a/c question
 

so i had my a/c working fine on a 96 3.8l i just got. the check engine light kept comming on and i found a vacum hose busted. it was not a thick rubber vacum hose that they sell at the parts store though it had a fat connector which went down to a super small line going to another fat connector that plugged into a small three prong setup in the back corner of the driver side under the hood. of course the parts store gave me some fat hose that would fit the connectors but inner tubing is super huge compared to the original. my a/c compressor is not turning on now. is this a coincidence or does the vacum hose have something to do with it? and if one has nothing to do with the other should i go pull that hose off a car at the salvage so i have that small tube, or does the size of the tube really matter?

so i got ahold of a gauge and no pressure. leak! what is the best way to determine the leak, i see freon with uv leak detection, anyone used this? also how many cans should you do if you are filling up an empty system? cans go up or down during filling? i think valve up is suppose to be gas and valve down is supposed to be oil i think is what i've heard but how much do you need of each and how do you decide?