Nest Thermostat heats for 59 seconds

[Jasonmack5]

Thermostat has been installed and working properly for a couple of months. 

Replaced the batteries today and it worked fine for a few hours. 

Now it will only heat for 59 seconds, goes back to “starting soon” for 2:30, and repeats the cycle over and over. 

I’ve powered it off and on, and pulled the batteries to try to reset it. Nothing works….

[Jasonmack5]

Performed a factory reset with no luck. 

Cut power to heat pump at the breaker and turned it back on with no luck. 

I’m out of ideas. Hoping someone here has an answer. Odd that a practically new thermostat that’s been working perfectly would just take a dump. 

[Markjosephp]

Hi Jasonmack5,

Thank you for taking the time to let us know about your inquiry.

It's indeed strange that a recently installed and well-functioning Nest Thermostat would suddenly act up. You've already gone through some troubleshooting steps, and it seems like you're doing everything right.

Since you've performed a factory reset, cut power to the heat pump, and tried other basic troubleshooting steps, it might be worth checking if there's a wiring report or message code on its settings. You can gather its power readouts in the Equipment settings, as the short cycle indicates a power-related issue. Also, does it have a C-wire? This would bring constant power to the thermostat and avoid power issues.

Please check out this article to learn about the common or C wire. Let us know if you have more questions.

Regards,
Mark

[Jasonmack5]

Update:

The heat pump had an internal wiring issue. A wire had rubbed on the housing, causing a short and blowing a fuse. Obviously this was no fault of the thermostat.  

BUT….. the function of the thermostat in this situation is frustrating. Rather than giving an error code, it constantly tried to run the unit, cycling it on every 3 minutes. Because we were in & out of the house & didn’t notice it for a while, it cycled 40 times before I started diagnosing it. 

No reason the thermostat can’t be “smarter” than that….

[Markjosephp]

Hey there,

It's indeed unfortunate that the internal wiring problem led to a short circuit and fuse blowout, and it's good to know that you identified the root cause. I understand that it didn't provide a more helpful error code or halt the cycling after a certain number of attempts. It's worth checking the HVAC monitoring from the Google Nest article that can help you identify if a potential issue is detected. We'll send you an alert via email or an app notification.

Let me know if you have more questions or need more help—we're always here.

Warm regards,
Mark