Need some help troubleshooter my heater

[coggonobrien]

Hi guys,

I have no/very little air moving the air ducts of my 69 blazer k5 custom. it is a non-air truck with the 3 lever and toggle switch hvac controls. when i turn the key on i can hear the motor moving (albeit it is very quiet with the hood opener and no top on the blazer. Also the 2 top levers (defrost and air) are broke off/missing and have been since before i got the blazer.
What's your thoughts?

Thanks,
David