GMC Repair: 99 suburban AC issues, friend move, good travel

Question
I have a 99 Suburban 1500 5.7l and the ac is fully charged it blows cold air but will not transition from floor to any other spot in the front cab, it trys to switch but ends up blowing back on the floor only. where do I even start? Is there diagrams available to help?

Answer
Hi
Sounds like the mode door actuator is your fault.
It is located above the gas pedal on the HVAC case.
It will have 2 "rods" attached to it and it moves 2 different doors in the case.
You should be able to lie on your back and look up and see it.
Have a helper/friend move the switch to change airflow, and you watch the actuator and doors. They should move freely and have good travel distance.
If not there is your problem.
The ONLY other thing it could be would be the controller.
I hope this helps.
Good luck
Pawl