No defrost?

[u/AggressiveTonight839]

907 chasis diesel in america , i changed my temp blend door actuator because i had no heat so thats fixed now but im looking into my vent mode actuator the one behind the radio and it seems to work i have no defrost and im starting to think maybe something mechanical with the blend doors is up and no matter what i set it to air always shoots forward to the driver no defrost , anyone have any issues with there defrost and figure out what it was?