On a cold day (say 3 deg C) and on a long run (at least an hour), with the climate control set at 20 deg C , very cold air is suddenly blown into the passenger footwell. The first time this happened it would not stop, even after a short break and with the climate turned up to 29 deg C. The car is now just one year old and when I returned it to the dealer for investigation it behaved perfectly. Anyone got any ideas?