How do i test a 380sl fan clutch
 

With the engine hot and at idle I can stop the fan with my hand, and when I run up the rpm's (3000) i can still hold the fan without feeling it trying to turn. Is this normal or a bad fan clutch. Also this is a new clutch (sachs) and there is thumping sound coming from the clutch that goes away in about 4 or 5 turns of the fan when I first start the engine. All the bolts are tight and the fan is seated on the pully. Any thoughts.

bad fan clutch
 

No, that is a bad fan clutch, you should not be able to hold with your hand while the car is running (be careful doing that), use a piece of wood instead. If you car is getting over 90 when you're idling or stuck in traffiic you should change this fan clutch, but if not it could be controlled by the temp and at the time you're holding it does is not engaged.