My AC has been working fine recently, although not COLD air, but cool enough for the 80 degree temps lately. Today, I take off and turn on the A/C and I have nothing but warm air, this is a dramatic difference in temp from the cool air I got just yesterday. I turn the A/C on and off a few times and realize I dont hear the compressor turning on or changing the idle of the truck. So here I am with FSM in hand, I have checked the tension in the belt to the compressor and its seems fine. Next thing to check seems to be the magnetic clutch .... what is this? I cant find it in the diagrams in the FSM? It's also saying I should be checking for abnormal noise .... what would this sound like? I know next to nothing about the A/C system, but am assuming the compressor pulley should be spinning all the time and this magnetic clutch would engage when I hit the button in the cab and the idle would change and I should have AC. Are there any easy and obvious things to check before I start really digging into it? Any help is greatly appreciated ..... THANKS!!