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Fan runs randomly when unit is off

LindaF
Community Member

‎08-09-2023 08:54 PM

I have heat, no AC. I’ve had the Nest thermostat for almost exactly four years.

In the last couples weeks, the fan started running randomly running for a couple minutes at a time, usually around the same time and pattern. This week, it has started more often and for longer periods, up to continuously. The device and the app do not indicate the fan is running. I have to turn the fan on then off to shut off the erroneous fan. Even turning the thermostat to “off” won’t stop the fan.

I do have a C wire connected so I don’t know what could be the cause.

Any other ideas for resolving this?

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4 REPLIES 4

HVAC
Bronze
Bronze

‎08-09-2023 11:00 PM

Are you using in heat mode only & You’re not using or don’t have central AC!

If using heat only  a dirty filter & poor airflow will cause safety switches to turn off the heat and leave the fan running as a default mode. 
Much older gas fired unit don’t use circuitry so they act up also. 
check fan only schedule, cool to dry & eco options. Good luck 

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LindaF
Community Member
In response to HVAC

‎08-10-2023 09:11 AM

I do need to check my filter, but my Nest is actually turned to OFF 🤷🏻‍♀️

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HVAC
Bronze
Bronze
In response to LindaF

‎08-10-2023 09:15 AM

You can have the cool/heat feature to off but fan can still be on by itself just make sure it’s not on a set schedule of sort. Good luck 

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Jenelyn_O
Community Specialist
Community Specialist
In response to HVAC

‎08-20-2023 03:48 PM

Hi folks,

 

Thanks for reaching out. I'm sorry for the delay. Please remove your Nest Thermostat display from the base and wait about five minutes. 

 

If the fan turns off:

 

  1. Remove your C wire (ensure that the breaker is off before touching the wires).
  2. Monitor if the issue persists.

 

If the fan stays on:

 

  1. Shut down your HVAC system at the breaker box. Ensure as closely as possible that all power to the system is off before proceeding.
  2. Remove the wire connected to the G terminal (fan).
    Important: Any removed wire should not touch any other wire, especially not a power wire. Leave the wire sticking straight out and separated from any other wires before restoring power.
  3. Leave the thermostat display off the base.
  4. Turn the power back on.
  5. Wait for a maximum of five minutes to see if the suspected component still turns on and stays on with the display removed.

 

Let me know how it goes.

 

I appreciate your input, @HVAC.

 

Best,

Jenelyn

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