hot air flow problem

[ColinR32]

Hi all, hope someone can help?

i have a 2005 audi a8 3.0tdi

so all of a sudden i am only getting warm air out certain vents in the car, cant ever seem to get wamr air going upwards towards the windscreen and only comes out of outer facing vents "not out centre two"

anyone any idea where i should start?

P.s i do have Full genuine VCDS also in case thats something i need to solve the issue.

Thanks colin