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Nest Thermostat Keep turning on/off every 30 seconds

Community Member

I’m having problem getting my Nest Thermostat Gen3 working properly. After wiring everything, the thermostat functions properly with the exception of 1 problem.

After the house reaches the desired temperature from the heating unit (66F), every 30seconds or so I hear the HVAC unit turn on for maybe 5 seconds and then turn itself off. What am I doing wrong? If i install the old thermostat back, everything works back to normal again. No on/off problem. The old thermostat unit doesn't have the Blue cable connected.

I have tried

  • Unplug the wire, insert back in to the nest unit, factory reset
  • removing green wire (fan) from the nest unit and connect the yellow and green together on hvac using thermostat cable, but the problem still persist.

My wiring is as follow. Line colors are the actual color of the wire. I am running gas to heat (Forced Air i believe)

Screen Shot 2022-03-28 at 6.50.23 PM.png


Platinum Product Expert
Platinum Product Expert

Post a picture of the original thermostat's wiring here

I don't see a C wire in that picture, where did it come from?


The C Wire wasnt used in the old thermostat. I first tried without the c wire with nest, but then it kept turning the hvac on and off every 30 seconds. Read online and people say it's because it needs the c wire. So i use the c wire, and it was detected by nest just fine, but the problem still persists. 

Community Specialist
Community Specialist

Hi russeldawson,


Thanks for reaching out and we're sorry to hear about what's happening. 


Other than the C (common wire), we should also check the equipment selection and make sure that we've chosen the right heat type and source. Go to settings > equipment > select the right heat type and source then test your equipment.


Thanks for your help, Patrick_Caezza.


Let us know how it goes by replying to this thread.


Best regards,



I did that as well. I picked forced air, which is what I have. it didn't solve anything. 

Community Specialist
Community Specialist

Hey folks,


Thanks for visiting the Google Nest Community. 


Since this thread hasn't had activity in a while, we're going to close it to keep content fresh.

If you have additional questions, feel free to submit another post and provide as many details as possible so that others can lend a hand. 


Hope this helps!


Kind regards,



Platinum Product Expert
Platinum Product Expert

Your wiring is correct for a conventional system which it appears that you have.


Try doing a factory reset to default and setting it up again.

I did that several times. With the c wire and without the c wire. The problem persist. Is it because of faulty nest?