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Nest thermostat loss of power e102

Community Member



I have a 4 wire system.  The thermostat worked fine for AC.  


Had a chilly but decent day today to burn off summer, lol.


Clicked on the heat, and I seemed to only have partial power?


The regulator was snapping back into place instead of staying open.  


I am a hoarder so I still had my old analog one, and reinstalled that problem solved.


Any idea how to switch back to the nest?


Community Member

I seem to be having a similar issue. Only on heat works fine with ac. My furnace will run but shuts off multiple times a cycle saying power loss. Going to look more into it this weekend. If I figure it out I'll be sure to let you know. 

Community Specialist
Community Specialist

Hi everyone,


Thanks for being here in the Google Nest Community.


@MikeB14, could you share a photo of your current wiring configuration? @Ryanb2012, do you have a C wire connected to your Nest Thermostat?


Based on the details from your posts, it looks like your system is having some power issue. It's possible that your Nest Thermostat is not getting enough power from the HVAC unit.




Community Member

I had to switch back to my old thermostat as it is in the 40s here at night.  When I had the nest installed, I used Rc (tried swapping to Rh to see if the internal jumper was bad), w1, g, y1.  I hope this helps.  Furnace workes fine with olf thermostat so should be an in house issue? 


Sorry about the ugly wall, im refinishing the plaster walls.


Community Member

It was in fact the common wire. Luckily I had 2 extra wires in the wall and connected one to constant and it fixed the issue.