Nest thermostat cannot turn off fan

[Krazrunner]

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?

[laurentbourg]

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?

[Krazrunner]

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.

 

[laurentbourg]

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?

[laurentbourg]

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

[Krazrunner]

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

[laurentbourg]

Ok thanks, keep us posted. 

[Krazrunner]

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. 

[laurentbourg]

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

[Krazrunner]

 

[SelmaTeacher7]

Same issue here. Is it a bug?  I have the same problem, where the fan is on all of the time.  I checked the wiring, it is correct on both the plate and in the app, I followed the steps as you have directed to the other customer.  The fan comes on when power is restored and will never go off.  

[Peton22]

The fan keeps running.

[joeybags]

fan does not turn off

[laurentbourg]

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.  

[Clmk]

Mine is doing the same thing.  New just out 5 months ago and have had issues ever since.  Fan doesn't turn off. 

[Kenadian]

You have a shortes back plate that need to be exchanged for a new one. That was the issue with mine, fixed the problem immediately upon replacement.

[Artcard]

What is a shortes 

[Stella]

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

[Krazrunner]

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. 

[wangkuo]

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.

[Jessup]

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

[DougDan]

I’m having the same problem, fan will not turn off. 

[Haze1]

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

[DC1984]

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

[Ilter15]

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

[Ilter15]

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

[DC1984]

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.

[BarryO]

Same issue here but in my case I’m already out of town. Hope my fan does not burn out.

I have the E model installed at this house (recently) - which is one of two of my Nest thermostats. The older thermostat (in a different house) has never had a fan problem.  I am thinking there may be a bug in the Nest software.  I have also noticed that the app is not updated frequently. Thanks 

[Hannahatenest]

I’m having the same issue. My bill is high because it runs all the time even if I have turned it off. 

[kdawn8000]

I am having the same issue and can not turn the fan off remotely. 

[Tonyz]

Same issue here. Is it a bug?

[sodope99]

I found a solution for my fan running constantly whenever the unit is on. Hope this can help some of you...

I set the AC to one degree below the actual temp to activate the system, and then immediately set it back to my Eco setting a few degrees higher - the fan turned off when the AC did and it hasn't turned back on since. 

This is how my problem started in case someone is in a similar situation:

I've had my unit for about 4 months and never had any issues, even when manually running the fan. I recently left town for an extended trip and turned on the fan schedule to run once a day to circulate the air since the temperature wasn't reaching either Eco temp - I did this remotely from the app about a day after I left home. I checked back later that day and the fan was still on. I tried turning the unit off and on, but the fan always turned right back on with it even though it wasn't heating or cooling. It stayed on for a couple more days while I tried to find a solution, and I was manually turning the unit off and on to prevent the fan burning out in the meantime.

[JoeyQuantum]

I had the same problem. Fan will not shut off. Even after AC was on and then AC shut off fan would turn off for about 5 seconds then turn back on and run constantly. The only way I could shut off the fan was to pull the nest thermostat off the Wall then it shut off. I reverted back to my old Honeywell everything worked fine. It's got to be a problem with the nest firmware or something. I'm returning it to home Depot today and stick with my old Honeywell which work perfectly fine.

[medina80]

I have an old 2nd generation that is supposed to work with Alexa. Not sure how I activate that function. My fan keeps turning on and runs for several hours every day. The compressor is not running because I can look out the door and see that. Have tried all the suggestions and still have the problem. I am thinking about removing the Nest and going back to old thermostat. Don't want to do that since I have had it for many years. I am retired so being able to set a schedule is not an important factor. I just want it to stay at a temperature I set until I manually change it and I don't want the fan to run if the compressor isn't running. Is that too much to ask???

[Marizzle87]

Same issue my fan won't shut off and the lines are getting iced up as well. 

Had an AC tech come out and he couldn't figure it out. 

Anybody have a solution? 

[Spshish123]

I have same issue. Somehow when switched to older battery model the fan turned off. 

[Stigger357]

I just noticed this same issue yesterday. Fan never shuts off unless i pull nest from the wall and turn off the breaker. Checked all settings, wires, i have had it for two months, so upsetting, going to have to send it back.

[Hannahatenest]

It’s sad. Nest isn’t our friend.

[Stigger357]

After posting here, now my nest is back to working like it should, have not changed a thing. 

[Somekindabonita]

We're having the same issue.  Nest has been installed for over a year and it just started happening recently.