my a/c blows cold for a few min. but will blow hot when idling for more than a minute and the engine temp guage goes to hot. as soon as i get on the hwy the guage returns to normal and air is cold again. is this an a/c clutch problem and if so i've found info on this site on how to set the air gap but it was for a 00 sdd. is it the same for an 08?