When calling the service climate.set_fan_mode to my Nest thermostat with the new API with ‘on’ as the mode, the fan is only turned on for 15 minutes as that is the default for the thermostat. I am not sure if this is a bug, or would need to be a feature request, but setting the fan mode to on should keep the hvac fan on until turned off, and maybe a new mode “timer” could be added with an additional parameter for how long to run the fan for.