99lariat4x4

just got this truck jan 6 for xmas from my mom.. im learning to be a technician sorta, and i notice that my compressor NEVER turns off. the clutch isnt stuck, i unplugged the high pressure switch wich should turn the compressor off , but it still runs, so i figure its a short, but i would think there would be a fuse blown, but i cant find anything. i was just wondering if this mighta been a common problem. or maybe im just over looking something. just lookin for a little help.