Bought our 2018 A180d three weeks ago and we have had this issue intermittently. Today it was 21 degrees outside and for a half hour drive the car just pumped in warm/hot air unless climate control was set to LOW. Tried car short time after getting home and air con cooling came on immediately! Will go back to dealer hopefully to sort but as it is intermittent my hopes are not high! From reading other posts looks like could be control unit?