Stuck airvent louver/directional knob

I’m writing about the knob on the dash that directs the air between defrost, face, feet, or some combo. It should twist clockwise all the way from 7 o’clock past noon to about 5 o’clock, and back again.

When it was working, if I chose 7 o’clock, all the air (hot, cold, vent) is directed at my feet. If I choose noon the air is towards my face, and all the way over to 5 it’s defrost only.

I can move the knob as I need to between 5 o’clock and 12 o’clock (the defrost and upper-level stuff), but for several months now I haven’t been able to move the knob past 12 o’clock towards 7 o’clock. It feels physically stuck, and I can’t force it.

There are a few degrees of bounce right at 12 o’clock, which is partly what makes me feel there’s a physical blockage back there. Between noon and 5 it twists fine and I get what I ask for.

When it worked correctly, I could feel / hear it flip from face to face/feet when I moved the dial. I thought what I was hearing was the louvers being reset.

I’m wondering if there’s something physical blocking the mechanism behind the dashboard, or if perhaps a connection has been broken back there. Maybe it’s not the knob that’s broken: perhaps the louver itself is stuck in “face” position.

Could a pencil or something have fallen from the dashboard near where it meets the windshield? I can’t get my hand in there.

The air itself works fine, I just can’t choose any of the “air from floor” selections, either mixed with “air to face” or on its own.

Spouse tells me that taking the dashboard off is $$ and not for amateurs. I’m doing regular maintenance but the air filter probably needs changing: could someone have bumped this lever when changing air filter before? The knob has been stuck for a while, since winter, but the annoyance factor has increased since the weather’s gotten warmer.

Thank you!