Google Nest

2 field manuals · 34 error codes · 3 guides

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Thermostat

Google Nest thermostats

Field manual · Thermostat

Google Nest Learning Thermostat (3rd and 4th gen): quick sheet

Nest Learning Thermostat 3rd generation and 4th generation (released 2024). 24 V systems only.

4 components2 common failuresGoogle Nest

Field manual · Thermostat

Smart thermostat installation & troubleshooting: field service manual

Wi-Fi thermostats for 24 VAC systems: Nest Learning/Nest Thermostat, ecobee, Honeywell Home T-series/Lyric, Sensi, Amazon Smart Thermostat. Line-voltage models (e.g. for baseboard heat) are covered only by the safety notes.

3 components5 common failuresGoogle Nest, ecobee, Honeywell Home / Resideo, Emerson Sensi, Amazon

Error codes

E1 C wire requiredE2 / E22 / E72 / E402 No power wire detectedE3 / E23 No power on the Rc wireE4 No power on the Rh wireE5 / E25 / E75 / E155 / E255 / E405 No heating or cooling wire detec…E6 Too many wiresE7 / E27 / E77 / E407 Y1 missing on a heat pumpE9 / E29 / E79 / E159 No power on the C wireE10 / E30 / E66 / E80 / E116 / E160 / E196 Lost power through the Y1 (cooli…E11 O/B wire without a heat pumpE12 / E32 / E82 / E162 No power on the W1 (heat) wireE24 No power on the Rh wireE52 / E102 / E182 Overcurrent on W1E53 / E103 / E183 Overcurrent on Y1E54 / E104 / E184 Overcurrent on G (fan)E55 / E105 Overcurrent on O/BE56 / E106 Overcurrent on W2/AUXE57 / E107 Overcurrent on Y2E58 / E108 / E188 Overcurrent on the star (*) term…E73 No power on the Rc wireE74 No power on the Rh wireE195 No power on the R wireE297 C or Y1 requiredE298 / E448 No system powerN254 No power on Y1N260 / N410 C wire or Power Connector recomm…N261 / N411 Low power on the C wireN262 / N263 / N412 / N413 / E296 Low power or low battery (Y-wire…N416-N423 Overvoltage or overcurrent on HV…W1 Wi-Fi drops repeatedlyW2 Wi-Fi connection refusedW3 No IP address from routerW4 Wi-Fi OK, no internetW5 Cannot connect to Wi-Fi (possibl…

Guide · Thermostat

Smart thermostat offline / Wi-Fi problems

Separate network problems (router, credentials, internet) from power problems: many smart thermostats switch the radio off when batteries or borrowed power run low. Read the brand's code first.

5 steps ~30 mineasy

Guide · Thermostat

Installing a C-wire adapter (Nest Power Connector, ecobee PEK and similar)

An adapter mounts at the furnace/air-handler board and lets the existing wires carry both the calls and constant 24 V. Check compatibility first: dual-transformer, fan-coil and communicating systems are commonly excluded.

5 steps ~45 minmoderate

Official Google Nest manuals & support

Brand names identify appliances only. OnCall Tech is not affiliated with or endorsed by Google Nest.