10 Common Problems with Nest Thermostat

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Common problems with Nest thermostat

Google’s Nest Thermostat is one of the most popular and best-selling smart thermostats in the United States at the moment. Thanks to the wide range of benefits it comes with such as being compatible with most modern 24V heating and cooling systems. Plus, it automatically learns your preferred temperature preferences, creating a customized energy-saving plan for your home. 

However, despite being one of the best smart thermostats in the market, there are various Nest Thermostat problems you’re likely to encounter, causing your device to malfunction. Luckily, some of these issues are relatively easy to fix, even without having to contact a professional. Besides, this guide will show you how to troubleshoot common problems with the Nest thermostat and some easy DIY fixes!

Troubleshooting Common Nest Thermostat Problems 

1. Nest Thermostat not charging

A Nest thermostat either charges its batteries through the C-wire or by power stealing when the HVAC system is running. Unfortunately, if the device isn’t charging itself through any of these methods, you’ll frequently encounter low battery issues. This can further lead to more problems like the thermostat not turning on, Wi-Fi connectivity issues, and so on. 

That said, if your Nest Thermostat isn’t charging, the first thing you need to do is to check whether the C-wire is properly connected. To accomplish that, remove the thermostat from the mounting bracket and look for a wire attached to the terminal labeled ‘C’. Make sure that the wire is connected properly to the terminal and return your Nest to the wall. 

A loose C-wire can hinder the thermostat battery from charging. Hopefully, tightening it will solve the issue of your Nest thermostat not charging. However, if the C-wire is properly attached or your system doesn’t have a C-Wire, look for other solutions. This may include;

  • Connect G-wire to the C-wire terminal to continuously charge the thermostat. This approach involves removing the G-wire from the G-terminal and connecting it to your HVAC system’s C-wire terminal.
  • Use a 24V C-wire transformer. If your HVAC system isn’t supplying adequate power to your Nest thermostat, connect the 2 wires of a 24V C-wire transformer to your device’s Rh and Rc terminals. 
  • Charge your Nest thermostat with a USB cable. This technique is recommended when your HVAC system has been off for a long time. It’s relatively easy since you only need to remove your device from the wall and plug a mini-USB or micro-USB cable into the port on the back. Next, connect the USB to a regular wall charger, and plug it into a power outlet. Let your Nest device charge for about 2 hours.

2. No C wire for Nest Thermostat

Nest smart thermostats require a C-Wire (common wire) to constantly supply power to the device. If the device has no C wire, it might not get enough power. However, if your thermostat doesn’t have charging issues, this will not be a problem. The batteries will supply constant power to the thermostat.

On the contrary, if your Nest Thermostat batteries frequently run low, consider installing an add-a-wire adapter to your temperature control system. As the name suggests, this involves adding a wire to your existing heating and cooling system, which is a cheap and easy way to fix the C-wire problem. Alternatively, consider replacing your Nest thermostat with a smart thermostat that doesn’t require a C-wire like Ecobee.

3. Flashing green light on Nest Thermostat

A blinking green simply shows that your Nest Thermostat is getting a software update from Google. This happens from time to time and only takes a few minutes to complete. However, if the blinking green light lasts longer than usual, this shows that device’s control board is non-responsive. To fix that problem, disconnect your Nest device from the base, line up its pin connector, put the thermostat back on the base until you hear a clicking sound. and restart the system.

Once you’ve done that, the reconnecting display will come on. If it doesn’t, press the device for a few seconds to restart it. Afterward, the software update might run again, but the blinking green light will be gone.

4. Nest Thermostat Red/ orange light

A blinking red/ orange light in your Nest Thermostat usually shows that the battery is low. This can be accompanied by other signals like a home symbol/ low battery message on the display, or blank screen. In addition, this can prevent the thermostat from staying connected to the Wi-Fi or make the HVAC system stop working until you resolve the issue.

To fix this problem, charge your Nest device by connecting it to a C-wire transformer or wall charger USB cable. Alternatively, you can connect your device to the HVAC system G-wire if your system doesn’t have a C-wire. 

5. Nest Thermostat yellow light

This Nest thermostat problem is usually experienced by European thermostat models. To be precise, a flashing yellow light shows that your Nest device cannot connect to a Heat Link. Heat Link is a device that connects European Nest Thermostat models to heating systems. 

If you encounter this problem on your Nest device, click the button on your Heat Link to check the status. And check the thermostat display or Nest app for a message or error code. Alternatively, press the Heat Link button twice to manually deactivate or activate the heating system.

In most cases, problems between Nest and Heat Link will resolve on their own. However, if you get an error code in your thermostat display/ Nest app, contact Nest support or check it out on the Nest help codes list.

6. No power to Rh wire Nest Thermostat (E74 Error Code)

The nest thermostat displays an E74 error code on the screen when it can’t draw power. More importantly, it shows that there is no power to the device’s Rh wire. Hence preventing the heating system from turning on. Some common causes of this NEST thermostat problem include; a loose Rh/ Rc wire, tripped breaker, or a blown fuse in the air handling unit.

If you notice an E74 error code on your Nest thermostat display, check the source of the power issue first before you look for a solution. For instance, check if there is a blown fuse in their air handler’s fuse box or if there is a power outage. Also, check if the Rh/ Rc wires are properly connected and fix the thermostat wiring if it has any problem. In case of a tripped breaker, switch the corresponding breaker off and on, then check if your device will be powered. 

7. Nest Thermostat not connecting to Wifi

As already mentioned, one of the main issues that make your Nest Thermostat experience Wi-fi connectivity problems is low battery. However, this problem can also be caused by an issue with the Nest service or the lack of a C-wire in your system. 

If your Nest device cannot connect to the Wi-Fi network, you’ll receive error codes like M22 and M21 on the thermostat display. Interestingly, you can solve this problem by trying the following fixes; 

  • Restart the thermostat. To do that, go to the Settings on your display, then to Reset, and finally press Restart. 
  • Reset your Nest thermostat network settings. Go to Settings, then to Reset, and select Network. Although the real power of a smart device requires an internet connection, there are some Nest features that allow you to use the device without Wi-Fi. 
  • Restart the Wi-Fi Network. Unplug your Wi-Fi router for about 30 seconds, then plug it back in to restart your Wi-Fi network. 

More importantly, follow the solutions I mentioned above to fix the no C-wire and low-battery problems. Also, try moving your router closer to the thermostat to see if that will fix the Wi-Fi connectivity issue. 

8. Nest Thermostat showing the wrong Temperature

Various factors can make your Nest thermostat display a different temperature from the actual temperature in your home. But before we get there, you should note that the Nest thermostat display shows 2 temperature readings. The actual room temperature appears at the edge of the screen, while the large one in the center of the display is the set target temperature. 

With that in mind, let’s discuss why your Nest thermostat may be showing an inaccurate temperature from the actual indoor temperature. 

First, the thermostat can only monitor the temperature of its location. Yet various parts of your home have different temperatures. For instance, if you place your Nest thermostat near a heat source, it will certainly read a higher temperature than the actual room temperature. The same case applies when you install the thermostat in direct sunlight, near kitchens, and so on. To avoid these issues, determine the best place to put your Nest Thermostat in your home. 

Secondly, a wrong temperature reading on your Nest device may indicate that the device is catching up to a recent temperature. This is because the actuarial temperature tends to fluctuate outside the set temperature band for various reasons. For instance, the Nest thermostat has an inbuilt delay feature that prevents it from responding instantly to minor temperature changes to save energy. 

In addition to finding the best thermostat placement location, consider adding a Nest Temperature sensor to your heating and cooling system. This will help you get an accurate temperature reading, especially if your device is installed in a particularly cool/ hot area of your home or if you’ve got a large home.

9. Nest thermostat keeps Short cycling the HVAC system

Short cycling refers to when your Nest thermostat shuts off the AC or heating system before the room reaches the desired temperature. This can be quite frustrating since it prevents your home from being warmed or cooled to the preferred temperature. 

Various issues with your Nest thermostat can make your HVAC system exhibit this rapid on-&-off behavior. Most of these issues are accompanied by strange sounds like chattering, clicking, and thumping. 

Here are some of the Nest thermostat problems that can make your HVAC system short cycle; 

  • When the battery voltage of your Nest device drops too low. To prevent this from happening, add a C-wire to your Nest device to keep its battery charged. 
  • The Nest thermostat is sensitive to power interruptions. One of the best ways to solve this issue of the Nest device’s sensitivity to power interruptions is to install a 24V AC adapter. Besides, this will provide constant power to your device’s battery, keeping it fully charged. 

10. Nest Thermostat says delayed

Lastly, if your Nest device is displaying a delay message, it’s an indication that the system is underpowered. This usually occurs when you install your Nest smart thermostat without a C-wire. Therefore, you need to ensure that your thermostat connectors have a C-wire to constant charge your device and prevent this message from reappearing. Also, you can consider installing an add-a-wire accessory as mentioned earlier to fix the C-wire problem. 


Those are some of the most common problems with the Nest thermostat most users are likely to encounter with their devices. But as you’ve seen, most problems are easy to fix. You only need to identify the cause of the problem first, then find the perfect solution and your device will be working perfectly. However, if you’re having trouble trying to identify the issue with your device, consider hiring a reliable AC repair technician in your local area. 


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