sloppy/floppy dash vents

[ff6849]

My A/C dash vents just flop close when I try to use the my A/C any tricks to make them stay in place when you try to adjust the air flow direction........... After 40+years they have seemed to lost their desire to fight any air current 

[72cudamaan]

My A/C dash vents just flop close when I try to use the my A/C any tricks to make them stay in place when you try to adjust the air flow direction........... After 40+years they have seemed to lost their desire to fight any air current

There is a little tension clip on the pivot pin on the left side of each vent. It probably broke, but visual confirmation
is best. Not sure where to get a replacement other then maybe another vent from the junk yard.