Hi. My English is not so good, but I'll try.
On my Polo 6n2 is not working the air selector, air comes from every holes even if I change from direct, or down, or windscreen. Someone could please tell me how to open to see what happened or have an idea how to fix? Thank so much!
All depends on the type of the Air conditioning you have (none, simple, climatronic)
There should never be a situation when the air can go all 3 ways at once, if that's the case, your direction flap inside the unit would have to be dismounted or totally mangled (not really possible to do)
if your Air box is manual, then either the linkadge is broken, or the knobs themself, possible to fix by yourself.
If you have an automatic air condition, then (unless it's just a fuse) most likely the flap motors are fried, or your aircon unit is, or your wiring harness is. Unless you know what you're doing, don't try to fix by yourself.