When sitting at idle for a while, the fan clutch should start to gradually spin the fan faster and faster.
The fan clutch freewheels below 92C and then starts to engage more and more and should be fully locked by around 95C, maybe a little higher. If it holds the engine temps below 100C and you can hear the fan pull air through when the engine is revved, then I would say that it is fine.
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record