You need a set of a/c gauges. They hook to the service ports on the system.

 

Possibly more info on jumping the low pressure switch? In have the same problem. But I noticed the AC compressor doesn't kick on at all.

Then... I checked the fuse box. No fuse!!!!!! So i put one in and...

Nothing (didn't blow fuse either)

 

First step is gauges, to see if there's even any refrigerant in it.

 

The pressure switch is on the accumulator tank. It's the round cylinder with the low pressure line going to it. It's a simple on/off pressure switch. Just disconnect the leads and short them to each other with a jumper. But Sean is right if there is no coolant then it won't help. Also the coolant contains lubricant so running the pump dry may damage it. AutoZone has professional high low gauges for $60. Harbor freight has them for around $30 when on sale. HF also has the vacuum pump to evacuate the system properly.

 

Agree with all above. At best, I'm a 5 on a scale from 1-10 on truck knowledge but do know one thing, RTFM and diagnose. That means "throw some guages on ".