How To Fix Trane thermostat error code 126?

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Trane Thermostat Error Code 126

Well, thermostats are a necessity for many. It is great that in today’s world we can change the living temperatures according to our convenience and do not have to adjust according to the temperature.

The cherry on the cake with the advancement of the internet age is the Internet of Things. There are so many regular appliances that now provide you with better function because they have the ability to connect to the internet.

Trane Thermostats are people’s favorite because of this exact same reason. They are ‘Smart Thermostats’.

Do you need to be smarter to handle these appliances? Well, looking at the extensive technology they use, anything can go wrong at any point, and then you do need to be smart to navigate through the error.

In this article, we will discuss how to fix Trane Thermostat error code 126. You do need to be smart to fix the error but assistance can always be found when you are in need and we are here for the same reason.

So, let’s see what other users and the customer support team on Trane Thermostats advise for error code 126.

What is The error code 126 on Trane thermostats?

Different error codes assigned to the different issues with an appliance, help the users to get in touch with the exact issue that their device is facing.

Since the Trane thermostats can be controlled with any smart device you own, you will see the error code not only on the thermostat but also on the device that you are using to control the thermostat.

The error code 126 on Trane thermostats communicates a break in the electrical circuit or a low-temperature lockout.

This is also mentioned in the official guide that you get with the thermostat installation and also the official website of Trane thermostats is equipped with this information.

Reasons For the Trane thermostat error code 126

What are the different reasons that could be behind the low-temperature lockout on the Trane thermostat?

Well, there could be quite a few reasons that will perfectly explain the issue.

In this section, we will simply list the issues so that you can compare your device’s function to the list and find out what exactly you need to fix.

Here is why the error may appear.

  • The Furnance or the AC unit is not responding to the thermostat.
  • There has been a power surge that caused the thermostat to stop responding
  • The high voltage fuse on the outside unit has blown
  • Your outdoor transformer is not performing
  • There is a loose connection or a broken wire in the circuit

These five reasons are the most widely reported when we talk about error 126 on the Trane thermostat.

Now that we know the why, let’s move to the next section to understand these in more detail and suggest some fixes for the same.

How To Fix Trane thermostat error code 126?

As we have discussed, error code 126 on the Trane thermostat signals that the AC/furnace has stopped responding to the thermostat unit. This can happen for the reasons that are listed above.

Let’s discuss what has worked for other users.

Fix 1: Power Surge or Spike

If you have just experienced a spike in the voltage, this may have caused the fuse to blow or the connection to get interrupted.

In this case, mostly the issue lies with the fuse. The circuit breaks and unless you have expertise in electrical appliance management, you should contact the customer support team or a technician to handle this for you.

Fix 2: The furnace or the AC unit has stopped responding

When you receive the error message, it is likely that the issue lies with the AC unit or the furnace and the thermostat has not really been affected.

In this case, you can try a reset on the devices. The reset in this case is pretty simple and you just have to turn off the AC unit/furnace and the thermostat. Let them take a break for about a minute or so before turning them on again.

Now turn all the appliances back on again and see if the issue gets resolved.

Fix 3: There is a broken wire or a loose connection

Also, one of the easiest things to figure out on your own is if the connection to all the affected devices is secure.

If the connection is loose or there is a broken wire somewhere, it is a no-brainer that the circuit will not be complete and the devices will not respond.

Check the circuit to see if all the outlets and the plugs are functional. Check if the wires connecting them are broken.

If you find a broken wire, you should immediately replace it not just for the device’s function but also to eliminate the chances of stepping on a naked wire and getting electrocuted or burning your house to cinders with an ignored fire hazard.

Fix 4: The outdoor transformer is not working

Check for the outdoor transformer’s function.

In this case, it becomes very technical and you will need an expert to come in and look at the transformer to figure out the exact issue with it.

The issues with the transformer should also not be ignored as they can also cause a safety issue in the long run.

Fix 5: The Voltage fuse is blown

As we have mentioned in a point earlier, if you are experiencing this error after a power spike, you might have a problem with the blown fuse.

Check the outdoor unit to see if the fuse is blown. If you have expertise in replacing a fuse, you can attempt this yourself. Expert assistance here is recommended.

Fix 6: Contact the support helpline

When you know the exact cause of the error code on your device, you can contact the customer support team and give them the details.

They will suggest some basic fixes and guide you through the procedures that you can do alone.

If the issue seems severe, this is the place where you will get the best technical support. The company will send in a technician to help you.


The smart devices make it seem very easy to handle them but the reality is quite lopsided when you find an error on the system that is hard to get rid of.

The Trane thermostats are very compatible and have some easy fixes that you will find on the internet. We have made a list of the non-dangerous solutions that can be tried in isolation and have helped other users.

In any case, you are dealing with an electrical appliance and the behavior is quite unpredictable. If you feel like you are getting too deep into the process that you understand nothing about, always choose the safer option and call in a technician.

As they say, it is better safe than sorry.

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Falguni Rana is a technology writer who has expertise in software and hardware troubleshooting. She publishes how-to and troubleshooting guides for different apps, websites, games, and consumer hardware products.