OK, when I have the A/C on fresh it blows good, but on Max you can hear the blower, but weak out vents. Where would the diverter door be. On a 1999 f-250.

 

Check the floor/intake area for an obstruction first.

 

Yep. The door is up behind the glovebox. Sounds like it might have sucked in a plastic wrapper or bag.

 

Hey thanks for the ideas, I have looked behind the glove box, and I see one vacum lever that moves, I'll check for a bag.

 

Any updates on this?

I have same issue, but no clogs or bags obstructing intake.

On normal A/C it seems to blow fine, but when switched to max A/C, the airflow decreases slightly but you can hear the blower working harder.

 

The blower isn't actually working harder, it's just that you can hear it better when the diverter door is open to the cab instead of the cowl vent.