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2 Wires Sharing Aux/E

Community Member

I am concerned that I did this correctly?  I installed 2 thermostats and it was late so I rushed on this last and final 3rd one.  I have 2 wires (black/white) sharing the Aux/E port. (The other 2 did not have this set up).  I was stumped so I googled it and with no research went with the 1st thing that popped up.  Someone somewhere said the white was the aux so and the black wire in W2 Aux.  Sounded legit so I went with it!

Went through the setup and the A/C works!  But I am concerned when winter hits?  Will I fry my system when the heat turns on?  Will I have issues?  I am either really lucky that it works or I am stupid and should of called a pro (I am confident both are true!).  My DIY attitude is try it yourself and when you get stuck or mess it up call a pro!  I am 60/40 on calling pros and doing it myself.  Or maybe 40/60 I can't remember!😂  I am cheap and I don't want to call a pro!  Help!






Community Specialist
Community Specialist

Hi BigEdAssassin,


Thanks for posting in the Google Nest Community forum. I'd like to take a closer look at it. Could you please take a photo of the wires connected to your system's control board? It will help us to ensure the use of your black and white wire. Please make sure that the labels of the wires are visible. 


For more information, you can visit this link to install your Nest Thermostat