since its getting colder out now i used my defogger for the first time in a while...the compressor clicks on and off and im not sure why, also my voltage meter rises up and down and it actually pulled enough juice where it shut the truck off...whats causing this massive power drain??? im pretty sure its low on refrigerant..but whats cause the power drain?

 

The A/C compressor cycles because it's drying the air for the defroster.
With the A/C being low that could cause the engine to rev lower than normal when the A/C cycles. Possibly a bad A/C clutch as well.
More people will chime in about the volt issue.

 

Yup low refridgerant will make it click on and off alot.

I would be testing output if the alternator first. It should be able to power the fan and defrosters no sweat. Use a voltmeter to see what its putting out. Should be 14.3-14.5 at the output leads.