I have a 2012 with 30k miles. Last year the ac unit was replaced. Today its 40 degrees out. It sounds like the blower is on , if you put your hand over the defroster you feel heat, but it will not blow out. Also when you shut it off, it sounds like its full of sand or something. Someone told me if you push off and defrost at the same time it will give you diagnostic codes, I cant get that to happen.