Whether that’s a blank screen, Wi-Fi issues, or the HVAC equipment acting strange, there’s always something you can do to fix a Nest thermostat that’s not working.
So instead of calling in the cavalry right away, you can try restarting the device for a quick fix.
But that might not be enough, so keep reading for a detailed troubleshooting guide.
Common Problems with Nest Thermostats
For the majority of cases, a Nest thermostat, regardless of the model, may run into the following issues:
- Nest thermostat won't turn on
- The thermostat is constantly running into “No Power” alerts or facing intermittent power issues.
- HVAC equipment failure or erratic behavior
- Problems with the Wi-Fi network and connection with the Nest and Google Home apps
- Issues with Home/Away assist and Eco Temperature features not performing as expected
If this seems like a lot to take in, don't worry. In this article, I'll cover the basics and quick fixes along with links to the more detailed troubleshooting guides.
At SmartHomePerfected we always advise readers not to undertake any work they are not competent in performing and if in any doubt, it is best to seek the assistance of a professional.
Issue 1. Troubleshoot a Blank Screen or Dead Thermostat
If your Nest thermostat doesn't turn on when you rotate the ring or press the button, it may be stuck or losing power.
In that case, check the app for any important alerts regarding your thermostat or note down the color of the light that's blinking.
If your thermostat is blinking red or green, the device might be running out of batteries or running into network issues. So check out this article to troubleshoot these blinking lights and a blank screen.
Issue 2. Troubleshoot “No power” Alerts on Your Nest Thermostat
In other cases, the thermostat might be powered on and responding to your touches, but it might not control the HVAC equipment. Instead, it might be putting out an error code or alert message.
Typically, the alerts and messages you might come across are:
- “No Power” or “No System Power” alert
- M20 or E298 Error codes
- Other error codes under the “E” label
- A “Low Battery” or “Very Low Battery” notification
- The thermostat disconnects from the Wi-Fi due to power-saving mode.
There can be several reasons why you would get these types of errors. The most probable are:
- Your thermostat is running low on batteries
- The thermostat wires are incorrect or coming loose
- Your thermostat requires a C wire but can’t detect one
- Your Nest power connector is disconnected or powered down
- The furnace control board or HVAC system is switched off at a breaker, fuse, or safety switch
- The rest of your HVAC system might be malfunctioning
So let’s start troubleshooting this type of error.
Step 1. Replace or Recharge the Batteries
First, make sure you have the Nest thermostat fully charged.
If you have a Nest thermostat 2020 model, you can easily replace the batteries with a fresh set of alkaline AAAs.
For the Nest thermostat E and learning models, you’ll have to charge the internal batteries using a Mini or Micro-USB cable. Let it charge overnight or for a solid couple of hours.
Step 2. Reset Any Circuit Breakers Or Safety Switches
After that, it’s a good idea to see if your thermostat and HVAC system is getting enough power. If your HVAC system is powered down:
- Check the circuit breakers, fuses, or any safety switches to make sure there’s enough power coming in.
- If any breakers or switchgear have tripped, try resetting them.
- Also, if your furnace is switched off, make sure the furnace door is properly closed
- Check the safety disconnects in your heating and cooling equipment. Make sure they aren’t damaged or loose.
Step 3. Check the Sensed Equipment on the Thermostat
Using the Equipment menu on your thermostat’s technical info panel, you can get a glimpse of the thermostat wires that are detected by the device.
This helps you figure out if the thermostat’s configuration matches the exact physical wiring setup in your home, helping you fast-track wiring issues without having to rely on a multimeter.
You can check the wiring information via mobile apps or the thermostat itself. Here’s how:
Check Equipment Information Via the Google Home App
- Open up the app
- (If you have multiple homes) pick the home you’ve set up the thermostat
- Head over to the “Devices” tab
- Select your thermostat
- On the thermostat control screen, tap on “Settings” and head over to “Device Information”
- Then, select the option titled “Equipment.”
On the Nest App:
- Open the app and select your thermostat
- After that head over to settings and tap on “Technical Info”
- Then, select “Equipment.”
On the Thermostat
- Press the ring button to wake up the thermostat
- Then open the quick view menu and head over to “Settings”
- Scroll down to “Technical Info” and select the “Equipment” tab.
Fix Any Undetected or Mismatched Wires
- After you open up the “Sensed Equipment menu” make sure to note down the wires that are detected by the thermostat.
- Wires that are detected will show up in blue, and ones that are detected but unconfigured will show up in orange.
- Meanwhile, wires that aren’t detected will be grayed out.
- If everything is grayed out, the HVAC system might be powered down. Make sure the system is switched on and open this menu, again.
- Then, note down the detected wires or take a photo of the thermostat’s wiring configuration.
- After that, remove the thermostat from the wall mount and check the actual wiring configuration in the thermostat’s wall mount.
- If you find any wire that doesn’t match up, make sure the wires are properly inserted into the connectors. However, don’t forget to turn off the power to the thermostat.
- Also, make sure the connector tabs are securely held down, if not, remove the wire and reinsert them, making sure the connector presses down firmly.
- If any wires are damaged or poorly stripped, strip them so they are straight and there’s a fair amount of copper exposed (around ⅓” to ½” should do the trick).
- Then, take a photo of the actual thermostat wiring configuration on your wall
- After that, reinsert the thermostat to the wall mount. Make sure you hear the device click into place
- Turn the power back on to the thermostat and your HVAC equipment
- Finally, head back over to the sensed equipment setting and check if the detected wires match the photo of the actual wiring diagram.
- If the thermostat isn’t picking up the connected wires, you might have to try factory resetting and reconfiguring your thermostat wires.
This above guide is also handy if you’re running into error messages declaring “Undetected,” “or “Unconfigured” thermostat wires.
Step 4. Install A C-Wire to Your Nest Thermostat
More often than not, a thermostat runs into power issues because it lacks a C-wire.
So if you face power issues with your Nest thermostat on the regular, I highly recommend setting up a C-wire for more power stability.
To learn everything about setting up a C-wire, make sure to check out this article.
If you run into any wiring issues or you need professional help installing a C-wire, don’t hesitate to reach out to a professional.
Issue 3. Fix Issues Where Your HVAC Equipment is Not Responding
Sometimes, your thermostat might be operating smoothly but your heating and cooling systems might not turn on when they should.
Troubleshooting an HVAC system is best left to the professionals. That being said, you can troubleshoot the issue at the thermostat itself and fix the most common problems.
Common problems with the HVAC system include:
- Weird noises in the heating and cooling equipment. These can be odd clicks, thumping, or chattering that’s too frequent and louder than usual
- The heating and cooling equipment is always turned on and never turn off
- The HVAC equipment turns on and off in a very short period of time (within minutes or even seconds)
- Your thermostat shows a “Delayed” or “Starts In” message when you adjust the temperature
- The blower fan never turns off
- An error code pops up in your Nest thermostat
- Heating equipment turns on when it’s supposed to cool and vice versa
- The thermostat switches to Eco temperatures when you’re at home
- The thermostat takes a long time (usually more than a couple of hours) to reach the desired temperature setpoint.
Step 1. Diagnosing the Issue: Checking Your Energy History
The first thing you should do, when diagnosing faulty HVAC equipment, is to check the energy history on your Nest thermostat.
Energy history will help you pinpoint any short cycling issues or any situations where the HVAC system was behaving erratically.
You can check energy history via Google Home, the Nest app or the thermostat display itself. Although I recommend going through the app since it’s more convenient.
Check Energy History Via the Google Home App
- Open up the app and select your thermostat
- Tap on “Energy dashboard”
- Select the time period you want to check, this can be a specific day, week, or month.
Check Energy History Via the Nest App
- Open the app and navigate to your thermostat’s home screen
- Then, tap on “History”
- A simplified view of the thermostat’s energy history (called the 10-day summary) will show up.
Via the Thermostat
- Wake up the thermostat and open the quick-view menu
- For Nest thermostat E: head over to “Settings” → “History”
- For the other models: simply select the “History” option in the quick-view menu
Step 2. Perform Maintenance on Your HVAC System
When your heating and cooling equipment starts acting funny, it might be an indicator of long overdue system maintenance.
If you haven’t replaced the filters, checked the equipment, or cleaned the vents in a long time, now would be a good time to do so.
So contact your local HVAC company and get them to perform maintenance on your HVAC system. In the process, they might also be able to pinpoint any issues within the equipment.
Step 3. Check for Compatibility With Your HVAC System
Nest thermostats are very flexible and can adapt to work with most 24V systems but there's a catch; certain system types and specific models from select manufacturers won't mesh well, especially since the majority of systems require a C-wire for more stable power management.
Essentially, the following types of systems are incompatible with Nest thermostats:
- Proprietary systems
- Millivolt systems
- High voltage/line voltage systems
- Systems with solid fuels
For more information on compatibility, make sure to go through Google’s compatibility checker.
Step 4. Other Solutions
Beyond, resolving compatibility issues and fixing your HVAC equipment, you can also consider options such as:
- Checking the thermostat wiring for any hardware defects
- Installing a C-wire to your thermostat
- Setting up a Nest Power Connector as a means of adding a virtual C-wire
- Factory restarting the thermostat and reconfiguring the equipment to match your current setup
Issue 4. Diagnose and Fix Connection Issues with the Wi-Fi and mobile apps
When it comes to network issues, the most common troubleshooting process turns into:
- Identifying the reason for the connection failure
- Fixing issues with the Wi-Fi signal strength
- Making sure router settings are correct
- Restarting or reconnecting the thermostat with the Wi-Fi network.
Depending on your situation, troubleshooting network errors can range from a simple router restart to a more tedious factory reset with your Nest thermostat.
Whatever the case, I highly recommend checking out this article, where I've created a more comprehensive guide that covers connectivity issues for Nest thermostats.
Issue 5. Issues With Home/Away Assist and Eco Temperatures
The Nest thermostat has the ability to automate your home's temperature settings based on whether you are home or away using the Home/Away Assist and Eco Temperatures.
These features use motion sensors and geofencing, which detect when you leave and return to your home. They will adjust the temperature when you’re leaving, so it can save energy and bring it back up to comfortable levels when you return.
In certain instances, these features can be counterproductive, automatically adjusting the temperature even when you’re at home.
So, disabling Home/Away Assist can help you take more control of the thermostat, at least until you figure out why these automated functions are not performing as expected.
Troubleshoot Why Home/Away Assist Is Inaccurate
Since Home/Away Assist and Eco temps are not particularly related to hardware, adjusting the software settings and making sure your Nest thermostat and smart devices are performing smoothly can help you fix any related issues.
So make sure to follow these troubleshooting steps:
- Enable Location On Your Smart Device: With geofencing enabled, your thermostat detects your presence using the location of your smartphone or smart device. Make sure this setting is enabled and functioning.
- Make Sure Your Smart Devices Have Access to The Internet: If you’ve set up your smartphone with your Nest thermostat, you want to make sure that it can always connect to the Internet, either via Wi-Fi or cellular data. This helps improve location accuracy and also helps the thermostat constantly check if you’re home or away.
- Avoid Sharing Accounts: Don’t share your account credentials, for the Nest app or Google Home, with guests or family members since it can cause incorrect readings. You can instead grant access to others via Family Accounts.
- Avoid Changing Temperatures Manually: Setting up temperature holds or adjusting to Eco temps manually, can sometimes override your home/away assist settings, especially when auto-scheduling is disabled and eco temperatures are set to “Off.” So make sure to cancel manual changes whenever necessary.
Troubleshooting a Nest thermostat isn’t very complicated once you understand the issue and how the thermostat operates. Whether that’s power issues, network errors, or settings changes, identifying the exact cause and taking steps to resolve should help.
If not, I recommend reaching out to a professional engineer to carry out some more advanced troubleshooting.