Turning the Nest Thermostat on and off: reasons and solutions (2023)

If the temperature in your home isn't as comfortable as it should be, your Nest Thermostat may have started cycling on and off. So the question is, can you troubleshoot and fix the problem yourself?

If the Nest Thermostat keeps turning on and off, in most cases you can find the problem and fix it yourself. Problems like dead batteries and blown fuses are easy to fix. However, if the old wiring needs replacing or the thermostat has software issues, you will likely need to contact a qualified technician.

In this article, we will introduce an easy way to troubleshoot. We have identified 6 categories that may be related to activation/deactivation issues. Typically, you will find that only one of the categories is affected.

We'll discuss each category and give you tips on how to fix the problem. The categories are in no particular order, so you can start troubleshooting with any one of them.

Categories for Fixing the Nest Thermostat Cycling Issue

Problems that cause the thermostat to turn on and off are usually related to one of the following:

categoriesPossible problemsDIY solution?
wiringOld/wrong wiring Loose connectionsYou may need professional help. generally do it yourself
batteriesDepleted replaceable batteries Defective internal batteryReplace the thermostat do it yourself
FuseBlown fuse Dirty fuse contact pointsHouse made
thermostat placementNear other heat sources or in direct sunlightHouse made
SoftwareRequires bug updatesDIYers may need professional help
Other HVAC equipmentError on one or more devicesYou may need professional help.

Reason 1: Problems with the cabling

If the Nest Thermostat keeps turning on and off, the problem could be with the wiring.

A)Incompatible old wiring or incorrect wiring connectors

The problem

If the cycle problem started shortly after replacing the thermostat or any of the HVAC units, there's a good chance that the wiring was accidentally miswired during the replacement process, or that the thermostat is not compatible with the existing wiring. Hec wireit could also be connected to the wrong thermostat terminal. If the connections are made incorrectly, no power will flow to the thermostat's battery and if the battery dies, the thermostat may start cycling on and off.

the possible solution

To troubleshoot the problem, refer to the wiring diagrams and instructions that came with the thermostat or appliance and compare the thermostat and appliance connections. Remember to completely turn off the thermostat and HVAC system before starting any wiring work.

If you find cables connected incorrectly, swap and reconnect them correctly. To verify that you have corrected the problem, turn the HVAC system and thermostat back on. Wait about two hours to allow the battery to charge and check that the thermostat still cycles on and off. If not, you've solved the problem.

If the problem persists

If the problem persists then troubleshoot the other categories and if after all the troubleshooting the problem is still not resolved then you will need to contact your HVAC technician for assistance. The technician then tests, among other things, the compatibility of the new thermostat with the existing wiring in your home.

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B)loose connections

The problem

Loose connections in your HVAC system can prevent electricity from flowing properly to the thermostat. This can cause the battery to drain faster than it charges and the thermostat to turn on and off. Bad connections can also turn the thermostat off and on again.

the possible solution

To find loose connections, you can use the Technical Info Chart feature provided by your Nest Thermostat. Look for this feature option on your thermostat and open it. The diagram shows all loose connections in red.

Turn off the HVAC system, remove the thermostat cover from the wall base and locate the loose connections shown in the figure. Secure all wiring and reinsert the wire into the thermostat connector if necessary. To reinsert a cable correctly, press the button on the connector and push the cable in as far as it will go. The cable is installed correctly if the button on the connector stays in place when you release it.

Once you are sure that all connections, including the thermostat connections, are secure and properly aligned, place the display back into the base and turn on the system.

If the cycle stops in about two hours, done!

If the problem persists

However, if the power cycle continues, you should continue with your troubleshooting.

Reason 2 – Battery related issues

Battery-related issues are often the reason why the thermostat turns on and off.

A)Replaceable button cells

The problem

Some Nest Thermostats come with 2 AAA batteries for supplemental power when HVAC system power is insufficient. These batteries also serve as a backup option in case of a power outage. As they age and no longer have a high current load, the thermostat may turn on and off.

The solution

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Replace the 2 batteries with identical new ones and the problem can be solved.

To replace the batteries, you must turn off all power to the thermostat and then unplug the Nest Thermostat from the wall. Remove the used batteries from their sockets and replace them with 2 new 1.5V AAA alkaline batteries.

Return the Nest Thermostat to its position on the wall and turn it back on. If the batteries are the problem, the thermostat will stop working.

If the problem persists

If the problem persists, you must troubleshoot the other categories.

B)built-in battery

The problem

Many Nest thermostats come with a built-in rechargeable battery. When it wears out after a few years, it can no longer absorb enough energy. It drains quickly and turns off the thermostat. However, as discharged batteries charge as quickly as they deplete, this will result in the thermostat cycling on and off as the battery discharges and charges.

The solution

The only way to fix this problem is to replace the thermostat.

Reason3 - Problems related to backups

Since power for the HVAC system is transmitted through the HVAC fuse, a blown fuse will affect the entire system.

A)blown fuse

The problem

A blown fuse means there is no power to the thermostat or its built-in battery. And, as explained earlier in this article, a dead battery will cause the thermostat to cycle on and off. If you don't fix a blown fuse, over time the internal battery will completely discharge and the thermostat will shut off completely.

The solution

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Locate your system backup. It is usually connected to the control unit of your air conditioner. Disconnect power to your HVAC system and remove the fuse. After removing the fuse, look at the U-shaped wire visible through the clear fuse "window". The fuse blows when the U-wire breaks.

If the fuse is blown, replace it. Remember, when replacing the fuse, you must replace it with the same model as the one that blew. The color of a fuse is also important as it indicates the amperage.

After replacing the blown fuse, turn the system back on, and if the thermostat stops working after about two hours, the problem is solved.

Important note

If you have replaced the blown fuse and it has blown again when you turn the system back on, it is recommended that you contact an authorized technician to rule out and correct any problems.

B)Dirty fuse contact points

The problem

Even if the fuse is not blown, a dirty or loose fuse can cause intermittent power losses that can keep the thermostat working.

The solution

If the fuse does not blow, clean the contact points on the fuse and inside the fuse holder and replace the fuse. Since a fuse is not an expensive component, it always makes sense to replace it.

After replacing the fuse, turn the system back on and after about two hours check that the cycle has stopped.

Reason4 - Issues related to placement

A)Near other heat sources or in direct sunlight

The problem

A heat source such as a lamp, stove, kettle, toaster or TV screen, or exposure to direct sunlight can cause the thermostat to cycle on and off frequently. Heat from a source in your home or direct sunlight can transmit an inaccurate temperature to the thermostat. This high temperature reading can give the impression that it is overheating. The false impression of overheating forces the thermostat to turn off while trying to protect its components. When the heat source is turned off or direct sunlight is blocked, the thermostat will click again. You experience it like a thermostat that is constantly turning on and off.

The solution

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These inaccurate superheat readings can be easily corrected. Simply place the thermostat in a location where it is not near a direct heat source or in direct sunlight.

Reason5 - Problems related to the software

A)need updates

The problem

Like all smart devices, your Nest Thermostat will need software updates from time to time. If your thermostat starts behaving strangely, including turning on and off, it could be because the latest version of the software has not been installed.

The solution

A manual update can fix the cycle issue and keep your thermostat running smoothly. It's easy to update your thermostat. Just follow these steps:

  • Press snap ring onto thermostat.
  • Navigate to Settings.
  • Click on the Software tab.
  • Click on the Update tab.
  • Wait for the update to complete.

After updating the software, check that the system and thermostat are turned on, and after about two hours, check that the thermostat stops turning on and off. If it stopped, check the thermostat at least once a day for a few days to make sure the problem doesn't come back.

B)software bug

The problem

Even great thermostats like Nest thermostats can have glitches and software bugs. Different errors affect the thermostat differently. For example, a software glitch could cause the Nest Thermostat to cycle on and off. Other errors can affect the battery charge and cause it to drain faster than it should. The thermostat will begin to cycle on and off. These errors usually appear after a faulty or incomplete software update.

The solution

A software update usually eliminates software bugs. If you find that you still have active bugs after your last update, it's best to consult a Nest expert.

Reason6 – Other problems related to the HVAC unit

If your troubleshooting efforts related to the wiring, battery, fuse, thermostat, and software are unsuccessful, the problem could be a failure in one or more HVAC devices.

A faulty HVAC device can cause your Nest Thermostat to behave strangely, such as: B. if it is turned on and off frequently. This usually happens because the device is preventing the Nest Thermostat from drawing enough power from the HVAC system.

Unfortunately, to find and repair the faulty device in the HVAC system, you will need to call in an HVAC technician to run tests on the system. Depending on the test results, the technician may be able to fix the problem or replace the faulty device.

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Even sophisticated, well-designed thermostats like Nest thermostats can develop issues that turn them on and off. Fortunately, you can fix the problem yourself. In most cases, you can solve the problems yourself instead of having to call a qualified technician every time.

Remember to turn off the HVAC system, including the thermostat, before beginning the troubleshooting and repair process.


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2. How To Turn Off Nest Thermostat
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3. How To Fix a Nest Thermostat That Keeps Going Offline
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4. Nest Thermostat No C Wire Problem and Solutions
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5. Nest Thermostat Manual (MUST WATCH IF YOU HAVE A NEST)
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