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 heat wave troubleshooting
If your Nest thermostat shows an E3, E4, E23, E24, E73, E74 or E195 power error during the hot summer months, visit g.co/nest/summerhelp to learn how to fix it.
If you see any other thermostat error, read below.
T error codes
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.
E error codes
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 pro for other issues (including HVAC).
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.
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1st gen |
2nd gen |
3rd gen |
Thermostat E |
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E22 |
E42 |
E72 |
E94 |
E155 |
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N error codes
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 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.
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1st gen |
2nd gen |
3rd gen |
Thermostat E |
TD error codes
General information about TD error codes
W error codes
M error codes
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Error code |
Troubleshooting |
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Common wire ("C" wire) is required. |
You may need to update your Nest thermostat's software or attach a common wire. Make sure your thermostat is connected to Wi-Fi.
Learn about the common wire and why a Nest thermostat may need one > |
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No power wires detected. Rc or Rh wire required. |
The Nest thermostat isn't physically detecting your Rc or Rh wire or one isn't attached. Or power wires are physically detected, but the Nest thermostat isn't detecting power to the Rc or Rh wire. Either Rc or Rh must be connected for your Nest thermostat to work. |
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No power to Rc wire detected. |
The Nest thermostat isn’t electrically detecting your Rc wire. These errors can be caused by different things depending on the weather:
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No power to Rh wire detected. |
The Nest thermostat isn’t electrically detecting your Rh wire. These errors can be caused by different things depending on the weather:
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No heating or cooling detected. W1 or Y1 wire is required. |
The Nest thermostat isn't physically detecting your a W1(heating) or Y1 (cooling) wire. One of these wires is required for any type of system that the Nest thermostat supports. |
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Too many wires detected. Please remove at least one of O/B, W1, Y1 or AUX. |
The Nest thermostat doesn't support the configuration of wires you've attached. |
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Y1 wire not detected. A heat pump requires a Y1wire. |
Your Nest thermostat is physically detecting a wire in the O/Bconnector, which means that you have a heat pump system. Heat pumps require a Y1 wire to be connected. |
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Additional wire(s) required. W2/AUX detected by itself. |
Your Nest thermostat is physically detecting a wire in the W2/AUX connector. Supported configurations that use this connector also include a W1 (heating) wire or an O/B + Y1 wire. |
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No power to C wire detected. |
Your Nest thermostat is physically detecting a wire in the C(common) connector but isn't detecting any power to it. |
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No power to Y1 wire detected. |
Your Nest thermostat is physically detecting a wire in the Y1(cooling) connector but isn't detecting any power to it. |
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Heat pump wire O/Bdetected. No heat pump system present. |
Your Nest thermostat is physically detecting a wire in the O/B(heat pump) connector but isn't detecting any power to it. You may need to update your Nest thermostat's software. Make sure your thermostat is connected to Wi-Fi.
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No power to W1 wire detected. |
Your Nest thermostat is physically detecting a wire in the W1(heating) connector but isn't detecting any power to it.
Contact a local pro if you need more help. |
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A heat pump can have at most one auxiliary heat wire. |
Your Nest thermostat was previously setup as a single fuel system with auxiliary heat, but it's detecting both W1 and W2/AUX wires. Single fuel heat pump systems support a wire in either W1 or W2/AUX but not in both at the same time. |
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Dual fuel requires an alternate heat wire. |
Your Nest thermostat was previously set up as a dual fuel system, but it's not detecting a W1, W2/AUX or (W3). One of these wires is required in order to have alternate heat. |
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Dual fuel can have at most two alternate heat wires. |
Your Nest thermostat was set up as a dual fuel system, but the W1, W2/AUX and (W3) wires are configured as alternate heat wires. |
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A heat pump can have at most one auxiliary heat wire. |
Your Nest thermostat was previously set up as a single fuel system with auxiliary heat, but it's detecting W1, W2/AUX and (W3) wires. Single fuel heat pump systems support a wire in only one of these connectors. |
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A heat pump can have at most one auxiliary heat wire. |
Your Nest thermostat was previously set up as a single fuel system with auxiliary heat, but it's detecting W1 and (W3) wires. Single fuel heat pump systems support a wire in either W1 or (W3) but not in both at the same time. |
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A heat pump can have at most one auxiliary heat wire. |
Your Nest thermostat was previously set up as a single fuel system with auxiliary heat, but it's detecting W2/AUX and (W3) wires. Single fuel heat pump systems support a wire in either W2/AUX or (W3) but not in both at the same time. |
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Y2 wire without Y1 wire. |
Your Nest thermostat is physically detecting a Y2 wire but not a Y1 wire. Both wires are required for 2 stage conventional cooling systems or 2 stage heat pumps. |
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W3 wire without W2/AUXwire. |
Your Nest thermostat is physically detecting a (W3) wire but not a W2/AUX wire. Both wires are required for 3 stage conventional heating systems. |
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E wire without O/B wire. |
Your Nest thermostat is physically detecting a (E) wire but not an O/B wire. O/B is a heat pump wire and the Nest thermostat only supports the use of emergency heat with heat pump systems. |
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E42, E43, E44, E45, E46, E47, E48, E49, E50, E51, E92, E93, E94, E95, E96, E97, E98, E99, E100, E101 Please contact Nest support to help troubleshoot this error. |
Your Nest thermostat either has wires that aren't fully inserted into the connectors or has tripped an internal fuse. Please contact Nest support to help troubleshoot this error. |
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E52, E53, E54, E55, E56, E57, E58, E102, E103, E104, E105, E106, E107, E108, E182, E183 & E188 The Nest thermostat has an overcurrent error. |
There is a problem with the Y1 wire. Your thermostat is not receiving power from your system. |
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No power to Y1 wire detected |
Your Nest thermostat may be wired incorrectly, or your system may be incompatible. |
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G2 detected. G1 wire is also required. |
Your Nest thermostat is physically detecting a G2 (fan) wire in the Y2 connector, but it’s not detecting a wire in the Gconnector. Both wires are required for a multi-speed fan. Contact a local pro if you need more help. |
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G2 wire detected. Remove W2/AUX wire. |
Your Nest thermostat is physically detecting a wire in the W1connector, a wire in the AUX/W2 connector, and a G2 (fan) wire in the Y2 connector. This indicates you have more than one stage of heat and more than one fan speed. The Nest thermostat does not support multiple stages of heat and multiple fan speeds at the same time. Contact a local pro if you need more help. |
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G2 wire detected. Remove E wire. |
Your Nest thermostat has detected a G2 (fan) wire in the Y2connector, and an emergency heat wire in the connector. The Nest thermostat doesn’t support a multi-speed fan and emergency heat together. Contact a local pro if you need more help. |
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G wire detected. G1 and G2also required. |
Your Nest thermostat is physically detecting a G3 (fan) wire in the connector, but it isn’t detecting a G2 (fan) wire in the Y2connector or a wire in the G connector. All three wires are required for a three speed fan. Contact a local pro if you need more help. |
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G2 and O/B wire conflict. |
Your Nest thermostat has detected a G2 (fan) wire in the Y2connector, and a wire in the O/B connector. This wiring indicates a multi-speed fan and a heat pump. The Nest thermostat doesn’t support this kind of system. Contact a local pro if you need more help. |
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Y1 wire not detected. |
The Nest thermostat isn't physically detecting your Y1 wire or one isn't attached. A wire in your O/B terminal is configured as a Heat Pump O/B wire. Heat Pumps require a Y1 wire to function. Take your thermostat display off the wall and check your wires. Contact a local pro if you need more help. |
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W1 wire not detected. |
The Nest thermostat isn't physically detecting your W1 wire or one isn't attached. A wire in your O/B terminal is configured as a second stage of heat. Your Nest thermostat needs a first stage of heat (W1) to use a second stage of heat. Take your thermostat display off the wall and check your wires. Contact a local pro if you need more help. |
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R wire not detected |
The Nest thermostat isn't physically detecting your R wire or one isn't attached. An R wire must be connected for your Nest thermostat to work. Take your thermostat display off the wall and check your wires. Make sure the R wire is fully inserted into the R connector on your Nest Base. Contact a local pro if you need more help. |
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No power to R wire detected. |
The Nest thermostat isn’t electrically detecting your R wire.
Contact a local pro if you need more help. |
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Error code |
Troubleshooting |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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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. |
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No power to wire detected. |
Your Nest thermostat isn't electrically detecting your wire, but one is connected to the Nest thermostat base. |
W error codes
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Error code |
Troubleshooting |
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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. |
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Failed to connect. |
Your Wi-Fi access point may have security settings enabled that prevent your Nest thermostat from connecting. |
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Failed to connect. |
Your Wi-Fi access point is not providing a network IP address to your Nest thermostat. |
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Failed to connect. |
The Nest thermostat is connected to your wireless network but not to the Internet. |
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Failed to connect. |
Your Nest thermostat can't connect to Wi-Fi. |