Troubleshooting 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 E3, E4, E23, E24, E73, E74 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.

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 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.

1st gen	2nd gen		3rd gen		Thermostat E
E1 E2 E3 E4 E5 E6 E7 E8 E9 E10 E11 E12 E13 E14	E22 E23 E24 E25 E27 E28 E29 E30 E32 E33 E34 E35 E36 E37 E38 E39 E40 E41	E42 E43 E44 E45 E46 E47 E48 E49 E50 E51 E52 E53 E54 E55 E56 E57 E58 E66	E72 E73 E74 E75 E77 E78 E79 E80 E82 E83 E84 E85 E86 E87 E88 E89 E90 E91 E92 E93	E94 E95 E96 E97 E98 E99 E100 E101 E102 E103 E104 E105 E106 E107 E108 E109 E110 E111 E112 E113 E116	E155 E157 E158 E159 E160 E162 E164 E169 E182 E183 E184 E188 E194 E195 E196

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 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.

1st gen	2nd gen	3rd gen	Thermostat E
N1 N2 N3 N4 N5 N6 N7	N21 N22 N23 N24 N25 N26 N27 N28 N29	N71 N72 N73 N74 N75 N76 N77 N78 N79	N153 N154 N156 N159

W error codes

W1
W2
W3
W4
W5

M error codes

M12
M13

Error code

Troubleshooting

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.

Press your thermostat's ring to open the Quick View menu.
Select Settings .
Choose Network.
Your thermostat will take a moment to scan for available networks. Choose your home Wi-Fi network from the list.
Enter your password if prompted. Once connected to Wi-Fi, your thermostat can automatically install updates.

Learn about the common wire and why a Nest thermostat may need one >

E2, E22 & E72

No power wires detected. Rc or Rh wire required.

The Nest thermostat isn't physically detecting your Rc or Rhwire 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.

Troubleshoot an E2 error

Troubleshoot an E22 error

Troubleshoot an E72 error

E3, E23 & E73

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:

If it’s summer or there’s a heat wave, read this article first: Troubleshooting during the summer

If it’s winter or there’s a cold snap, or if it's mild weather, select your error below:

E4, E24 & E74

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:

If it’s summer or there’s a heat wave, read this article first: Troubleshooting during the summer

If it’s winter or there’s a cold snap, or if it's mild weather, select your error below:

E5, E25, E75 & E155

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.

Troubleshoot an E5 error

Troubleshoot an E25 error

Troubleshoot an E75 error

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.

Troubleshoot an E6 error

E7, E27 & E77

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.

Troubleshoot an E7 error

Troubleshoot an E27 error

Troubleshoot an E77 error

E8, E28 & E78

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.

Troubleshoot an E8 error

Troubleshoot an E28 error

Troubleshoot an E78 error

E9, E29, E79 & E159

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.

Troubleshoot an E9 error

Troubleshoot an E29 error

Troubleshoot an E79 error

E10, E30, E80 & E160

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.

Troubleshooting E10, E30, E80 and E160 error codes

E11

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.

Press your thermostat's ring to open the Quick View menu.
Select Settings .
Choose Network.
Your thermostat will take a moment to scan for available networks. Choose your home Wi-Fi network from the list.
Enter your password if prompted. Once connected to Wi-Fi, your thermostat can automatically install updates.

E12, E32, E82 & E162

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.

Turn off the power to your heating and cooling system at your breaker.
Grip the metal ring of your thermostat and pull it gently towards you away from the wall. Your thermostat should pop right off the base.
Remove the wire in the W1 terminal, straighten it, and put it back in as far as it will go. You may need to strip the end of your wire to make sure enough copper is exposed.
Reattach your thermostat to the baseplate and turn the power back on at your breaker.
If you still see the error message, you should contact a professional to diagnose issues with your heating system.

Contact a Nest Pro >

E13, E33 & E83

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.

Troubleshoot an E13 error

Troubleshoot an E33 error

Troubleshoot an E83 error

E14, E34, E84 & E164

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.

Troubleshoot an E14 error

Troubleshoot an E34 error

Troubleshoot an E84 error

E35, E85

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.

Troubleshoot an E35 error

Troubleshoot an E85 error

E36, E86

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.

Troubleshoot an E36 error

Troubleshoot an E86 error

E37, E87

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.

Troubleshoot an E37 error

Troubleshoot an E87 error

E38, E88

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.

Troubleshoot an E38 error

Troubleshoot an E88 error

E39, E89 & E169

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.

Troubleshoot an E39 error

Troubleshoot an E89 error

E40, E90

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.

Troubleshoot an E40 error

Troubleshoot an E90 error

E41, E91

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.

Troubleshoot an E41 error

Troubleshoot an E91 error

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.

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.

Troubleshoot E52 – E58

Troubleshoot E102 – E108

E66, E116 and E196

No power to Y1 wire detected

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

Troubleshooting E66, E116, E196, and M13 errors

E109

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.