Car Climate Control UI

Why, when I change the temperature on the thermostat of my Renault Zoe does it change the fan direction, too? Is this a UI affordance for people who want their faces colder but their feet warmer? I don’t understand!

A white hand turns the thermostat knob in a car from 19℃ to 20℃ in 0.5℃ increments; the untouched nearby fan direction control seems to change of its own accord. Initially blowing towards the user's face it switches on 'towards feet' at 19.5℃ and switches off 'towards face' at 20℃, and reverses the process when the temperature is turned down again.

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