Upper vent won't adjust

One of the thing I love about my BMW is the setting that allows heat on your feet and cool air from the dash onto your face.
However, the temp of the air coming in up top can no longer be changed-- the thumb wheel moves up or down as always, but the air stays warm. Summer is coming, and I need that cool air . I hate warm air on my face any season.
Would this be an easy repair? Do I need to somehow remove the dash?

We have VERY limited car fixing experience, but I am worried that if we go to a dealer it will cost a lot!

Thanks for any help

Ellen

tyr adjusting the flow fo cold air somewhere else. If no cold air blosw out, period, from any vent, your compressor may be on its way out (bad java), or you may just need to recharge the system (a kit from Pep Boys or Autozone for cheap).