RDeboys

Hi I'm having similar problems with my Audi A3 1.6 2015 heater with it blowing cold air. However both pipes to and from the matrix are hot and when I have the blower on at a very very low speed I get hot air our of the vents. As soon as I turn up the blower speed the heat disappears and the vents blow cold. Does anyone have any ideas or advice? Many thanks