For the last 6 month or so a distinct noise right behind the center vents has developed. I suspect it's refrigirant compressing/decompressing while the compressor cylcles. It's very loud (sort of like one hears the flow of boiling fluid), especially when the engine is turned off. First dealer replaced orfice tube, nothing changed, now (4 months later), recharged the system. noting doing. The answer I get "they all do that". I had not had this problem for the first three years.

Can one suggest if there is a fix, or what the problem might be?

Thanks

-J