My '12 3.6r currently has 12,000mi. For the last 8,000-10,000mi, the A/C compressor has been making two continuous and loud noises, one of which was repaired yesterday by the dealership:
Noise 1): Repaired yesterday when the A/C compressor was replaced. When the a/c is on, there is an intermittent knocking/tapping noise, like tapping an empty coffee can with your knuckles. The dealership figured this was the a/c clutch going out, and replaced the compressor under warranty. This noise is now gone, but.....
Noise 2): When the a/c is on, there is a loud fluid rushing noise, like something you would hear if someone was upstairs running a shower or faucet and you heard water flowing in the pipes overhead. We hoped this noise might be related to Noise 1 and that it might go away after replacing the compressor. Well, it is completely unchanged after swapping it out.
When I cycle the a/c off (leaving the fan on), the fluid rushing noise immediately stops, and resumes when I cycle it back on. There is no performance issue with the system, it's plenty cold, I'm just getting tired of having to have the radio on when I come to a stoplight so I don't feel like I need to pee all the time from hearing a constant waterfall in the engine bay! I have owned roughly 10 other cars in my day and none of them has ever made this kind of noise. My '10 LGT also never made this noise.
I appreciate any insight anyone might have into this problem, especially my fellow 3.6r'ers. The car is otherwise flawless, this tiny little issue is just bugging the crap out of me though!