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A continuously running blower fan in an HVAC system may suggest an issue that needs addressing. Typically, these systems initiate the fan only at the commencement of a warming or cooling phase. The fan is designed to automatically stop working once the target temperature is reached.

So how can you fix a fan that won't turn off? In the steps below, I’ll show you how. 

Step 1: Try Manually Adjusting the Fan Settings

In case you're running into connectivity issues with the Google Home or Nest app, I highly recommend controlling the fan directly via the thermostat controls. 

This helps you skip over any Wi-Fi delays and glitches, controlling the fan right from the source. 

Adjust Fan Settings on the Nest Thermostat

Manually change fan settings on the thermostat display

Nest thermostats three models 1 1
  1. Wake up the thermostat by pressing the device/ring button
  2. Then, open the Quick-View Menu and cycle to the “Fan” settings (represented by a fan rudder icon)
  3. If you have the option to “cancel” select that option (highlight this option using the dial and press into the thermostat to confirm)
  4. However, if your fan is still running, but the thermostat shows the option to “Turn on” the fan, you can try that.
  5. Simply follow the thermostat’s instructions: rotate the dial to confirm the duration for the fan
  6. The lowest value is usually 15 minutes, turn the dial to that value and press the thermostat to confirm
  7. Then, time the 15 minutes, and see if the fan turns off. 

Usually, this will clear out any glitches and restore the fan’s connection with the thermostat. However, if this didn’t resolve the issue, you might have to start the second process of elimination: the thermostat. 

Throughout this process, you might have to troubleshoot the wiring or check the power to the HVAC equipment. So make sure you follow the necessary safety precautions such as turning off power to the thermostat before handling the wiring. 

If you're not comfortable troubleshooting these yourself, I highly recommend you skip these steps and get help from a professional instead.

Step 2: Remove the Thermostat from the Wall

To make sure the thermostat is not the root of the problem, it’s important to see if the blower turns on even when the thermostat is disconnected. 

To carry this out:

  1. Remove the Nest thermostat off the wall mount
  2. If you switched off power to the thermostat previously, restore power and see if the blower stays on without the thermostat on the wall.

If the blower fan keeps running, even after you’ve removed the thermostat display from the wall mount, then it’s definitely a wiring issue or a fault with the HVAC equipment. 

If so, you can skip to step 8 of this guide.

However, if the fan powers down, after you remove the thermostat, this means the Nest thermostat is faulty. In most cases, this might be due to specific settings or software issues. 

So keep troubleshooting with the next step.

Step 3: Restart the Thermostat

One of the fastest methods to resolve software issues or glitches in a Nest thermostat is to restart it. Here’s how:

  1. Open the thermostat and head over to “Settings”
  2. Then, navigate to “Reset”
  3. Select the option to “Restart”
  4. Then provide any confirmations 
  5. Wait until the device reboots, then check if the fan powers down
  6. If not, try adjusting the fan manually, similar to the step mentioned above. 

However, if the screen is not responsive, you can force-shutdown the thermostat by holding the ring button for ten seconds and pressing it again to turn it on. 

Step 4: Update the Thermostat

If the thermostat is pending updates, letting it update to the latest firmware might help fix the issue. 

Google is always rolling out new software updates that help fix common bugs and certain glitches. So if you have an update available, it's best to update. 

Usually, your Nest thermostat updates itself automatically over Wi-Fi. 

However, in case you’re keeping it offline, or you missed the update, you can still manually command the thermostat to check for updates and download any, if available. 

To check for Updates in the Nest Thermostat (2020 Model)

  1. Wake up the display and open the Quick-View menu.
  2. After that, head over to “Settings”
  3. Then, head over to “Version”
  4. Select the option to “Update”
  5. However, make sure the thermostat is reconnected to the Wi-Fi

Manually Update Nest Thermostat E and Learning Models

  1. Head over to “Settings”
  2. Navigate to “Software”
  3. Select “Update”

Step 5: Clear the Schedule and Disable Automated Features

In some rare instances, the schedule and automated features, such as Home/Away Assist might be interfering with the device. 

Therefore, I recommend clearing the schedule and disabling these features to see if you can wrestle fan control back from the device.

For exact details on this process, check out this article. 

Step 6: Disable Nest Sense Features

Apart from clearing up the schedules and disabling the automated features, you can also try to disable Nest Sense features. 

These include functions related to the air conditioning system such as Airwave and Cool-To-Dry. (Native to the Nest thermostat E and Learning models.)

These couple of features, although have minimal impact on the cooling and blower equipment, tend to control the air conditioner and blower fan during certain scenarios (such as low humidity), so disabling them can help get the fan back on track. 

Disable AirWave and Cool-To-Dry On the Thermostat

  1. Head over to “Settings” on your Nest thermostat
  2. Then, scroll to “Nest Sense”
  3. Select Airwave or Cool-To-Dry
  4. Select the setting to “Turn Off” each of these features, one by one.

Disable Nest Sense Features Via the Nest App

  1. Open the Nest app and select your thermostat
  2. Then, head over to “Settings” on the Nest app (typically located in the upper-right corner of the screen)
  3. Scroll to “Nest Sense” or select the option for “Airwave” or “Cool-To-Dry”
  4. Enter each sub-menu and toggle them to the “Off” position.

After disabling these extra features, try to check the fan control again. 

Step 7: Disabling Fan Settings For the HVAC Equipment

Reconfiguring the fan settings for the heating and cooling equipment might also help clear out this issue and get your system back in order. 

However, only follow through with this step, after you’ve determined the cause to be the thermostat and not the wiring and HVAC equipment.

To reconfigure the equipment on the thermostat:

  1. Open the settings and head over to “Equipment”
  2. A diagram indicating the thermostat wiring will show up. 
  3. Here, check to see if the “G” wire is detected and take a photo of this diagram. This will serve useful when troubleshooting the physical wiring later on.
  4. After that, select “Continue”
  5. The available system modes for your HVAC system will show up, check to confirm that “Fan” is displayed on this list. Then, tap on “Continue”
  6. After that, scroll to “Pro Setup”
  7. Select “Continue”
  8. The wiring diagram will show up again, now indicating the detected wires in green. Also, here, note down if the G wire is colored green, grayed out, or yellow.
  9. Then, scroll to select each wire in your setup. Select the Y or W wires and press the ring button to customize its settings.
  10. A list of options will show up. Here, scroll to highlight “Fan” and select it to change its settings. 
  11. Adjust it to “Don’t Activate.” Then, press the ring button to confirm this change.
  12. After that, tap on Continue to return to the wiring menu. 
  13. Follow steps 10-12 for all the available wires.
  14. Then, select “Done” to exit the equipment menu and follow the thermostat instructions to return to the home screen.
  15. Finally, adjust the temperatures manually and see if the fan stays powered down. You can restart the thermostat to ensure the settings take effect. 

Step 8: Check the Wiring

If any of the above solutions didn't fix the issue, it’s time to check the wiring. 

For this type of issue, the fan might stay on when it’s damaged or maintains a short connection with any of the other thermostat wires. 

Troubleshooting any short connections is pretty straightforward, but you need a multimeter to carry this out. So if you don’t have one already, or don’t feel too comfortable troubleshooting the wires, now might be a good time to call in the professionals. 

Anyhow, to check the wiring on your Nest thermostat:

  1. First, turn off the power to the thermostat and the HVAC system
  2. Then, take out the thermostat display off the wall mount
  3. Check the wiring connections. Make sure the G wire is installed separately, in its assigned terminal. 
  4. You can pull up the photo of the wiring diagram you took in the previous step, and check to see if everything’s installed as it should be. 
  5. If you notice any splice connections or damage to any of the wires, make sure to address them accordingly. The connections should be properly isolated and tightly secured. 

To Check for Any Short Connections (Using a multimeter):

  1. Take out the G wire from the Nest thermostat’s base plate
  2. Then, take out the R wire
  3. After that, take your multimeter and adjust it to either the resistance or the continuity setting (diode symbol with an alarm)
  4. Then, connect one probe of the multimeter to the G wire and the other to the R wire.
  5. Check to see if the multimeter puts out a beep or a low resistance reading
  6. This would indicate a short circuit between these two thermostat wires.
  7. However, if the R and G wires do not have a short connection, try measuring for a short connection with the G wire and the rest of the thermostat wires. (Such as the Y, W, and C Wire).

If you find any short connections, you might have to check the entire length of the thermostat wire or where the other end connects to the furnace control board or your HVAC system. 

This tends to be a complicated process, so it’s best to get help from a professional.

Step 9: Troubleshoot the C-Wire

For most Nest thermostats, the C-wire plays a fundamental role in improving power stability and resolving any glitches. So if you don’t have one already, it’s better to consider installing one

So fix up the C-wire to your thermostat and see if this takes care of the problem. 

That being said, if you have one installed already, removing the C-wire, and checking for fan operation, is also worth a shot. However, don’t forget to turn off the power before you remove the C-wire. 

Step 10: Factory Reset the Thermostat

A factory reset, on your Nest thermostat, might help clear out any lingering glitches or conflicting settings. 

This is the ultimate fix, especially after you’ve deduced the culprit to be the Nest thermostat.

However, a factory reset is kind of a last-resort solution since it will delete your schedule and any other custom settings. 

So before you follow through with this, make sure to note down any important settings and equipment configuration options. 

Then, check out this article on the exact steps on how to factory reset your Nest thermostat. 

Final Step: Check the HVAC Equipment or Call in the Cavalry

When the problem is the blower fan or the HVAC system, factory resetting your Nest thermostat won’t fix the issue. 

The issue may lie within the HVAC equipment, with issues such as:

  • Fan limit control issues (in older furnaces) 
  • A blown fuse
  • Problems with the sequencer
  • A malfunctioning or stuck high-limit switch
  • Tripped flame rollout 
  • Tripped low-pressure gas switch, 
  • Issues with the blower motor

As you can see, troubleshooting these is not an easy task for the regular consumer. Therefore, I highly recommend getting help from a certified HVAC professional. 

Wrapping Up

A blower fan that runs continuously can wear down the equipment faster and consume a lot of electricity. So to avoid sky-high energy bills and inefficient temperature management, it’s best to troubleshoot and get the fan back under control. 

Make sure to go through the troubleshooting guide above and drop us a comment if you run into any issues.


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