topic Re: Nest thermostat cannot turn off fan in Nest Thermostats

Nest thermostat cannot turn off fan

Krazrunner — Sun, 28 Nov 2021 15:31:16 GMT

My nest seems to be unable to turn the fan off. After running the AC last night, the fan did not turn off all night despite showing that the AC was only used for a total of 12 minutes. I know that the nest uses airwave technology but that would not cause the fan to run all night. Another common cause I’ve seen is that fan is set up to always on or some other schedule within the app. I’ve double checked all the settings and that is not the cause.

To test I’ve set the fan to run for 15 minutes from my phone within the google home app and the nest can turn on but when the 15 minute timer is up the fan does not shut off and the app does not show the fan to be running. All attempts to turn the fan off after that are unsuccessful. I tried manually setting the thermostat to turn on and off the fan again but the fan continues to run. The only way to turn the fan off is to turn off the breaker to the fan and unplug the nest from the hooks for 5 seconds. The same thing happens if I set a 15 minute timer from the nest itself, it will not shut off.

Has anyone else encountered this situation where the nest is able to turn on the fan but cannot turn the fan off? Any workarounds or suggestions?

Re: Nest thermostat cannot turn off fan

laurentbourg — Sun, 28 Nov 2021 16:36:14 GMT

Does your wire base have a connection to G? When the fan runs, if you just pop out the display base from the wire base does the fan stop or do you also need to shut off the breaker to the furnace?

Re: Nest thermostat cannot turn off fan

Krazrunner — Sun, 28 Nov 2021 17:09:49 GMT

Popping the display off of the base does not stop the fan. It has to be shut off from the breaker. It does have a connection to G. I’ll include a photo that shows the setup.

Re: Nest thermostat cannot turn off fan

laurentbourg — Mon, 29 Nov 2021 17:04:50 GMT

Typically popping the display should stop any ongoing relays, it is interesting you have to operate the breaker which would point more to a furnace issue where the internal low voltage to high voltage relay to the fan is faulty. Airwave should not be causing this like you said, but did you try disabling it just to make sure?

Re: Nest thermostat cannot turn off fan

laurentbourg — Mon, 29 Nov 2021 17:06:43 GMT

also is this a new install of the Nest or was everything working well previously and this problem suddenly appeared?

Re: Nest thermostat cannot turn off fan

Krazrunner — Mon, 29 Nov 2021 17:11:53 GMT

I’ll trial toggling off the airwave feature to see if that works. This is a new install of the nest.

Re: Nest thermostat cannot turn off fan

laurentbourg — Mon, 29 Nov 2021 17:16:49 GMT

Ok thanks, keep us posted.

Re: Nest thermostat cannot turn off fan

Krazrunner — Thu, 02 Dec 2021 23:17:11 GMT

Turning off the airwave has not improved the situation. A few times the fan has turned off at the end of the cooling session, but for the majority of times, the fan does not turn off after cooling and will remain on for hours even after the house temperature is less than the setting. The only way to turn it off is to turn off the breaker. Even turning the fan on and off via the nest device or the google home app is unsuccessful. The fan will turn on when I set it to but when I turn it off it will not. I’m a loss of how to proceed because running the fan 24/7 is not an option and I cannot leave on vacation with the nest because if the fan ever does turn on it will remain on for the rest of the time I’m away as I won’t be there to shut off the breaker.

Re: Nest thermostat cannot turn off fan

laurentbourg — Thu, 02 Dec 2021 23:20:14 GMT

Thanks Krazrunner, we will get there. Next thing is to make sure that the interpretation of Nest matches your physical wiring, can you please post a screenshot of the wiring in the google home app, you can access it in the settings -> Thermostat -> Wiring

Re: Nest thermostat cannot turn off fan

Krazrunner — Fri, 03 Dec 2021 00:20:58 GMT

Re: Nest thermostat cannot turn off fan

laurentbourg — Fri, 03 Dec 2021 01:01:07 GMT

The wiring diagram is correct. Is it easy for you to exchange the Nest or try another brand new Nest and return this one if the issue gets resolved? Isolating any relay issue is preferred here. It is possible that your Nest is defective, and that the fan relay stays open despite the fan attempting to close it, until at some point it just closes itself, which can be random on when that happens. Alternatively that could be an issue on your furnace, but I don’t think that’s the case since everything was working well until recently.

Re: Nest thermostat cannot turn off fan

Stella — Wed, 12 Jan 2022 07:30:08 GMT

Hello any udpates on the post? I experienced the same issue.

Re: Nest thermostat cannot turn off fan

Krazrunner — Wed, 12 Jan 2022 20:12:18 GMT

After trying all I could as documented above, I chatted with google support but ultimately could not come up with a solution and returned the device. I did learn that not all AC/heating units that say they are compatible based on the wiring are actually compatible so if you know your model number I would chat with google support to see if it is compatible before moving forward.

Re: Nest thermostat cannot turn off fan

wangkuo — Thu, 20 Jan 2022 16:22:56 GMT

I have a same problem with a new nest learning thermostat. Based on your comments, I think I need to return the device. Thank you so much.

Re: Nest thermostat cannot turn off fan

Jessup — Wed, 09 Feb 2022 19:32:03 GMT

My nest wont even allow me to turn off the fan. Not sure what the problem is.

Re: Nest thermostat cannot turn off fan

Haze1 — Fri, 04 Mar 2022 19:44:04 GMT

I’m experiencing the same problem. The fan just won’t turn off.

Re: Nest thermostat cannot turn off fan

DC1984 — Sun, 13 Mar 2022 22:35:31 GMT

Same problem here… can’t find a solution anywhere.

Re: Nest thermostat cannot turn off fan

Ilter15 — Sat, 26 Mar 2022 15:52:04 GMT

I am having the same issue. Having to turn off from the breaker every time. Google support??

Re: Nest thermostat cannot turn off fan

Ilter15 — Sat, 26 Mar 2022 15:53:44 GMT

I've had the nest for over a year and never had a problem before this..

Re: Nest thermostat cannot turn off fan

DC1984 — Sat, 26 Mar 2022 16:23:55 GMT

Found my problem! My previous thermostat mounted to the wall via screws on the left/right sides of the mounting plate. The nest mounts via screws on the top/bottom of the mounting plate. When I set those screws, I unknowingly hit the wiring causing a short. I moved the thermostat over 1/2” and that solved the problem.