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Addressing problems linked to a faulty Nest thermostat can be quite difficult. The situation may notably complicate when facing issues such as a continuous blinking of the green light, unreliable HVAC management, or a completely unresponsive screen.

The flashing green light communicates that the Nest thermostat is undertaking a software/firmware update (or the device is starting up, or restarting). It generally lasts a minute which is normal, however, if it won’t go away then you have a problem.

In this article, I dive into 11 ways to fix the flashing green light on your Nest Thermostat.

What does the flashing green light on a Nest Thermostat mean?

A flashing green light on your Nest thermostat signifies that the device is undergoing a software/firmware update, is starting up, or is restarting. These processes are essential to ensure that your thermostat stays up-to-date with the latest software features and improvements.

However, there are instances when the thermostat might become unresponsive due to issues during the update process.

If you notice that the green light continues to blink for more than 15 minutes and the thermostat remains unresponsive, it's possible that the device has frozen during the update. 

In the following sections, I explore 11 steps to troubleshoot and fix the Nest thermostat blinking green light issue, helping you restore your thermostat to its normal functioning state.

Nest Thermostat 1

11 Steps to Fix the Flashing Green Light

Check out my 11 simple steps to troubleshoot and resolve the annoying blinking green light issue with your Nest thermostat below.

1. Manually Fully Charge the Device

Manually charging your Nest Thermostat is essential in resolving the blinking green light issue, as low battery levels can cause unpredictable behavior.

  1. To do this, first, remove the display by gently pulling it off.
  2. Identify the appropriate USB cable for your thermostat model, which will either be a mini or micro USB.
  3. Keep in mind that using computer USB ports or unpowered USB for charging may not deliver adequate power to your device.
  4. As soon as charging begins, the thermostat screen will illuminate and prompt you to reconnect the device to its base.
  5. Place your Nest Thermostat back on its mount and apply light pressure until it clicks, signifying proper reattachment.

Also, double-check the functionality of the power adapter you're using; test it with another device, or try a different one with your thermostat to ensure optimal charging.

Nest Thermostat Pins

2. Reconnect the Display to the Base

Now it's time to try reconnecting the display to the base.

  1. To do this, carefully remove the display by pulling it straight off the base.
  2. Before reattaching it, examine the pin connector to ensure it is aligned correctly. It's also a good opportunity to inspect the 20-pin connector.
  3. When you're confident that the alignment is right, push the display back onto the base.
  4. You'll know it's securely in place when you hear an audible click.
  5. Look for any signs of visible damage that could be causing the green light to blink.
  6. If you don't find any issues, you can proceed to the next step.

3. Manually Trigger the Software or Firmware Update

A blinking green light on your Nest Thermostat typically indicates it's carrying out a software or firmware update.

However, if the light continues to blink for a prolonged period without any response from the device, it's possible the thermostat has frozen mid-update.

Some updates can be extensive, causing the green indicator to flash for over 30 minutes.

To address this issue, open the Nest app on your smartphone to check for new updates and monitor the device's update progress.

You can view a history of the latest software updates for your Nest thermostat on this page. Then you can compare it to what you have on your thermostat by going to Settings > Software / Version > Update.

Circuit Breaker

4. Double Check the HVAC Power Supply

A blinking green light on your Nest Thermostat can indicate an insufficient power supply from your HVAC system.

Begin by ensuring your HVAC system is completely powered on. Next, inspect your home's circuit breakers to identify if any have tripped.

Resetting a tripped breaker can help restore the correct power supply to your Nest Thermostat.

5. Restart the Nest Thermostat

Restarting the device is one of the easiest ways to resolve this problem.

For Nest Thermostat E or Nest Learning Thermostats: 

  1. Press down the thermostat for 10 seconds to turn off the screen.
  2. Press and release the ring to restart the thermostat and wait for the Nest logo.

For Nest Thermostat (Older model): 

  1. Detach the thermostat from the base.
  2. Remove the AAA batteries.
  3. Reinsert the batteries and attach the thermostat back to its base.
Nest Reset

6. Reset the Nest Thermostat

If a restart doesn’t work, then you can revert the thermostat back to factory settings.

  • Go to Settings and then Equipment to note down necessary wiring information.
  • Choose Restart or Factory Reset from Settings, confirm your choice, and wait for the thermostat to restart or reset.
  • If you have a Nest Thermostat E or Nest Learning Thermostat, go to Settings, then Reset, and choose between Restart, Schedule, Home/Away, Account connection, WWN Connection, Network, or All Settings (restore to factory default).
  • Reconnect your thermostat to the app, and allow it to learn about your home and schedule again.

7. Double Check the Wiring

Sometimes, a blinking green light on your Nest thermostat may simply be due to improper wiring.

If the wires aren't correctly in place (particularly the R and C wires), the thermostat could act strangely, like flashing a green light.

To fix this issue, first, remove the thermostat display from its base, ensuring that the wires are flat and properly positioned on the base.

Next, turn off the power to your HVAC system, and carefully reseat all the wires.

It's crucial that the wire from each terminal is flush against the base to ensure the display seats correctly.

Finally, turn the power back on and reattach the display to the base.

Examining and securing these wire connections can help your thermostat function more effectively and stop the blinking green light.

8. Double Check your Wi-Fi

A disrupted network connection during a software update might lead to your Nest Thermostat's green light flashing.

To rule out this possibility, ensure that your Wi-Fi is functioning properly.

If you detect that your Wi-Fi or internet is down, focus on troubleshooting your router to restore the connection and resolve the issue.

In some cases, the best course of action is to reboot your router by unplugging it for a few moments and then plugging it back in.

Once your internet connection is up and running again, observe if the Nest Thermostat's blinking green light stops.

If it doesn't, there may be a different issue at play, so keep proceeding through the remaining steps to identify and fix the problem.

Nest Thermostat Wiring 1

9. Hook up a C-Wire

For a steady power supply, it's often beneficial to hook up a C-Wire to your Nest Thermostat.

A C-Wire, or “common wire,” provides consistent voltage to your smart thermostat, ensuring proper function and reducing issues like the blinking green light.

There are several methods to add a C-Wire to your setup:

  1. Connect a C-Wire directly from your system's control board to the thermostat.
  2. Use the Nest Power Connector, which supplies continuous voltage without needing hardwiring during installation.
  3. Use a Common Maker—an external device that generates continuous power for your thermostat.
  4. Use a C-Wire adapter – this offers another alternative, providing uninterrupted power to your Nest and is DIY friendly.
  5. Reuse the G (fan) wire as a makeshift C-Wire, ensuring a steady power source for your smart thermostat.

For more information on how to do this, check out my other Nest troubleshooting article here.

10. Hire a Nest Pro

When facing uncertainty or lacking confidence in fixing the issue yourself, reaching out to a local Nest Pro is a sensible choice.

These experts have the know-how and abilities to pinpoint and repair any thermostat or HVAC system issues.

Additionally, they are equipped to manage intricate tasks, like connecting a C wire or a Nest Power Connector, if necessary.

Nest Battery

11. Hardware Issues requiring a replacement device

At times, despite following all suggested steps, the blinking green light persists, indicating a hardware problem with your Nest Thermostat.

In such cases, the device must be replaced.

Before coming to this conclusion, ensure that all previous troubleshooting methods are exhausted.

If your Nest Thermostat falls under warranty, reach out to customer support for assistance.

They can guide you through any additional troubleshooting tips, and if necessary, provide a replacement.

Remember, it's essential to register your device and maintain records of your warranty information for a smooth replacement process.

How long should the flashing green light on a Nest Thermostat last?

The flashing green light on a Nest Thermostat should generally last no longer than a minute or two, indicating that the device is booting up and will soon be ready for use.

However, if the light continues to blink green for over 15 minutes and the thermostat remains unresponsive, this may signal an underlying issue that needs to be addressed.


I hope these 11 steps help you get your Nest Thermostat back up and running and fix the annoying flashing green light.

Let us know what worked for you in the comments below.


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