So I kept hearing this grinding sound and took my car in to the service dept at the dealership. The mechanic drove it, heard it (thank gosh) looked it up, and said it was a problem Nissan already knew about. I understand it as cruddy gunk gets into the fan blower from where the windshield wipers are and so they are replacing the blower and installing a screen to keep the junk out. I'm not excited about things Nissan knows about but doesn't send courtesy letters to owners. This is my fifth trip in since I bought the car five months ago.