Recent problem on blower fan for a/c:

My center dash vents do not blow any air. In all settings, air flows through top defroster vents and side vents. Nothing can change this, no matter what setting.

Fan speed buttons oeprate fine.
Can switch from a/c to just economy without any problem.
Is this a vacuumm hose thing or a fuse?
But man, with summer coming, would love to have air flow back through the center vents.

any ideas?

Thanks!!