Warm air then cold air then warm air, etc

[jay_perry]

I’ve searched and seen a few similar questions but didn’t find any exactly on point (pardon me if I missed one). 

My HVAC, using the Nest Thermostat, heats just fine for several days then inextricably it starts blowing cool air, necesitsting the use of emergency heat (which works fine but is obviously super costly). Then after a few days I can turn emergency heat off and it operates normally again. Them cold air after a few days, etc. etc.  

I’ve had HVAC specialists look at it and they haven’t figured it out, although I’m not sure how familiar they are with the Nest Thermostat. 

Thoughts? 

[Markjosephp]

Hello jay_perry,

Thank you for reaching out and detailing the challenges you've been facing with your Nest Thermostat and system. I understand the inconvenience caused by the unexpected issue, and I appreciate your efforts in troubleshooting the problem. I'd be happy to shed some light on the situation here.

Do you have a Heat Pump system? If so, I did find an article to troubleshoot heat pump issues. Try to change its orientation and restart to refresh. Also, check for any wiring reports or message codes that would determine the possible cause, and gather the power readouts in the Technical Info settings or in the Equipment settings.

Let us know how it goes.

Best regards,
Mark