help with wiring

[richey04]

In January I installed a Nest, to replace an old thermostat. Heat worked great, and I didn't think to check the cooling since I live in the Northeast. A recent 90 degree day prompted me to turn on my air conditioning, but no cooling mode appears in the Google Home app or on the Nest device itself. I do have AC, it worked with the old thermostat. But I only have 4 wires (red, blue, white, and green), no yellow wire. During the winter months, when heat and fan worked flawlessly controlled by the Nest, red was connected to R, blue to C, white to W, and green to G. Unfortunately, I don't have the old thermostat. I threw it out. Thanks in advance for the help.

[Candi]

I’m having the same issue. Hopefully someone responds soon!

[Patrick_Caezza]

Post a picture of the original thermostat's wiring

[MelbaDT]

Hey folks, 

Thanks again for lending a hand here, Patrick_Caezza and mikev552. 

richey04 and Candi, have you seen Patricks's response above? If you still need help with your thermostats, please provide the requested photos so we could check on them further. 

Best, 

Melba

[MelbaDT]

Hey there, 

Checking back in — how's it going with your Nest thermostat devices? Let us know if you still need our help. 

Best, 

Melba

[MelbaDT]

Hi, 

We haven't heard from you in a while so we'll be locking this thread if there is no update within the day. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the community.

Best, 

Melba

[mikev552]

Hello, sound like you don't have a wire connected to Y which is cooling/AC. Post a pic if you can of wiring..I just installed a Nest and I did a rewire so I now have 5 wires on a forced air heat/AC. You should have at least 5 terminals connected. Y C W G R should all be connected if you have heat and ac system...

[mikev552]

 you should have something like this....C should be used as it supplies constant power to Nest....It all depends how you are wired from the furnace control board and running to the thermostat

[Patrick_Caezza]

Do you have a picture of the original thermostat's wiring? If yes, post it here.

If you don't then post a picture of the terminal block on the control board.