostat (model 2) in the HA integration. The other thermostat (model 3) functions well in Home Assistant.
I couldn’t believe it was a problem with the thermostat itself. So I already figures out that it had to do something with Home Assistant but could not figure out what exactly. I use Proxmox and have a container for Node-Red only so it was easy to shut that down. And the thermostat stayed ON 
So the problem was in the Node-Red automations. I searched for all nodes with ‘thermostat’ or ‘nest’ in it and disabled those. After starting Node-Red again the thermostat sayed ON. Checked all those nodes and found 3 of them that could cause problems. Fixed those and the problem was gone! Happy again 
Nice, good job!