First off let me say i know NOTHING about a/c its one thing i have never delt with and my dad was an automotive a/c guy for 30 years haha. Anyways its blowing fine and all and i can hear the compressor engaging and disengaging but its not cold. I figure with the miles it has it prob just needs freon. However before i throw freon into it i wanna see if it has a leak. Where do i start?