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

When it comes to maintaining a comfortable temperature inside the house, a thermostat that performs smoothly is what we need. But what if you find out your Nest thermostat is not working because it cannot detect wires? 

There are several reasons why a Google Nest thermostat may not detect wires, including loose or disconnected wires, incompatible wiring, or a faulty thermostat. You must check the wiring connections, ensure the wiring is compatible with the thermostat, and follow the user manual for proper installation.

If nothing works, consider resetting the thermostat as a last resort. In this article, we will discuss all the reasons behind a Nest thermostat not detecting the wires and provide detailed information about troubleshooting it. 

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Why is Google Nest Thermostat not detecting any wires?

Numerous reasons are responsible for a thermostat not detecting any wires.

This section will discuss some of the common reasons behind a Nest thermostat not detecting the wires and how to solve them:

1. Damaged or corroded wires

When your thermostat is not detecting any wires, open the display and check the wire conditions.

The thermostat cannot detect the wires if the wire ends have been damaged or corroded.

Over time, the wires get old, get exposed to moisture, and become weak.

Sometimes, improper installation is also responsible. 

One way to fix the damaged or corroded wires is to strip and fix them.

Here are the steps:

  1. Turn off the power at the breaker. It will protect your HVAC and the thermostat from damage.
  2. Remove the display from the base.
  3. Pull out one wire from the device and inspect it. The wire you expose should be around ⅓ to ½ inch long. It should be clean and straight.
  4. Cut and re-strip the damaged or corroded wire ends. Ensure not to cut too much, as that will shorten the wire, and the detection problem will not get solved.
  5. Now, re-insert the wire into the thermostat. Keep the connector’s button down. If the wire is not fully inserted into the connector, the device will again fail to detect it.
  6. Repeat these steps with each wire until all of them are fixed. 
  7. Check all the wire connections and push the display back into the device. 
  8. Turn on the power back and check your thermostat. 

Call a Nest professional to replace the wires if you can’t fix it yourself.

2. Incompatible wires

The Google Nest thermostat needs a separate wire type from the other thermostats.

The device will need solid-core low-voltage copper wires. 

The device will not support any stranded wires. 

If you have low-voltage stranded wires, the device cannot detect them inside.

Stranded wires are expected when you have old wiring in your house and have not replaced them. 

For the time being, reinstall your old thermostat. 

Call a professional and get them replaced with solid-core low-voltage copper wires.

3. Small wires

The best size of wires for the Google Nest thermostats range between 18 and 22 gauges. 

These are the standard sizes for heating and cooling systems.

If the wires are smaller than the mentioned size, the device cannot detect them.

Thin wires, too, will not get detected by the thermostat. 

It happens when you incorrectly install the wires or the wiring is outdated.

To fix this, you need an expert’s help. He will change the wires. 

4. Misconfigured wires

Suppose your Nest thermostat is detecting a wire in a connector where you haven’t installed the wire but not detecting where you have connected. 

In that case, there has been a misconfiguration. 

You might have made this mistake during some DIY wiring projects, during the initial setup process, or when you have recently had a wire repair. 

To fix the problem, open the display, see which connections you have reversed, and fix them.

If you cannot understand the wire configuration, call a Nest professional to deal with the matter.

5. Dirty base plate or loose wire connections

This part confused me at first. But after consulting a Nest expert, I now know why checking the base plate is essential.

The base plate of the thermostat attaches to the wall and contains numerous holes to connect the thermostat to the wires from the HVAC of your house. 

The wires need to be appropriately connected and inserted into the base plate. 

Partial or loose insertion of the wires means your device will not detect the wires. 

To fix the problem, turn off the power at the breaker and check the base plate by removing the thermostat from the wall. 

Check for loose wire connections. 

If there are any loose wires, disconnect them, secure and tighten them, and reconnect them. 

Then, check the thermostat. 

Once, my Nest thermostat had a problem detecting wires despite secured connections.

While examining closely, I discovered the base plate was dirty. 

I cleaned it, rechecked the connections, and started the thermostat. 

Surprisingly, it started to detect all the wires.

After some research and expert consultation, I realized that the dirty base plate was the reason. 

When the base plate develops excessive layers of dirt and debris, they stop your device from having proper contact with the wires. 

So, cleaning the base plate with a soft cloth will solve the problem. 

6. Software updates

The Google Nest thermostats run on software like mobile phones.

This software must stay updated. Usually, these get auto-updated timely. 

You can understand this when your thermostat blinks a green light. 

But if the update gets late, the thermostat will create issues; failing to detect the wires is one of them.

So, check the software update once when you notice that the thermostat is not detecting the wires despite no wire-related issues.

If there’s an update, download and restart your thermostat.

To update the thermostat:

  1. Select SETTING in your thermostat. 
  2. Click on the SOFTWARE option. 
  3. You will see the software version and the one you need to update, if any. 
  4. Click on the UPDATE. The thermostat starts checking for updates.
  5. If there is a new version, click on DOWNLOAD and install it. 
  6. Once you finish this, check whether your thermostat is working or not.

To update from the mobile app:

  1. Open the phone app with which you control the device.
  2. Choose the Nest thermostat. 
  3. Select NEST SETTINGS 
  4. Click on the VERSION or SOFTWARE to check for updates. 
  5. If there is any update available, it will pop up. 
  6. Click on it and download it.

After you update the thermostat software, it should return after 1-2 minutes. 

The thermostat might get frozen while updating if it doesn’t turn on even after 15 minutes. 

In that case, remove and reconnect the display. 

Pull it off from the base, ensuring the pin connector stays lined up. 

Push it back in place. 

If there is a click sound, you have done it correctly. 

If this doesn’t help, consult the manual or expert. 

7. Compatibility of thermostat with HVAC systems

The thermostat needs to be compatible with the HVAC system of your house. 

If they are incompatible, the thermostat will not be able to detect the wires of the heating and cooling systems. 

As a result, you won’t receive any heat or cooling, and the thermostat will no longer work.

So, it would be best to assure that they are compatible. 

Remember that 85% of the Google Nest and Nest E thermostats are compatible with the HVAC systems, and 95% of Google Nest Learning thermostats are compatible with the HVAC systems. 

Also, the Nest Learning thermostats are primarily compatible with the 24V and old HVAC systems running on natural gas, oil, and electricity.

Knowing this will make selecting the compatible thermostat for your house’s central heating and cooling systems easier. 

8. Old age or faulty device 

Over time, the thermostat will become old and wear out due to daily usage. 

So, at one point, it will malfunction and stop detecting the wires despite their presence and proper connection. 

Try checking the wires once – their connection, size, compatibility, and everything else. 

If everything is fine, the device might be the problem.

If your device has lasted only a few months, it has some manufacturing fault. 

Call a professional to get it fixed.

If the device has been over 10 years old, it is time to replace it with a new one. 

What if everything is fine with your thermostat?

Despite ruling out all the problems, the thermostat will still fail to detect the wires. 

It might happen because of some technical fault or error. 

You can quickly solve this by restarting or resetting your thermostat. 

To restart your thermostat:

  1. Press the thermostat ring and go to the QUICK VIEW menu. 
  2. Find the thermostat ring on the Nest device. 
  3. Then, go to the SETTINGS. 
  4. Go to RESET and press SELECT. 

If the display freezes, press the ring and hold it for 10 seconds. 

Leave and press it again and return to the thermostat. 

You can try a soft reset:

  1. Push the thermostat ring for 10 seconds until the light stops blinking. 
  2. Wait for 10 seconds.
  3. Push the ring again for 10 seconds and start the device. 

If you need a hard reset, remember you are factory resetting it.

However, you will have options to choose which settings you have to reset anew:

  1. Open the QUICK VIEW menu and press the Nest ring. 
  2. Select SETTINGS when the ring turns.
  3. Select the ring and then PRESET. 
  4. Now, choose the options you want to reset – HOME or AWAY, SCHEDULE, NETWORK, ALL SETTINGS, etc. 
  5. Click on the ring and activate the resetting.

To reset the Nest thermostat manually:

  1. Remove the thermostat from the base.
  2. Then remove the batteries for a few seconds.
  3. Put them back and press the device until you hear a clicking sound.
  4. After some time, it will turn on. 

To reset Nest E and Nest Learning:

  1. Press the thermostat down for 10 seconds until the screen goes off, and release it.
  2. Press and release the ring to turn back the device on and complete the restart process. 
  3. The Nest logo will be seen, and the screen will turn on as the restart finishes.

When to call the Nest support team?

Calling the Nest support team for help is the last option you have to fix the thermostat that is not detecting any wires. 

When you cannot find any of the above problems in your thermostat, there might have been some technical or hardware issues that need an expert’s attention. 

Besides, it is better to let the professionals handle any problem with your thermostat if you are already under warranty. 

The professionals can deal with it better and even change the unit to another without letting you spend a lot of money. 

Trying to troubleshoot the problem will take a lot of time and effort. 

And, there is no guarantee that you will be doing it without increasing any further damage. 

So, this is another reason to let experts deal with it. 

Besides the money, the experts will quickly understand the problem in your device and fix it within no time. 

If your device’s warranty is over, you can try troubleshooting. 

But until then, let the professionals handle everything. 

Inform the professionals about the thermostat’s problems and the troubleshooting steps if you have attempted any. 

Understanding and dealing with the situation will be easy for them. 

Final thoughts

When the Google Nest thermostat fails to detect wires, most of the reasons are wire-related, for instance, corroded or damaged wire ends, tiny wires, misconfigured wires, and incompatible stranded wires. Other reasons are outdated software, dirty base plate, loose connections, incompatible HVAC systems, and old or defective thermostats.

First, rule out the wire-related problems and then check for the others. Use a compatible thermostat for your HVAC system. Check the base plate and ensure that you have connected the wires tightly and the plate is not too dirty. If it is, clean it with a cloth. As for the defective thermostat, contact a professional if your device has been for a few months, or get a new one if it is over 10 years old. 

If everything is fine in your thermostat, there must have been some error for which the device is not detecting the wires. So, try restarting or resetting your thermostat once. If you still cannot fix it, reinstall the old thermostat for the time being and call a professional for further assistance. 

What does the E73 error mean in the Nest thermostat?

When your thermostat shows this error, it cannot detect the Rc wire. The reasons might be incorrect wiring or loose connection, dirty air filters, clogged drain tubes, pans, or an inoperative HVAC fuse.

Why is C wire necessary for the Nest thermostat?

The C wire is essential for smart Wi-Fi thermostats as it gives them power. If the wire goes undetected, your thermostat will not receive any power for operation. 

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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