Hello and welcome to JustAnswer!
If the control head has already been replaced then that leaves the mode door itself, the mode door actuator, and the wiring in between the control head and actuator. The mode door is the door in the heater box that controls the direction of airflow, the actuator is the electric motor that controls it.
The next thing I would do is remove the actuator and see if the door is broken, and see if it will turn by hand if it isn't broken. If it will move by hand and direct airflow then I would recommend replacing the actuator, if it won't turn by hand or is broken then the heater box will need to be disassembled to replace the door.
Thank you. I will follow up on the recomendations for repairing my 2005 Ford Freestar that has heater/ac airflow problems. I will have my Ford mech. take a look at it. The solution does seem probable. James Farmer