finger test doesnt quite work, specially if you have one of the tropical clutches, the best is the cold start test. Its a hydrostatic clutch. Once you understand how it works - you can diagnose it very quickly.
I have revived a lot of mercedes benz and BMW fan clutches too - those are not serviceable (not screws or bolts on it) And to test them you need to do the cold test. Its the best way to service these hydrostatic clutches.