I have a 03 2500 HD 31,000 miles , while the A/C is on it makes a hissing noise. It still works fine; cold air and everything. I took it into the dealer today and the mechanic today me " the air compessor is still new and it's getting to know it's self" and some other monkey buzinus. Now I don't claim to know anything about A/C's but I know a little about cars and that's the first time I've heard that (my grandfather is ASE certified) I'm in the military so it's to far for him to look at it. Has anyone else had this problem? Thanks

 

I get the same noise on my 05 silverado. I'm taking it in today to have them check it out.