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Nest Thermostat unable to start ventilator and furnace correctly; missing C wire

Community Member



My furnace was not able to start the ventilator and furnace correctly. It successively tried to start the ventilator, would falter and try again successively in quite a number of times before succeeding to start properly. 

The correction to this problem, was to have a wire connected to the «C» (Common) connection on the thermostat from the furnace. Once the C wire was connected, the problem was solved. If you want some more explanations on this problem, see the explantations on YouTube for this (try looking up «Nest Thermostat missing C wire»). 


Good luck


Community Specialist
Community Specialist

Hi gilleslibre,


Thank you for posting here and we appreciate you sharing it to the Google Nest community.


Nest thermostats are designed to use a very small amount of power, and in many cases they can use your system’s heating and cooling wires to get enough consistent power. Sometimes, you may need to connect a common wire (C wire) or power accessory, like the Nest Power Connector, to make your system compatible and to prevent some issues like heating or cooling not working.


If you have any other questions, don't hesitate to post it here.




Thank you for the support. 

Community Specialist
Community Specialist

Hey gilleslibre,


Thanks for being here in the Google Nest Community.


I'll go ahead and lock this thread and if you have any other questions or feedback, you can get back to us by creating a new thread.


Best regards,