While driving my Camry around town my Air Conditioning is always running fine and blows out cold air with no problem. The problem is that most of the time when I have my A/C on, and come to a full stop at a stoplight or street sign, it seems as if my engine or some part of the A/C unit starts vibrating and making a loud clattering sound. Even while making this loud vibration it still blows cold air, but the sound is just very annoying. Nothing happens when I have the heat or defrost on, so it is definitely the A/C unit.