Just adding my 2 cents here - typically if the clutch is the problem the noise will mostly be apparent when the A/C compressor is not engaged. Once it is engaged (clutch closed) the whole clutch assembly, including the outer pulley surface, will rotate with the compressor hub, so it should not be making any noise. If the compressor makes noise while it is engaged, most likely the actual compressor is on its way out.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280