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Nest Thermostat Cycling On and Off: 6 Reasons and Fixes

Nest Thermostat Cycling On And Off

According to The New York Times, the Google Nest Thermostat sweeps the competition away and takes the spot of the best smart thermostat on the market.

However, that doesn’t mean you won’t experience a few challenges using this gadget.

For example, you may notice that sometimes your Nest Thermostat starts cycling on and off.

The common causes of Nest Thermostat cycling on and off include connecting it to your old wiring, using worn-out batteries, a faulty fuse, or software issues. To fix these problems, you need to replace your batteries, redo the wiring, change the fuse and update the Nest Thermostat software.

The rest of this article will explain the reasons your Nest Thermostat cycles on and off and how to fix them.

Read on to benefit from these and learn more information on the following:

  • How to change the Nest Thermostat batteries
  • How to update the Nest Thermostat software
  • How to troubleshoot defective HVAC equipment

1. Old/Wrong Wiring System

If your Nest Thermostat keeps cycling on and off, it’s best to check your wiring system.

Sometimes loose connections from old wires in your house hinder the smooth flow of electric current to your device.

Your Nest Thermostat draws its power from your home’s main supply line or the HVAC equipment through a common wire (C-Wire), which makes it possible for the HVAC equipment to charge the thermostat’s batteries.

Although the design of the Nest thermostat prevents it from using too much power, bad wiring may increase the amount of current necessary for the battery to fully charge.

As a result, your thermostat may not recharge to the optimum.

Consequently, the thermostat’s batteries may drain quickly, forcing you to recharge it within a short time.

To fix this problem, you have to replace or redo the wiring that connects your Nest thermostat to the HVAC equipment. You may also need to replace the C-Wire. 

Fitting a common wire and adapter on your Nest thermostat will keep the battery level up for several months.

Here is a detailed video explaining how you can connect a common wire to the Nest Thermostat:

You can also use the USB cable that comes with the Nest to charge the batteries directly.

However, this means more work since you’ll need to recharge the Nest thermostat every time it drains.

Note: Redoing the wiring is a complex process that may require help from a professional.

Also, ensure the mains are off when reinstalling your home’s wiring system – live electrical wires may cause electrocution!

You might also like: Why does my Nest Thermostat say “Delayed for two hours”?

2. The Batteries Are Old/Worn Out

The Nest Thermostat comes with a built-in battery that powers its interface, letting it connect to the Internet and interact with your HVAC equipment.

The battery also acts as a backup option in the event of a power cut.

However, problems arise when the battery wears out and can’t hold sufficient power anymore. It may drain fast, shutting the thermostat down sooner than expected.

Interestingly, worn-out batteries charge just as fast as they drain.

Once the Nest goes off, the battery initiates charging again, and within a short time, it is complete.

If this happens several times, it gives the impression that the Nest Thermostat is cycling on and off.

To solve this problem, you should replace the old batteries with new compatible ones.

To replace the batteries, follow these steps:

  1. You need to plug out the Nest Thermostat from the wall.
  2. Identify the location of the old batteries.
  3. Remove the old batteries from their socket.
  4. Replace them with 2 new 1.5V AAA alkaline batteries.
  5. Return the Nest thermostat to its position on the wall.

If you need quality batteries, I recommend these Amazon Basics AAA Batteries from They are high-performance batteries with a 10-year shelf life and offer a 1-year warranty.

3. Look Out for a Faulty/Damaged Fuse

A faulty fuse is one of the issues you’d least expect to interfere with your Nest Thermostat.

However, it happens, and chances are it’s the reason your Thermostat is cycling on and off.

If the fuse is blown, the thermostat won’t function at all.

But if it fits loosely in the fuse box, you will experience intermittent power losses that cause the thermostat to keep cycling on and off.

The only way to fix this problem is by replacing the fuse.

Simply identify which fuse is loose or blown and replace it with a new one.

4. Direct Heat Source/Sunlight May Affect the Thermostat

If you position your Nest Thermostat directly to sunlight or a heat source, it may start behaving abnormally.

The heat from the sun will give the thermostat a false impression that it’s overheating, which forces it to shut down as it tries to protect its components.

You will realize this when the temperature readings on your Nest are inconsistent with other Thermostats in different rooms.

To fix this problem, relocate your Nest Thermostat away from direct sunlight.

Also, check the wiring and base of the Nest to make sure they are not heating.

5. Defective HVAC System

If your HVAC system is defective, you may notice some strange behavior from your Nest.

For instance, it may turn on and off constantly or sometimes turn on but fail to turn off.

In most cases, this happens because the Nest Thermostat isn’t drawing enough power from the HVAC system.

You can diagnose the problem to determine if the system needs maintenance or if the problem originates from the thermostat itself.

You’ll need a different Nest Thermostat to perform the diagnosis.

Follow these steps to determine the cause of the problem:

  1. Disconnect your system from the main power line.
  2. Remove your Nest Thermostat from the wall and disconnect it from the HVAC equipment.
  3. Install the other Nest Thermostat on the wall and connect it with the HVAC equipment.
  4. Power the system back on

If the Nest Thermostat keeps cycling on and off after replacing the Nest Thermostat, chances are your HVAC system is faulty.

To fix this problem, you’ll need to call a HVAC technician to run more tests on the system and identify the best solution.

However, if the system works fine once you replace the Nest Thermostat, you might want to check your wiring.

Reading recommendation: Do Smart Thermostats Work With Heat Pumps? 9 Facts Revealed

6. Bugs and Software Issues

Software issues and bugs are not new to Nest Thermostats.

However, different bugs have different effects on the device.

A software bug can make the Nest Thermostat cycle on and off. It affects the charging of the battery and also makes it drain faster than it should.

This problem may occur after a faulty or incomplete software update.

Although Google will often fix this problem whenever it occurs, that may not happen 100% of the time.

However, a manual update may come in handy to keep the thermostat running smoothly.

To update your Nest Thermostat software, follow these steps:

  1. Press the Nest ring on the thermostat.
  2. Navigate to settings.
  3. Click on the software.
  4. Click the update tab.

Note that Google issues updates in batches.

Therefore, the Nest Thermostat software update may not be the same for all Nest Thermostats.

Check out: Second Nest Thermostat Won’t Connect to App: 5 Quick Fixes

Final Thoughts

Nest Thermostats cycle on and off due to faulty wiring, loose fuses, faulty HVAC systems, or software bugs.

Also, placing your thermostat close to a direct heat source interferes with its operation.

By following the tips in this article, you should fix the problem.

However, I advise that you consult a qualified technician or call the Nest Thermostat support center if the problem persists or involves handling live electrical wires.

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