Air condition only blows cold air with max air on. Fan blows air fine

What is your question?

Fan blows fine. When i turn on air it blows normal and strong but only hot air. When i then turn on max air it gets as cold as it should. I figure since it gets cold on max, freon is okay??? Fan blows strong and in all vents , so i feel its not a blower/flap door issue. Truck only has 43ooo on it. Ideas?? Could it be dash switch or fuse??