How To Fix Nest Thermostat Error n72?

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Last Updated on 4 weeks
Nest Thermostat Error n72

The Nest thermostat has been a people’s favorite addition to the list of efficient heating devices.

This is because its intelligent mechanism allows the thermostat to learn the patterns of your heating requirements and it prepares a schedule for your needs according to the knowledge gathered. You can also control the thermostat from a smartphone or a smart speaker.

However, the thermostat functions on complex machinery. This means that there are several things that could go wrong with the wiring or other aspects of the thermostat.  

The error codes N72 or E74 are for the same issue and they indicate an issue with the power supply to the Rh wire on the thermostat.

In this article, we will discuss how to fix Nest thermostat error N72.

Let’s discuss the different aspects of the issue and the solutions that you can use to redirect power to the R wire on the thermostat in the next section.


Fixes For error code N72 on the Nest thermostat


The issue with the thermostat when you witness the error code N72 is, that the R wire on the thermostat is not receiving enough power.

The R wire is responsible for providing power to the thermostat from the transformer. Reasonably, this is a big issue for the thermostat and hence, it needs to be cleared as soon as possible.

Fix 1: Reset the thermostat

Before getting into any serious wiring changes, let’s begin with the simple solutions for the issue.

If the issue is with the settings on the Nest thermostat, it will help to restart the device. This clears any issues with the settings and any minor glitches are eliminated.

An easy way to do this is, just to disconnect the wire to the thermostat and wait for a while before reconnecting it.


Fix 2: Run diagnostic tests for the thermostat

There is an option for running self-tests on the thermostat to troubleshoot the issue. The smart mechanism of the Nest thermostat will let you know the problem with the device after you complete the test on the device.


Fix 3: Check if the power outlet is working

The power outlet that you have connected the thermostat to, should be working properly to supply the designated power to the thermostat.

Due to the functions that it performs, the thermostat also needs to receive more electrical power than any other small device.

Connect another device to the power outlet to check if the outlet is working. If it is not, connect the Nest thermostat to another outlet or get this one repaired.


Fix 4: Check the wires that are connected to the thermostat

The thermostat is connected to the power outlet through wires. If the wires are not connected securely or are broken, the thermostat will not function.

You will receive issues with the power distribution to any part of the thermostat and it will not only be limited to the R wire.

Check the wiring and replace the damaged wires if any.


Fix 5: Clean the drain pipes for the thermostat

The thermostat also has drain pipes to let out the water from the device. This condensate is really important to remove from the device to maintain its safety.

The drain pipes should be free of any debris and there should be no blockages in the pipe. Open the machinery after disconnecting the thermostat from the power source and clean the drain pipes.


Fix 6: The HVAC float switch is on

The HVAC float switch on the thermostat is a safety precaution. If there is excess water in the pan, the switch turns on and the power to the thermostat is cut off.

This is a safety measure so that there are no electrical accidents on the thermostat due to the excess water in the pan.

Check the HVAC float switch and if you find that it has been turned on, check for excess water in the machinery.

Contact a technician to take a look at further issues with the HVAC float switch if it has been turned on without a valid reason.


Fix 7: The HVAC relay coil is malfunctioning

The HVAC relay coil is also an important part of the thermostat machinery. When the R wire is not receiving power, it could be because the relay coil is malfunctioning and it has caused the fuse to blow.

Check the fuse as well and replace it if it has blown.


Fix 8: Contact a technical assistant

We have mentioned the solutions that can help you get rid of the error code without getting into too many technical details.

After all, the thermostat is a complex electrical machine and you can only control so much on your smartphone. 

Contact personnel to help you with the complex repairs on the machinery. You can even contact company support if the device is under warranty.

This will help you with free repairs and replacements on the device if there is extensive damage.


To conclude


There are many reasons for the R wire on the Nest thermostat to not receive enough power. We have mentioned all of them and the solutions that can help you get rid of the error code on your own.

However, you should be careful with the repairs on the device that function with complex electrical wiring. If you do not know how to handle the wiring, leave the repair to the professionals. It will also prevent you from making any mistakes on the device due to less knowledge.

We hope that we provided you with relevant advice on the error code N72 on the Nest thermostat. Keep following for more technical advice. 

Keep warm!!


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A Digital Marketer by profession and a passionate traveller. Technology has been always my first interest, so I consistently look for new updates in tech to explore, and also has expertise in WordPress.