CHEVROLET SILVERADO DEFROSTER STUCK

My Truck Will Not Switch From De­frost. Do I Need To Re­place The Ac­tu­a­tor? If So, Where Is It And What Is The Part Num­ber?

I Have Re­placed The Mode Door Ac­tu­a­tor, And I Also Re­placed The Con­trol Unit. Every­thing Has Power And Is Work­ing Like It Sup­posed To But...

When I Switch To Have Air At The Dash Vent, Noth­ing Comes Out. It Seems To Be Stuck On De­frost And Feet. The Fan Is Work­ing Just Fine Along...