When I turn my A/C on there is a noise coming from my engine? When I turn my A/C off the nosie stops? A coworker said it could be the belt tenssioner but I think it could be my A/C. I A/C seems cool when I drive but when at a stand still the air gets warm? Could it be just the barrings or is my A/C going out? Has anyone had this issue before?

Thanks for your help

Gary