So I've looked through many posts all over reddit and other websites but it seems every furnace is slightly different.

I am an early twenties guy who doesn't want to burn down his apartment.

If anyone can help me wire up my new thermostat I would appreciate it.

I attached an album showing all the diagrams on the furnace/ac which I believe is gas furnace and electric air??

People talk about switching G for C but I don't have a C connection on the furnace?

Overall this has been a very frustrating experience so I thought it best to just ask people with experience wiring them.

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  • Where does the cable connected to Rc and Y go? Something's amiss here, because a normal gas furnace needs to know when the air conditioner's on in order to run the fan properly... Apr 11, 2018 at 22:32
  • Would be a good idea to mention the make and model of the thermostat and furnace
    – Stavr00
    Apr 12, 2018 at 17:43
  • Don't switch G for C that makes no sense, Your fan on uses the Green wire whether that's to your furnace or AC unit it don't matter, R takes in a red wire from your furnace and sends it out on W which is a white wire going out, RC takes is a red wire from the AC unit and sends it out on Y if you don't have a transformer in your AC unit then jump R to RC, then C is your common wire that's black, it's for LCD smart thermostats that don't require batteries, C just comes from the low voltage side on the transformer to provide direct power
    – user70085
    Nov 17, 2018 at 12:19
  • Did you ever get this resolved? If so, please give a check-mark to the answer that helped you the most, or write up your own answer explaining what you did to get it fixed and give yourself a check mark. That will help others with this kind of problem know that this has a resolution and is a good place to look for their answer.
    – FreeMan
    Aug 17, 2020 at 11:28
  • 3
    I’m voting to close this question because it's been abandoned.
    – FreeMan
    Dec 15, 2020 at 13:18

2 Answers 2


If you follow 24V VAC TRAN there are two thick wires SEC 1 SEC 2 that lead to the R (first from the bottom) and COM 24V = C (4th from the bottom) connections.


You would hook up the common terminal on the thermostat to COM/24V on your circuit board

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