Nest was working fine but now only blows out hot air

[MTkacsik]

I've been using my Nest thermostat for 6 months.    We used the Cool setting all summer with no issues and last month when it got cold we switched to Heat - no issues.    

Randomly yesterday I noticed it was hot in the house...like 78 degrees.   I switched to Heat and Cool to cool the house off and adjusted the temp appropriately but the heat continued to run.  We have checked the wires, done a factory reset, and all the recommended diagnostics and still we can only get hot air.   Why would this happen out of nowhere??  What can I do?

[Dadofbha]

Same problem.  Worked fine for a year now hot air only even when it’s supposed to cool.  Did all troubleshooting and no help.  

[4jay]

This is happening to me.  Ac worked before winter and heat worked.  Now turning on ac and system blows hot hot air like heater is on.  Any solution?

[CLJohnson8706]

Same issue - used from June 2021 to December 2021 with cooling.  Blew cold air fine.  Switched to heat in winter (January 2022 - today) blew hot air fine.  Even within the last week the the ac was blowing cold.  Now today it will only blow hot.  Checked wires, other troubleshoot items, checked outside unit, and still not working correctly.  Need a solution as it isn’t nice in Texas long.

[4jay]

Need a resolution as this is my 2nd one to do same thing before I change to another brand

[MTkacsik]

Hey all,

We ended up replacing the thermostat - still had the problem.   Had HVAC people out on Tuesday and it ended up that Nest wasn't the issue - reverse valve was stuck on our unit.   Apparently very common when switching from season to season.  Guy was here for 10 minutes and it was fixed.   Just paid for a service call and all is well now.   Was convinced it wasn't our unit because it's less than 3 years old, but turned out it was!  

[Daughter1]

I’m having problems with my nest thermostat