Troubleshoot Nest thermostat error codes

You might see an error on your Google Nest thermostat or in the app if there’s a problem detected with the thermostat’s wiring or internet connection. Here are some errors you can see and steps you can take to help fix them.

Summer 2019 heat wave troubleshooting

If your Nest thermostat suddenly started showing an E3E4E23E24E73E74 or E195 power error during the hot summer months, visit the following link to learn how to help fix it.

Troubleshooting E3, E4, E23, E24, E73, E74 and E195 errors >

If you see any other thermostat error, read below.

 

How to troubleshoot T errors 

You’ll see a Nest thermostat T error when running a system test after you first install your thermostat. The most common reasons for T errors are that wires are in the wrong thermostat connectors or the wires aren’t fully inserted into the thermostat connectors.

For detailed troubleshooting steps, please see Troubleshooting Nest thermostat T error codes during a System Test.

General information about E errors 

E errors are critical and must be fixed as soon as possible. Your thermostat won’t allow you to control heating or cooling, and the error message won’t go away until the cause has been fixed.

Look at the table below and select your specific error code for troubleshooting help. You can also contact a local Nest Pro.

Caution: It's important to protect you, your system, and your thermostat. Turn off the power to your system at the fuse box before exposing or adjusting any wiring.

General information about N errors

N errors aren’t critical and in most cases you can still use your thermostat, but some features may not work, or they won't work as expected, and you’ll see the error in the app. If you're not able to control your heating or cooling with your thermostat, you should try to fix the issue as soon as possible.

Look at the table below and select your specific error code to see if you need to contact a local Nest Pro to help resolve your issue.

Caution: It's important to protect you, your system, and your thermostat. Turn off the power to your system at the fuse box before exposing or adjusting any wiring.

 

Troubleshoot your error code

Type your error code (no spaces) in the box below to get help.

Error codeError meaning

N1, N21 & N71

Power wire Rc detected. Not connected to equipment.

Your Nest thermostat isn't electrically detecting your Rc wire, but one is connected to the Nest thermostat base.

Troubleshoot a N1 error

Troubleshoot a N21 error

Troubleshoot a N71 error

N2, N22 & N72

Power wire Rh detected. Not connected to equipment.

Your Nest thermostat isn't electrically detecting your Rh wire, but one is connected to the Nest thermostat base.

Troubleshoot a N2 error

Troubleshoot a N22 error

Troubleshoot a N72 error

N3, N23, N73 & N153

No power to W1 wire detected.

Your Nest thermostat isn't electrically detecting your W1 wire, but one is connected to the Nest thermostat base.

Troubleshoot a N3 error

Troubleshoot a N23 error

Troubleshoot a N73 error

N4, N24, N74 & N154

No power to Y1 wire detected.

Your Nest thermostat isn't electrically detecting your Y1 wire, but one is connected to the Nest thermostat base.

Troubleshoot a N4 error

Troubleshoot a N24 error

Troubleshoot a N74 error

N5, N25 & N75

No power to W2/AUX wire detected.

Your Nest thermostat isn't electrically detecting your W2/AUXwire, but one is connected to the Nest thermostat base.

Troubleshoot a N5 error

Troubleshoot a N25 error

Troubleshoot a N75 error

N6, N26, N76 & N156

No power to G wire detected.

Your Nest thermostat isn't electrically detecting your G wire, but one is connected to the Nest thermostat base.

Troubleshoot a N6 error

Troubleshoot a N26 error

Troubleshoot a N76 error

N7, N27 & N77

No power to O/B wire detected.

Your Nest thermostat isn't electrically detecting your O/B wire, but one is connected to the Nest thermostat base.

Troubleshoot a N7 error

Troubleshoot a N27 error

Troubleshoot a N77 error

N28 & N78

No power to Y2 wire detected.

Your Nest thermostat isn't electrically detecting your Y2 wire, but one is connected to the Nest thermostat base.

Troubleshoot a N28 error

Troubleshoot a N78 error

N29, N79 & N159

No power to wire detected.

Your Nest thermostat isn't electrically detecting your wire, but one is connected to the Nest thermostat base.

Troubleshoot a N29 error

Troubleshoot a N79 error

M12

The temperature sensor is placed in an area that’s much colder or hotter than where your thermostat is installed.

Troubleshoot an M12 error

M13

Your Nest thermostat may be wired incorrectly, or your system may be incompatible.

Troubleshooting E66, E116, E196, and M13 errors

W1

The Nest thermostat can't continue to connect to your Wi-Fi network.

Your Wi-Fi access point may not fully support a Wi-Fi standard known as power saving mode.

Troubleshoot a W1 error

W2

Failed to connect.

Your Wi-Fi access point may have security settings enabled that prevent your Nest thermostat from connecting.

Troubleshoot a W2 error

W3

Failed to connect.

Your Wi-Fi access point is not providing a network IP address to your Nest thermostat.

Troubleshoot a W3 error

W4

Failed to connect.

The Nest thermostat is connected to your wireless network but not to the Internet.

Troubleshoot a W4 error

W5

Failed to connect.

Your Nest thermostat can't connect to Wi-Fi.

Troubleshoot a W5 error