I don't think it would open/close according to temperature. When heating the car, the "front cooler" works as an evaporator, getting cold but trying to stay as close to the outside temp as possible (=as "warm" as possible). When cooling, it works like a hot condenser and tries to stay as cool as possible. So it always wants to get a lot of airflow to stay close to outside temps. I think it only closes depending on speed, to get better aerodynamics. So when there is much more the enough airflow cause you drive fast enough, I think it will gradually close and open up again when driving slower/stopping.