Okay, thanks Wiggy. So it's heat of the engine and not the heater? As I say turning the heater down cools the flow from the vents, this is when it's turned offIf you mean when you are moving then yes, it's normal.
Air is forced through the vents in the scuttle and down the tubes into the car with the forward motion of the car.
Same thing happens in the van i drive, to stop it simply close the air vents.