I have a 1993 Ford f150 4x4 strait 6 with around 200 thousand miles.The air conditoning works fine in normal but when you turn it to max it shuts off within 60 sec.You have to turn it to off poss then back to normal to get it to work.I live in a small town and I have gotten 3 diff. diagnosis.I would like to have an idea whats wrong before I have someone fix it,or if its something simple fix it myself.Thanks,Robert