2004 Dodge Truck AC

Air Conditioning problem
2004 Dodge Truck Two Wheel Drive Manual 162000 miles

hello when I get in my truck an turn on ac sometimes it comes on I will be driving an it quits blowing sometimes iwill be driving an then it comes on. I can get in an push my ac button an the button lights up but nothing happens an sometimes it works I will have windows down an iwill feel cool air comingi out vents an roll up windows an it stops blowing roll windows back down u can feel cool air blowing again not very strong whats happening