NEST Not Cooling — Install Issue, Blown Fuse / Shorted Circuit Board or Bigger Problem?

[Canes305]

I installed two NEST Learning Thermostats on July 4th weekend and by the next morning, my downstairs air was working fine, while upstairs hasn't blown cool since. (We had been out of town for a few weeks and ran out of time to fully deal with it, but we're home now and sweating.)

Some quick hits here:

— Units were installed in same fashion. Looking at side-by-side for WIRING in the app; Y1 (yellow) to cool, G (green) to fan, Rc (red) to power, W1 (white) to heat and 24V common (blue) to C. 

(Again, downstairs works and upstairs does not—so assumption is both were wired correctly.)

— One A/C repairman suggested a very common issue with NEST; a shorted circuit board or blown fuse in the circuit board. Seemed like an easy-enough fix, but he was booked for weeks so I brought out another tech and he said we could have a leak or blown furnace.

That said, upstairs air worked fine until we installed NEST; no cool air a day later. Convenient timing if something more catastrophic took place. Have to believe this was an install error, or ripple effect from install process. A leak or blown furnace the day after install is too coincidental. 

(Note: Killed all the power to the entire house while installing units, to avoid any blown fuses or circuit board issues.  Also, would a blown fuse or circuit board impact power? Again, the condenser it working outside, there is power to the NEST unit and air is blowing—it's simply not pushing cool air.)

The end result; we still have no cool air blowing upstairs since NEST was installed and I have a tech who feels it's an electric issue now booked up until September, while the cowboy who wants to tear up my attic and identify a leak, while replacing my furnace, can be over this week.

(This second gentleman also set up a device to measure levels on my outdoor condenser, while suggesting I properly clean all the coils—I did—while I also changed out the capacitor. Nothing helped, leading me to further believe it's a NEST issue, or a conveniently-timed disaster.) 

Whatever the case, we need our air fixed, need to troubleshoot this and would need to rule out user error or a NEST mishap before (potentially) getting taken to the cleaners by a non-tech-savvy tech who has completely dismissed a NEST issue and is calling for a leak or furnace replacement. 

Please advise. Thanks in advance for your time. 

 

[CBFox]

Three thoughts.

1.  Carefully examine the settings and the programming of your Nests to make sure that the upstairs one understands what you want.  In particular make sure that the upstairs isn't in Eco mode, and doesn't think that you're Away, and, most esoterically, isn't stuck on Safety Temperature.  (I'm assuming that you don't need help with programming but let us know if you're not sure.)

2.  Swap the two Nests.  Does the problem move downstairs or is it still upstairs?

2.  Before letting an expensive cowboy loose on your system, go buy the cheapest thermostat you can find that claims to be compatible with your system.  Does it work?

[Canes305]

Thank you for the thoughtful reply. 

— Regarding the programming, I am probably missing the boat there on some level, but everything I did downstairs I also did upstairs—and down worked immediately, while upstairs was immediately on the fritz. All and any initial programming suggestions are appreciated. 

— Out of town right now, but good call to swap the NESTs. Wish I'd tried that before leaving town. No-brainer troubleshooting effort I whiffed on. Will try when home.

— Per the last suggestion, the old thermostat worked fine and the day I installed NEST it went to hell in a handbag. Before buying and old thermostat and trying that troubleshooting process, would love to get someone in the know with NEST to troubleshoot for us (before letting the wild animal loose to tear up my attic and convincing me I need a brand new furnace.) 

Thanks again. All suggestions are appreciated. 

[peytbass]

I had the same issue with my Nest Learning Thermostat (only used one thermostat)after having been installed for about 60 days. The first time we had an a issue I called our local A/C company and the tech knew what to look for. The blown fuse you described on the HVAC circuit board. 20 minutes after the tech arrived and $149 later, I was back to the HVAC working. The tech suggested I look at another device as the Nest thermostats seemed to have this issue quite often. I contacted Nest and tech support escalated my case to the upper tier for a resolution. Nest surprisingly sent a check to me for the $149 service fee and exchanged the thermostat. Nice. The swap out lasted about 20 days and I had to call my tech back out. This time the tech was the most experienced of the tech and we discussed the issue at length and he suggested I go with a Honeywell or Ecobee. He had both in the van and we opted for the Ecobee. Since we were a regular customer he didn't charge us the service call, only the price of the thermostat and blown fuse ($3.50). It has now been 14 months since we replaced the Nest and we have not have any further issues our Goodman HVAC system installed in 2016. 

I've seen this same issue reported and discussed in other HVAC forums and it seems to be an issue for Nest. It's a shame as I really liked using the Nest thermostat.

[Markjosephp]

Hello peytbass,

Thanks for reaching out to the Google Nest Community Forum.

We deeply appreciate you sharing your thoughts and experiences using your Nest Thermostat, and we'll take it as feedback. We hope we can change your mind in the future so we can better look for its compatibility with your HVAC system.

Please let us know if you have any other questions or concerns. Otherwise, we'll lock this thread in 24 hours.

Regards,
Mark