10 Reasons Why Google Nest Thermostat Is Not Turning On Heat

Smart products like the Google Nest thermostats are becoming increasingly common. But since it is an electronic device, it becomes problematic over time. So, is your Nest thermostat not turning on the heat? Let’s find out why. 

There are several reasons why a Google Nest thermostat may not be turning on the heat, including issues with the wiring, power supply, or temperature settings. It is recommended to check the wiring connections, ensure the thermostat receives power, and adjust the temperature settings if necessary.

Each problem has different solutions, but one temporary solution that works for all is resetting or restarting the thermostat. If you are finding solutions for your problematic thermostat, this article has everything you need to know.

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What is a Google Nest thermostat, and how does it work?

The Google Nest thermostats are made by Nest Labs and acquired by Google. 

It is an AI-enabled thermostat that can optimize the temperature of the surrounding environment by using only a limited amount of energy.

Being a smart thermostat, it will learn your preferences over time and adjust automatically to meet your needs. 

This further saves you time and energy in the long run.

The Nest thermostat works with the Google Home and Nest App on iOS and Android phones. 

The optional Nest Pro installation services do most of the hard work if you are away from the house. 

It can determine the best place for installing the thermostat and teach you how to use the device and connect it to the other smart house devices.

After the installation, the thermostat learns about your preferences, adopt them, and adjust them according to your need. 

The Google Nest thermostat contains several sensors that can detect the current temperature, humidity of the surrounding, the presence of people in the room, and the amount of sunlight it receives. 

These data help the thermostat determine the best way to maintain a comfortable environment in the room by utilizing a small amount of energy. 

At times, however, you will notice that the Nest thermostat is not turning on the heat. Several reasons could be responsible for such a situation, for example:

  • Power supply issues
  • Outdated software
  • Weak network signals 
  • Battery problems
  • Heat link problems 
  • Incompatibilities 
  • Low maintenance 
  • Incorrect or loose wire connections 
  • Dirty sensors and air filters

These problems are relatively easy to fix, and that is what this article is about. 

Also read: 10 Reasons Why Your Google Nest Thermostat Is Not Working

So, let’s get to the bottom of these problems in detail and the ways to solve them. 

1. Power supply issues 

Insufficient power supply issues are one of the common reasons behind the Nest thermostat not turning on the heat. 

It happens when you have a blown-up fuse. 

If there has been a sudden power surge, the fuse inside the HVAC system can blow up, and the system does not turn on the heat. 

So, you have to replace them with a professional.

The Nest thermostats also have fuses inside. 

If that too gets damaged, you must replace them for enough heat.

Unlike the other thermostats, you cannot open this model on your own.

Call a Nest professional to fix the issues.

While buying a new fuse, use the same model and voltage as the old one.

Incompatible fuses will not let your Nest thermostat work.

2. Software updates

Since the thermostat runs with apps and software, it must stay updated. 

With outdated versions, the thermostat will malfunction and won’t turn on the heat.

So, update the software and start the thermostat again.

To update your Nest thermostat:

  1. Go to the thermostat and click on SETTINGS.
  2. Then select SOFTWARE. 
  3. You will see the version you have and also get an UPDATE option if there is any available.
  4. Click on the UPDATE. 
  5. Your thermostat will check for updated versions and download the latest software update.
  6. Once you finish this, you are all good to go.

You must have the ideal application to do it from your mobile app. After that:

  1. Go to the mobile app. 
  2. Choose the Nest thermostat.
  3. Select the SETTINGS NEST icon. 
  4. Click on VERSION or SOFTWARE and check for updates. 
  5. If there is an update, an UPDATE option will pop up. 
  6. Click on it and update the software. 

3. Network issues

The digital Nest thermostats work by Wi-Fi connection. 

Without this, it won’t function and provide you with the best features. 

If the connection is weak, the thermostat may not be able to provide you with enough heat or cold air. 

So ensure that you have a strong Wi-Fi connection. 

Also, remove the obstructions and interferences. 

Only add a few devices with the same router. 

Keep the thermostat within the range of a Wi-Fi connection. 

Most Nest thermostats will be compatible with the 2.4 GHz Wi-Fi band frequency. 

Also, captive portals and enterprise networks don’t support the Nest thermostats. 

Home Wi-Fi networks are considered the best ones for Nest thermostats.

4. Battery issues

Sometimes low or dead batteries lead to the thermostat malfunctioning, for which it will not turn on the heat. 

Since the thermostat is digital, it will alert you about the low battery level. You should be ready to face the problem if you have ignored it. 

To prevent this, replace the batteries and restart your Nest thermostat to check the heating system. 

5. Heat link problem 

The Nest thermostats can cool the room without a problem, but it will need a Heat Link for the heat. 

Without a proper connection with the Heat Link, your thermostat cannot signal the heating system to turn on the heat.

So, to connect the Nest thermostat to the Heat Link:

  • Press the HEAT LINK button once on the 2nd and 3rd generation thermostats.
  • For older Nest thermostats, press the HEAT LINK button twice.

6. Incompatibility

The Nest thermostats and Nest thermostat E are primarily compatible with 85% of the HVAC systems. 

The Google Nest Learning Thermostat is compatible with 95% of HVAC systems. 

The Nest Learning thermostats are designed for most 24V and older systems. 

They work with all types, like natural gas, oil, and electricity.

So, you need a compatible thermostat model for your heating systems to turn on the heat. 

To be sure about the compatibility, use the Compatibility Checker Tool. 

It has all the instructions to check whether the heating system is compatible with your thermostat. 

You may have to replace the thermostat if you have an incompatible one.

7. Low maintenance

When you don’t maintain your thermostat, it can malfunction and stop turning on the heat or cool, whatever you need. 

If your thermostat turns orange when you turn on the heat, but your system does not turn it on, it indicates the need for a maintenance task.

Please turn off your thermostat and the HVAC system at the breaker, wait for some minutes, and turn it on again. 

This should fix the problem. 

But if the problem returns after some minutes or hours, call a Nest or HVAC professional for repair and maintenance. 

8. Wiring issues 

When the heat does not turn on in your Google Nest thermostat, the reason could be incorrect or loose wire connections. 

Here, the wires connected to the heating system might be damaged, wrongly wired, or have loose connections.

You will understand the faulty wires when you open the thermostat’s cover plate. 

You must adjust them accordingly for smooth functioning. 

The Nest thermostats are sensitive to wiring. 

So, each wire needs to be connected properly and tightly. 

Any little kink can create issues in the heating system.

Be particularly mindful of the W-wire and the Rh-wire. 

The W wire in the thermostat is connected to the heating system and controls the heat. 

The Rh wire is the switch of the heating system that starts the heat. 

If these wires are loose, wrongly connected, or the terminals get mixed up with other wires, your thermostat will not turn on the heat.

To fix the incorrect or loose wire connections in the Nest thermostat:

  1. Turn off the power of the thermostat at the breaker.
  2. Remove the display and check whether all the connectors have their respective wires. 
  3. Check especially for the W and Rh wires. The W-wire should be in the W terminal, and the Rh wire in the R terminal. 
  4. Check the other wires as well, especially the C-wire. It gives power to the Wi-Fi thermostat for constant operation day and night. 
  5. If there are any loose wires, re-strap, straighten, and reconnect the wires tightly. 
  6. Recheck everything and cover the display. Turn on the thermostat and check the heat.

If you want to rewire your thermostat anew:

  1. Turn off the breaker of your thermostat.
  2. Open the thermostat cover plate and find the wires. 
  3. Consider the original setup of the wires and rename them. 
  4. Click a picture of the Nest wiring setup for reference. 
  5. Use Google’s free Nest thermostat compatibility checker and enter the wires. 
  6. Remove the display screen.
  7. Connect, disconnect, and reconnect the wires based on the picture and compatibility diagram.

After you finish rewiring, put up the display screen, and turn back the breaker. 

Wait until the thermostat boots up. After the reboot, it should be fixed.

Remember that the wires in the Nest thermostats are slightly different from the others as they use low-voltage wires.

Call a professional once for proper guidance.

Also read: Google Nest Thermostat Not Detecting Wires? (8 Causes+Fix)

9. Dirty or obstructed sensors

The thermostat contains sensors that detect the surrounding temperature and produce the readings. 

The sensor fails to detect the temperature if it becomes dirty or obstructed. 

So, the heat cannot turn on with no readings.

If the sensor is dirty, open the thermostat cover and clean the sensor with a cloth or brush. 

But if the sensor gets damaged, you must replace it with a new one.

Call a professional to replace the sensor. 

Make sure you use the compatible sensor in the Nest thermostat. 

Also read: 10 Ways To Fix Temperature Differences Between Rooms

10. Dirty flame sensor

Here we are talking about the furnace’s flame sensor. 

If the sensor is dirty, it cannot detect the flame after you turn on the furnace. 

As a result, the heat will not turn on.

To fix the flame sensor:

  1. Shut off the power to the thermostat and the furnace. 
  2. Turn off the gas valve and check for the sensor rod in the burner assembly.
  3. Remove the sensor and closely examine it.
  4. Check for cracks, missing pieces, or damage. If there are any such things, you must replace the sensor with a new one. 
  5. For corrosion, use sandpaper, steelwork, or wire brushes to clean the carbon buildup. 
  6. Now, wipe it with a clean cloth or paper towel.
  7. Screw the sensor back in the furnace and turn on the heat.

What else can I do to troubleshoot the Nest thermostat that is not turning on the heat?

If you cannot fix the Nest thermostat that is not turning on the heat, try 3 things:

  1. Restart your thermostat. 
  2. Power cycle or reset your thermostat. 
  3. Reinstall the old thermostat if you have any. 

Restart your thermostat

This solution can solve most of the problems. 

You can keep the Restart method as the first resort or the last. 

I keep it as both, based on my preference.

Restarting the Nest thermostat will refresh your system and remove all its errors. 

For restarting the thermostat:

  1. Find a thermostat ring, press it, and go to the QUICK VIEW menu.
  2. Press the QUICK VIEW menu, 
  3. Find the THERMOSTAT RING on your Nest device.
  4. Go to the SETTINGS.
  5. Go to RESET, and press SELECT.

If the screen freezes and you cannot return to the QUICK VIEW menu, press the ring and hold it for 10 seconds. 

Then do a hard reset. 

Press the ring again and return to the Nest thermostat running again.

Reset or Power cycle your thermostat

Resetting will remove all the errors, too, like the Restart. 

But the factory reset will also remove all the enabled features in the thermostat and make it a newly manufactured device.

Try a soft reset first:

  1. Push the Nest thermostat ring for 10 seconds. 
  2. Wait until you see the ring stops lighting up. 
  3. Wait for 10 seconds again.
  4. Push the Nest thermostat ring for 10 seconds again to power it up.

If this doesn’t work, try to reset the Nest thermostat again with the following steps:

  1. Open the QUICK VIEW menu and press the Nest ring.
  2. Select the SETTINGS when the ring turns. 
  3. Click on the ring, and select RESET. 
  4. Choose the ideal reset function, AWAY, SCHEDULE, NETWORK, or ALL SETTINGS. 
  5. For RESET FUNCTION activation, click on the ring. 

Another option is to try to Power Cycle the Nest thermostat:

  1. Go to the SETTINGS.
  2. Select RESTART if you have the Nest thermostat mirror version. 
  3. Or select RESET, and then choose RESTART if you have a Nest Thermostat Learning or E version.

Reinstall the old thermostat

The last step is to reinstall the old thermostat. 

It will give you a temporary fix and let you know whether you have any wiring issues.

If the heat does not turn on even after reinstalling the old thermostat, you have faulty wires which need to be fixed by an expert.

To reinstall the old thermostat:

  1. Turn off the breaker powering the thermostat. 
  2. Remove the Nest thermostat unit.
  3. Label the wires with masking tape or marker.
  4. Remove the base plate. 

The crucial step here is to remove the wires and reconnect them. 

It is where you must be careful about connecting the wires to the correct terminals. 

If this doesn’t solve the problem, hire a professional.

When should I call a professional?

It is the last solution after the last resort; you do not have to do anything here. 

Contact the professional for help. 

Sometimes, the thermostat stops turning on the heat if you have hardware issues. 

So, it will need an expert’s attention. 

Calling a professional if your device is under warranty will save you enough money and time. 

Experts will fix the problem correctly with less time and effort.

Explain the problem to the professionals and inform the troubleshooting steps you have attempted. 

They will easily understand the problem and fix it quickly.

However, some moments confirm that professional help is a must:

  • Electrical issues like fire hazards and short circuits are some areas that need an expert’s help. You would want to limit the HVAC usage until the professional arrives to reduce further damages. 
  • You must call an expert when an HVAC is going haywire due to fire hazards.
  • If the thermostat has died, call a professional, especially if you still have the warranty period. 

Final thoughts

If you have reached the end of the article, you have learned all the possible reasons behind a Nest thermostat not turning on the heat. 

Start checking the system and ruling out all the problems one by one. If nothing works, try to restart, reset, or power cycle the Nest thermostat or reinstall the old device.

If you still cannot fix the problem, call a Nest professional and an HVAC too, if the problem is due to the HVAC unit of your house.

Can I manually override the Nest’s scheduling?

You can do it, but the best way is from the Nest app. For a manual, switch the Nest mode from AUTO to MANUAL. Search for different settings and customize your schedule.

What is the ideal temperature to set in the Nest thermostat?

It is best to stick to ECO mode as it keeps between 40-70°F for energy savings. You can choose temperatures between 70-90°F for cooling the Nest. 60-73°F is the best.

Reference: Nest Thermostat Wikipedia

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Arthur Smith

Howdy! I am Arthur Smith, an electrical engineer who is extremely passionate about electronics. I have lived in different parts of the US and currently reside in Wisconsin. I am one of those rare children who knew what he wanted to study and do in life right from the start. I was a curious child who wanted to know how switches work and how the AC works, and I would always observe my dad whenever he would handle the wires and fix things around the house. I currently work as an electrical engineer at a reputed company and write for this blog. And I read loads of books or play video games in my free time.

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