03-08-2026 09:05 AM
Hello,
I just moved into a new apartment and set up my account on a Nest thermostat that had been working previously. Its a heat/cool system, and it uses a forced air gas heat system. The wiring setup has Y W G R.
My problem: when the heat turns on, I hear the gas flames turn on, but when the fan is supposed to come on, instead the gas turns off. It tries this three times and then stops altogether.
when I turn the mode from heat to off, I can then turn on the fan manually. But in heat mode the fan does not come on.
ive attempted many resets, both “activate” and “don’t activate” for the fan during heating, and not sure what else to try.
one potential factor: I initially installed the nest app before the google home app. I just tried deleting the nest app, but still having the same issue.
any help appreciated!
03-09-2026 11:43 PM
@AJ34 ,
Most gas furnaces have an Integrated Furnace Control-board. The furnace heat exchanger must reach 250°F before it turns on the blower fan.
Can you get me the manufacturer and model number of your gas furnace?
The Cooling Wizard