Hey I got a 98 4.6, the ac will blow good and cold until you hear something thump under dash usually after you give it has in gear then instant hot air out vents. Pop the hood ac clutch is engaged low pressure line is cold and has condensation on it. I know the blend door is messed up BUT I have it manually swapped over too where it blows cold. Know this is gonna get questioned so I can tell you I rigged it, cut a hole in box and have it where I can swap it until I have time too pull dash. I need too know what else this could be.

 

Nothing. It's the busted blend door.