topic HVAC Whole Home Scent Diffuser- Script Editior in Smart Home Developer Forum

HVAC Whole Home Scent Diffuser- Script Editior

azmavhockey3 — Fri, 03 Oct 2025 19:53:00 GMT

Hello,

I was successful at Automating my SmartSwitch to turn on when the AC Kicks on and off (Attached). I wish to automate for the "Fan- Only" setting on my NEST thermostat.

Im getting an error [fan-only] is an invalid enum string. The list of valid enums: [on, off, heat, cool, heatcool]. When i check the Nest Developer page it states that "Fan-Only" should be a command. Any help would be appreciated.

https://developers.home.google.com/cloud-to-cloud/traits/temperaturesetting

metadata:
name: Lights ON when Fan-Only runs
description: If the thermostat is actively in fan-only mode, turn ON SmartSwitch
automations:
- starters:
- type: device.state.TemperatureSetting
device: Hallway - Hallway
state: activeThermostatMode
is: fan-only
actions:
- type: device.command.OnOff
devices:
- SmartSwitch
on: true
[fan-only] is an invalid enum string. The list of valid enums: [on, off, heat, cool, heatcool]

To turn on smart switch when AC kicks on:

metadata:
name: Scent diffuser ON when AC is cooling
description: If the thermostat is actively cooling, turn ON SmartSwitch
automations:
- starters:
- type: device.state.TemperatureSetting
device: Hallway - Hallway
state: activeThermostatMode
is: cool
actions:
- type: device.command.OnOff # Turn the device on or off.
devices:
- SmartSwitch
on: true

To Turn off With AC off:

metadata:
name: Scent OFF when AC stops
description: When cooling ends (idle), turn OFF SmartSwitch.
automations:
- starters:
- type: device.state.TemperatureSetting
device: Hallway - Hallway
state: activeThermostatMode
isNot: cool
actions:
- type: device.command.OnOff
devices:
- SmartSwitch
on: false

Re: HVAC Whole Home Scent Diffuser- Script Editior

Suc_dpe — Mon, 06 Oct 2025 17:50:53 GMT

Hello,

The issue is that "fan-only" isn't a valid value for the activeThermostatMode state in Google Home automations.

According to the documentation you linked, the valid values for activeThermostatMode are:

on
off
heat
cool
heatcool

"Fan-only" is a thermostat mode that exists on the device itself, but it's not exposed as a triggerable state in the Google Home automation system.

Workaround options:

Use a different automation trigger: Instead of triggering on the thermostat mode, create a schedule-based automation or use a manual trigger
Check if your thermostat exposes fan state separately: Some thermostats have a separate fan control trait. Check if your Nest thermostat shows fan status as a separate device state you could trigger on

Unfortunately, this is a limitation of the current Google Home automation system - not all thermostat modes are available as automation triggers. Your automation syntax is correct; the platform just doesn't support that particular mode value.

Re: HVAC Whole Home Scent Diffuser- Script Editior

jameskarl908 — Tue, 14 Oct 2025 15:52:05 GMT

Thank you, your post solved my hvac problem too

Re: HVAC Whole Home Scent Diffuser- Script Editior

Developer12 — Thu, 09 Apr 2026 12:50:28 GMT

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