I have a 1966 mustang with factory air original set up. The compressor is quiet when the a/c is running but has a growl/whine when the a/c is off. Also when the a/c is on I can see sparking and arcing between the clutch and the clutch brush. Your thoughts comments appreciated.

 

If it's original from 1996 and you live in Texas, you probably just need to replace the AC Clutch assembly.