Jeep Repair: jeep a/c, jeep grand cherokee, grand cherokee

Question
i have a 03 jeep grand cherokee when you turn on the a/c it may blow cold air but then it will start blowing half way cool air and it will also blow on the windsheild then your feet then it will blow out the vents in to your face without me turning the selector knob. it will also do this sometimes on the heat.  please help it is driving me crazy

Answer
More than likely you have a blend door going bad.  The blend door opens and shuts to to mix the cool and hot air.  You could also have a bad head unit (where the selector knob is).  This one is hard to diagnose, you may want to get it checked professionally.  Hope I could help!