A/C groan. Clutch or compressor??

[Bryan Foster]

Listers,
I have developed a loud groan from the a/c compressor that only occurs
when I switch the a/c on (i.e. when the clutch is engaged.)  My question
is, how can I tell if this is just a bad clutch bearing vs. a bad internal
compressor bearing?  Are there any differentiating characteristics I
can use without just buying a new clutch?  A/c still blows cold.

Thanks in advance.
Bryan Foster