I've had my 01 Z3 3.0 for about a year. I've taken the car in twice to the shop for what seems to me like charging or hissing noise when the A/C is on. SWISHHHH..... SWISHHH. SWISHHHHH......on, off the on again. The dealer says one of two things they don't hear the damn thing- although it sound s like a bee's nest- or it's normal. This can't be normal. :dunno: