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Nest Learning Thermostat Cooling Mode Cycling Erratic

Community Member

Installed a new Nest Learning Thermostat last winter.  Propane furnace seemed to work fine.  Now with AC the cycles are erratic.  The condensing unit and the air handling unit run for a while, then the air handler shuts off but the condensing unit stays on.  The air handler comes on only after a minute or two instead of cycling off for a longer time.  The cycles when both systems are off are very short, one or two minutes, and then run for about 10 min.  I wonder if the new thermostat is causing the cycling errors.  Any suggestions or anyone having similar issues.


Platinum Product Expert
Platinum Product Expert

The thermostat is technically as simple device when comes to controlling your HVAC equipment.  For AC Cooling thermostat evaluates the temperature set point versus the ambient room temperature. If the ambient room temperature is higher than the set point, the thermostat initiates a call for cooling.  To do this the thermostat connect the R or Rc to the Y/Y1. This sends the input power (R) down the Y wire to the indoor air handler.  The air handler will turn on the blower fan, and Y wire is cross-connected to a wire going to the outdoor condenser unit and this will start the compressor. When the thermostats ambient temperature matches the set point, it deactivates the call for cooling by internally disconnecting R from Y. Now most air handlers will keep the blower fan running for an additional minute or two.  Now, if your system is cycling before the set point is reached, this indicates a problem with your outdoor condensing unit.  If the outdoor unit detects Low or High refrigerant pressure, the safety system deactivates the compressor to prevent damage.

Perhaps you need to call an HVAC company to come bay and tune your system up and provide a system cleaning.  

The AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

Hi there,

Thanks for reaching out. I hope  you get the answer you're looking for. You can visit this support article to find a trained HVAC pro to service your system.

I appreciate your help, @CoolingWizard.



Community Specialist
Community Specialist

Hi Papitorioseco,


I wanted to follow up if you still need help. Please let me know if you’re still having any concerns or questions from here, as I would be happy to take a closer look and assist you further.




Community Specialist
Community Specialist

Hey there,


I wanted to check in, and let you know that I will be locking the thread in 24 hours.


Best regards,