2010 F150 Defrost Only
 

I have a 2010 F150 XLT which is only blowing cold/hot air through defrost. There was clicking noise coming from behind radio. I figured this was the blend door actuator. I replaced the actuator, no ticking; but still only have air coming through defrost.
I have read several posts regarding vacuum lines may be causing this. Only thing I have found though have been older model F150's.
Any suggestions on where to begin my next leg of finding the problems. I really do not want to take to dealership. I was told to replace the actuator would be around $1000.00. There was a simpler way to replace it than remove the dash.
Thank you in advance for any help which can be offered. I still have cold air; but not from dash vents.

Does your vehicle have the Manual or Automatic Climate control set up?

Manual control

Usually when only defrost function is operating it generally means there is a good size vacuum leak in the line that comes from the engine to the inside of the vehicle. The system is designed such that when a failure/malfunction occurs the system will default to defrost mode , can be a safety item.
Look for the thin line that comes to the inside in the engine compartment. Sometimes they become brittle and crack or break altogether. It could also be off the function selector on the dash , not very common.