I've noticed over the last few months that when I switch the MODE on the a/c & heater from all dash vents to bi-level or floor it either doesn't switch them at all to the floor, or only rarely does - the last setting for defroster/floor will blow on the windshield.

I know there is a mechanism that adjusts this (is it called a mixer? can't remember...) - anyone have similar issues / suggestions for a fix? I did some searches but didn't turn up anything...it would be helpful to know what to search for, however!

Thanks in advance...