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Nest Gen 3 Learning Thermostat Install

Community Member

Hi! I just installed a gen 3 Nest Thermostat. The thermostat is powered on but it will turn on the heat or the fan. The old Honeywell thermostat had 3 wires - G, W, R.

Photos in order are: old thermostat wiring, old thermostat, wiring in furnace, nest thermostat wiring.

The furnace is a Bryant 915S.

I first tried without the C wire. The thermostat would power on, but it would not power the heat or the fan.

I had extra wires, so I wired the C wire, but still no heat or fan.

Troubleshooting codes: t01, t04

What am I missing?

Thanks for the help!


Community Member

This has been solved. 

Community Specialist
Community Specialist

Hi Dominick_,


Thanks for posting in the Google Nest Community forum. I'm glad to hear that everything resolves immediately. If you have questions or concerns, please feel free to let us know by creating a new thread, as we'll be willing to help.