over heating
 

hey yall, quick question. i was puttin new seat covers in my truck the other day in the drive way and had the truck runnin with the ac goin cause it was hot and about the time i go to shut my truck off i noticed it was steamin and boilin over and i was like wtf and let it cool down and put water in it and drove it and it was fine didnt get hot at all and yesterday i was feedin the horses and left it runnin with the ac on and it just died and started steamin again and wouldnt start untill it cooled down, so why does it overheat like that when its just sittin, i would think that i could leave it runnin and it be fine, or am i wrong?

Not enough air going through the radiator.