Cold air blowing at feet but warm at all other vents

[Rodney79]

Can anyone help - my A4 Avant 2016 is blowing cold air in footwells but warm through all other vents! surly it cant be the heater matrix as this would have cold air in all vents? Any suggestions? 

Thanks 

[matty_s6]

The only thing I have had similar was that the cooling system was blocked on a 2017 passat, it ended up being the silika bag in the coolant bottle had burst, it blocked the matrix and the cooling system.