My airflow control is crazy!...

[RAW]

random question...my airflow control knob on my dash (94 FD) does the opposite of what it says.  when it\'s on windscreen, it blows air from the vents and vice versa.  you cant just take the knob off and move it as it only goes on one way.
 
anyone got any ideas how to return it to normal!? :3Confused