When the AC is set to Max, most of the cold air comes out at your foot. Likewise, when you direct the air to the windshield, most of the air is discharged down below. Are there any simple tests to determine the cause?
Airflow is directed by flaps in the HVAC system. The flaps are vacuum controlled on some cars and electrically controlled on others. If you Regal has vacuum operated flaps, a vacuum leak, loose hose, or damaged hose can cause the problem. If it’s electrically operated the motor that moves the flap may be faulty.
It’s also possible that something is physically blocking the air flow flap, preventing it from moving.
Problems with the heating and AC system are best dealt with by an independent shop specializing in this sort of work. They have all the necessary equipment and knowledge to correctly diagnose and repair automotive HVAC systems.
The flaps are controlled by vacuum but I do not believe vacuum is being delivered to the switch. Do you know what produces the vacuum?