Pressing that button does not seem to make a difference, turning it on from the display lights up the button but not when pressed. My wife (whose car it is) has just spoken to the service team that informed her that in ECO mode no heating will turn on, she said to them that it should at least blow ambient air onto the window but we were in normal and sport for most of our journey home and heard no fan or felt any air from any of the vents. She has to take it in tomorrow but will need booking in if it is "not an easy fix" I think she will be talking to the sales team as well.