Turn on the Nest in fan-only mode when it's too hot in the living room.

nest_fan_cooler.sh

#!/bin/bash

API_KEY='Authorization: Bearer API_KEY_RETRIEVED_USING_PIN_CODE'
API_URL='https://developer-api.nest.com'

TS_ID='curl_/devices_to_get_this_hash'
TS="devices/thermostats/${TS_ID}"

MIN_TEMP=70
THRESHOLD=2

api_curl() {
    curl -L -H "${API_KEY}" "$@"
}

get() {
    api_curl -X GET "${API_URL}/$1"
}

put() {
    api_curl -X PUT -d "$2" "${API_URL}/$1"
}

give_up() {
    echo "$@"
    exit 1
}

current=( $(get "$TS" | jq -r '. | "\(.is_online) \(.fan_timer_active) \(.hvac_state) \(.ambient_temperature_f) \(.target_temperature_f) \(.device_id)"') )
#current=( $(cat nest_api.thermo | jq -r '. | "\(.is_online) \(.fan_timer_active) \(.hvac_state) \(.ambient_temperature_f) \(.target_temperature_f) \(.device_id)"') )

if [[ $TS_ID != "${current[$((${#current[*]}-1))]}" ]]; then
    give_up "API output did not contain a valid device_id"
fi

if [[ ${current[0]} != "true" ]]; then
    give_up "Thermostat is not online"
fi

if [[ ${current[1]} != "false" ]]; then
    give_up "Fan is not stopped"
fi

if [[ ${current[2]} != "off" ]]; then
    give_up "Heater is not off"
fi

if [[ ${current[4]} -lt $MIN_TEMP ]]; then
    give_up "Target temperature ${current[5]} is below $MIN_TEMP F"
fi

if [[ ${current[4]} -ge ${current[3]} ]]; then
    give_up "Current temperature ${current[3]} F is not more than target temperature ${current[4]} F"
fi

if (( ${current[3]} - ${current[4]} < $THRESHOLD )); then
    give_up "Current temperature ${current[3]} F is not $THRESHOLD F more than target temperature ${current[4]} F"
fi

echo "Turning on fan, current ${current[3]} F versus target ${current[4]} F"
put "$TS" '{"fan_timer_active":true}'

I don't have an AC, but I have a plain heater, and it has a fan-only wire, so I ran that to the Nest. Unfortunately, the Nest doesn't currently understand that I want it to run the fan when the temperature exceeds a threshold, to redistribute that heat throughout the house, so this script does that.

To use this, you need to sign up for a Nest Developer account. They're free for individuals and as long as you only use this on your own thermostat, you don't have to do any sort of approval process.