2002 buick lesabre a/c works occasionally

Try buying a A/C recharge and put in the vehicle if the pressure weakens the a/c will feel warm. Older vehicle tend to start leaking after years of faithful service, Check for leaks with a Black light (you have up in the attic next to the lava lamp) most refrigerants have a dye in them and it will show up under Black light where the freon is escaping from.