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Google Nest thermostat error codes

Google Nest thermostat codes as Google Nest Help lists them, each with its meaning and the first safe check.

  • E1, E297
    The thermostat needs a common wire (C wire)
  • E11
    A heat pump wire (O/B) is detected, but
  • E13, E33, E36, E37, E38, E83, E86, E87, E88, E413
    Too many auxiliary heat wires are detected for
Exact codeDocumented meaningFirst safe checkVerificationStop condition
Part of Google Nest expanded error-code library

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Google Nest thermostat · exact code

Google Nest thermostat code E10, E30, E66, E80, E116, E160, E196, E296, M13: meaning and exact next steps

E10, E30, E66, E80, E116, E160, E196, E296, M13 means The thermostat detects no power to the Y1 wire, which Google labels a cold-weather shutoff. Nest thermostats can use the Y1 (air conditioner) wire to keep charged when there is no common wire, and an air conditioner's low-pressure safety switch can stop sending that power in very cold weather. Google also says the cause can simply be a system that needs maintenance.

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Google Nest thermostat code E109, E110, E111, E112, E113 and E439 to E443: meaning and exact next steps

E109, E110, E111, E112, E113 and E439 to E443 means The thermostat detects a conflict involving the G (fan) wires. Google words them as: G2 detected and G1 also required (E109, E439); G2 detected, remove the W2/AUX wire (E110, E440); G2 detected, remove the E wire (E111); G or G3 detected and G1 and G2 also required (E112, E442); G2 and O/B conflict (E113, E443).

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Google Nest thermostat code E12, E32, E82, E162: meaning and exact next steps

E12, E32, E82, E162 means The thermostat detects no power to the W1 (heating) wire.

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Google Nest thermostat code E14, E34, E84, E164, E264, E414: meaning and exact next steps

E14, E34, E84, E164, E264, E414 means A dual-fuel system (a heat pump with a backup furnace) needs an alternate heat wire, and the thermostat does not find one.

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Google Nest thermostat code E157, E158, E194: meaning and exact next steps

E157, E158, E194 means The thermostat does not detect an expected wire. Google words E157 as Y1 wire not detected, E158 as W1 wire not detected and E194 as R wire not detected.

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Google Nest thermostat code E2, E22, E72, E402: meaning and exact next steps

E2, E22, E72, E402 means The thermostat detects no power wires. Google says an Rc or Rh wire is required.

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Google Nest thermostat code E257, E258, E294: meaning and exact next steps

E257, E258, E294 means The wires were not configured properly in the Google Home app. Google words them as: heat pump requires Y1 wire (E257), W2 wire requires W1 (E258) and R wire is required (E294).

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Google Nest thermostat code E3, E23, E73, E195: meaning and exact next steps

E3, E23, E73, E195 means The thermostat detects no power to the Rc wire. Google's table words E195 as no power to the R wire.

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Google Nest thermostat code E450, E451, E452: meaning and exact next steps

E450, E451, E452 means A wiring conflict on the Nest Learning Thermostat (4th generation): E450 is an AQ and star wire conflict, E451 says dual transformers require the Y3 wire on AQ+, and E452 says Y3 requires Y2.

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Google Nest thermostat code E52, E102, E182 and the other overcurrent codes: meaning and exact next steps

E52, E102, E182 and the other overcurrent codes means The thermostat detected an overcurrent on one of its wires. Google says its internal breaker has tripped 10 or more times, which means a recurring problem that will not go away by itself. Which wire to check depends on the code: E52, E102 and E182 are W1; E53, E103 and E183 are Y1; E54, E104 and E184 are G; E55 and E105 are O/B; E56 and E106 are W2/Aux; E57 and E107 are Y2; E58, E108 and E188 are the star or star/O-B terminal.

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Google Nest thermostat code E8, E28, E78, E408: meaning and exact next steps

E8, E28, E78, E408 means Additional wires are required because a W2/AUX wire was detected by itself.

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Google Nest thermostat code H1, H2, H71, H72 and the other H codes: meaning and exact next steps

H1, H2, H71, H72 and the other H codes means A Heat Link problem on a system with a domestic hot water tank, OpenTherm, a condensing boiler, district heating or Fil pilote. H1, H71 and H151 mean the thermostat cannot connect to the Heat Link (its light is yellow); H2, H72 and H152 mean the thermostat lost power; H73 and H153 mean it cannot detect the system's OpenTherm; H155 means the Heat Link went offline when its batteries were low; H156 means OpenTherm wiring was set up without selecting OpenTherm; H157 and H158 mean the Heat Link was removed from the app or account.

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Google Nest thermostat code M13, M20, M22, M23, M26 and the other M codes: meaning and exact next steps

M13, M20, M22, M23, M26 and the other M codes means M codes are a mix of informational messages and problems, and Google's table points each to its own article: M13 is the cold-weather no-power code, M20 is a "No power" alert, M22 means the thermostat is offline, M23 means a thermostat wire is undetected or unconfigured, M26 means it cannot connect to a Matter device, M12 means a Nest Temperature Sensor is not in a good spot, M19 is about changing thermostat batteries and M21 means it is unable to update software.

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Google Nest thermostat code N1, N21, N71, N401 and the other low-power N codes: meaning and exact next steps

N1, N21, N71, N401 and the other low-power N codes means One wire is receiving power, but less than expected. Google names the wire for each code: N1, N21, N71 and N401 mean the Rc power wire is not connected to equipment; N2, N22, N72 and N402 mean the same for Rh; N3, N23, N73, N153 and N403 are W1; N4, N24, N74, N154 and N404 are Y1; N5, N25, N75 and N405 are W2/AUX; N6, N26, N76, N156 and N406 are G; N7, N27, N77 and N407 are O/B; N28, N78 and N408 are Y2; N29, N79, N159 and N409 are the star wire; N414 is no power to AQ+ on a one-wire accessory and N415 is an AQ- wire without an AQ+ wire.

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Google Nest thermostat code N262, N263, N412, N413: meaning and exact next steps

N262, N263, N412, N413 means In extremely cold weather only: no power to the Y1 wire is detected, the same cold-weather shutoff as the E10 group. N412 also appears on Google's list for a system that needs maintenance.

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Google Nest thermostat code N416, N417, N418, N419, N420, N421, N422, N423: meaning and exact next steps

N416, N417, N418, N419, N420, N421, N422, N423 means The thermostat detected an overvoltage or overcurrent error on the HVAC equipment. Google says the HVAC system may need maintenance.

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Google Nest thermostat code T01, T02, T03 and the other T codes: meaning and exact next steps

T01, T02, T03 and the other T codes means A system-test problem: the test after installation found that one part of the system did not respond. Google's list: T01 single-stage fan, T02 single-stage cooling, T03 two-stage cooling, T04 forced-air system, T05 radiant heating, T06 radiator heating, T07 baseboard electric heating, T08 humidifier, T09 dehumidifier, T11 two-stage fan, T12 three-stage fan.

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Google Nest thermostat code TD001, TD003, TH003 and the other TD and TH codes: meaning and exact next steps

TD001, TD003, TH003 and the other TD and TH codes means The thermostat has trouble connecting: TD001, TD005 to TD008, TD010 to TD012, TD014 to TD017 and TD019 to TD022 mean it is having problems connecting to Wi-Fi or the app (Google's article is for a thermostat that is offline); TD003, TD004, TD009, TD018, TD023, TD024, TD027, TD028 and TD030 occur while adding the thermostat to the app; TH codes (TH003, TH004, TH008 to TH011, TH013 to TH019 and TH026) cover Wi-Fi and Thread network setup problems.

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Google Nest thermostat code W3, W4: meaning and exact next steps

W3, W4 means The thermostat failed to connect. For W3, Google says the router is not giving the thermostat a network IP address. For W4, the thermostat is connected to the wireless network but not to the internet.

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Google Nest thermostat code W5: meaning and exact next steps

W5 means The thermostat cannot connect to Wi-Fi. Google says this can indicate a hardware malfunction, and the thermostat may need replacing.

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Every code

Every Google Nest thermostat code: what it means and what to do

Google Nest thermostat code E1, E297

The thermostat needs a common wire (C wire) or a Nest Power Connector because it is not getting steady enough power. Google words E1 as a common wire being required and E297 as a C wire or Y1 wire being required.

Turn off the system power at the breaker, pull the display off the base and check whether any wire is in the C connector.

Google's steps: if the C connector is empty, check whether the system has a spare wire you can use as a C wire, connect it to the C terminal on the system's board and to the thermostat's C connector, then press the display back on and restore power. If there is no spare wire, a professional has to run one or fit the Nest Power Connector. On E297 while installing the Nest Power Connector, Google says the thermostat needs a software update from Settings, then Software Update.

Google Nest thermostat code E11

A heat pump wire (O/B) is detected, but Google says no heat pump system is present.

Check whether the equipment is really a heat pump, and look at the wire in the thermostat's O/B connector.

Google's wiring steps: turn off power, pull the display and compare the wires with the setup wiring diagram. The diagram shows which connector each wire belongs in, so a wire in O/B that the diagram places elsewhere has to be moved.

Google Nest thermostat code E13, E33, E36, E37, E38, E83, E86, E87, E88, E413

Too many auxiliary heat wires are detected for a heat pump.

Photograph the thermostat wires and note how many auxiliary heat wires (W1, W2/AUX) are present with the heat pump wires.

Google's wiring steps: compare the wires with the setup wiring diagram and move any wire that is in the wrong connector. so the wires match what is really connected.

Google Nest thermostat code E260, E298, E448

The thermostat reports no power. Google words E260 as no power to Y1, and E298 and E448 as no system power.

Check the breaker and the system's power switch, and check that the furnace panels are on.

Google's "Troubleshoot power" steps: confirm system power is on, then with power off pull the display and check each wire is fully inserted and connected properly at the system board.

Google Nest thermostat code E299

Google's table lists E299 with a single instruction: contact support.

Write down the code and the thermostat's serial number, which is on the back of the display above the QR code.

Google gives no self-repair steps for E299. Contact Google Nest support with the code and serial number ready.

Google Nest thermostat code E35, E85

A dual-fuel system can have at most two alternate heat wires, and the thermostat detects more.

Count the alternate heat wires in the thermostat base.

Google's wiring steps: use the setup wiring diagram to find which wire is in the wrong connector, correct it and re-test.

Google Nest thermostat code E39, E89, E169, E269, E419

A Y2 wire is detected without a Y1 wire.

Look at the Y1 and Y2 connectors and check that a wire is not sitting in Y2 when it belongs in Y1.

Google's wiring steps: compare the connectors with the setup wiring diagram and move the wire to the right one. E269 and E419 are corrected through the Home-app wire configuration, which means resetting the thermostat and re-entering the wires.

Google Nest thermostat code E4, E24, E74

The thermostat detects no power to the Rh wire.

Check the system power switch and breaker, then look at the Rh connector on the thermostat base.

Google groups this with the other power codes and points to its "Troubleshoot power" steps: confirm system power is on, then check that each wire is fully inserted, its connector button is down, about 3/8 inch (6 mm) of bare wire is showing and the wire is connected properly at the system board. Google's hot-weather article lists E4, E24 and E74 with the E3 group as codes that can appear when a cooling system trips off in summer.

Google Nest thermostat code E40, E90, E420

A W3 wire is detected without a W2/AUX wire.

Look at the W2/AUX and W3 connectors and check for a wire in the wrong one.

Google's wiring steps: compare the connectors with the setup wiring diagram and move the wire to the right one.

Google Nest thermostat code E41, E91, E421

An E (emergency heat) wire is detected without an O/B wire.

Check the E and O/B connectors for a wire in the wrong place.

Google's wiring steps: compare the connectors with the setup wiring diagram and move the wire to the right one.

Google Nest thermostat code E5, E25, E75, E155, E255, E405

The thermostat detects no heating or cooling wire. Google says a W1 or Y1 wire is required.

Photograph the wires in the thermostat base and compare them with the wiring diagram the app gave you during setup.

Google's "Troubleshoot wiring" steps: confirm system power, turn power off, pull the display and check that each wire is in the connector the app's wiring diagram shows, fully inserted, with the button down. E255 and E405 come from the Home-app wiring configuration, where Google says to reset the thermostat to factory settings and add it back to the Home app, re-entering the wires from a picture of the old thermostat.

Google Nest thermostat code E6

Too many wires are detected. Google's message says to remove at least one of the O/B, W1, Y1 or AUX wires.

Look for more than one wire pushed into a single connector, and for a wire in the wrong connector.

Google's wiring steps: check that each connector holds only one wire and that every wire matches the setup wiring diagram, moving wires to the connectors the diagram shows. The message itself tells you the fix is to remove at least one of the four listed wires so the thermostat sees a valid combination.

Google Nest thermostat code E7, E27, E77, E407

The thermostat does not detect a Y1 wire, and Google says a heat pump requires one.

Check whether the system is a heat pump and whether a wire is in the thermostat's Y1 connector.

Google's wiring steps: with power off, pull the display, and make sure a wire is fully inserted in the Y1 connector with its button down and that the wires match the wiring diagram the app gave you during setup.

Google Nest thermostat code E9, E29, E79, E159

The thermostat detects no power to the C wire.

Check the system power switch and breaker, then check that the C wire is fully inserted at both the thermostat and the system board.

Google's "Troubleshoot power" steps: confirm power is on, turn it off, pull the display, check each wire is fully inserted with its button down and about 3/8 inch (6 mm) of bare wire, and check that the C wire is connected properly at the system board.

Google Nest thermostat code N260, N261, N410, N411

Google words N260 and N410 as a C wire or Nest Power Connector being recommended for the thermostat, and N261 and N411 as low power on the C wire.

Check whether a C wire is connected and fully inserted at both the thermostat and the system board.

Google's C-wire steps: check the thermostat's C connector for a wire that is fully in with its button down, look for a spare wire in the system that can serve as a C wire, or have a common wire or the Nest Power Connector installed. If you already installed the Power Connector, update the wiring in the app under Settings, Thermostat Wiring.

Google Nest thermostat code W1

The Nest thermostat cannot continue to connect to your Wi-Fi network. Google says the router may not fully support a Wi-Fi standard known as power saving mode.

Check Google's list of Wi-Fi routers that are incompatible with Nest products against your router's model.

Google's cause is a router that does not fully support power saving mode, so the fix is on the router side: look up your router on Google's incompatible-router list and follow its guidance.

Google Nest thermostat code W2

The thermostat failed to connect because the router may have security settings enabled that prevent it from connecting.

Look in the router's settings for MAC filtering or an access list.

Google's fix: find the thermostat's MAC address (Google has an article for locating it) and add it to the router's allowed devices, sometimes called a whitelist.

Google Nest Help — Troubleshoot Nest thermostat help codes; Google Nest Help — Troubleshoot thermostat power issues during hot weather (E3, E4, E23, E24, E73, E74, or E195 help codes)