a/c noise

1999 cirrus w/ v6 , 100k miles,The engine makes loud groaning noise that changes when a/c is switched on my feeling is that it is the a/c clutch and or compressor is shot any thoughts before i start buying parts?

A technic I use to use is remove the belt or belts and turn all accessories by hand to feel for any grinding , you can also crank it with the belts off mometerily to make sure it it is not internal , hope this can help .