Solved: Newly installed Google Nest thermostat (Gen 3) cycling the fan on/off continuously

Mike651 — Thu, 21 Mar 2024 16:36:00 GMT

I have just installed a new gen 3 nest thermostat and it cycles the fan on (100 sec) / off (1 sec) when the heat is off or above setpoint. My old thermostat was connected to W, G and R (jumpered to Rc). I have connected G, W1 and Rh on the nest and have tried G, W1 and Rc which returned a "no power" error.

the fan will run continuously when asked while in heat mode with the setpoint well below actual. I cannot shut the fan off without turning off the power to the furnace.

the nest appears to be working properly beyond the fan cycling issue.

I am running a gas furnace with logic that keeps the fan on for 100 seconds after the setpoint is reached and the burners shut off. there is no A/C but the unit was able to run the fan independently with the old controller.

Moderator edit: Subject updated for clarity and findability.

Re: newly installed Google Nest thermostat (Gen 3) cycling the fan on/off continuously

Mike651 — Wed, 28 Feb 2024 19:47:21 GMT

google nest assist suggested adding a connection to the nest "C" port from the furnace's "B" terminal (as there is no "C"). It worked!!

topic Solved: Newly installed Google Nest thermostat (Gen 3) cycling the fan on/off continuously in Nest Thermostats

Solved: Newly installed Google Nest thermostat (Gen 3) cycling the fan on/off continuously

Re: newly installed Google Nest thermostat (Gen 3) cycling the fan on/off continuously