Merc Spritner 311CDi

Have a 52reg sprinter 311cdi.
couple of annoying little thigns with it.
the cooling fan seems to be in all the time (clutch mechanism on the front
of the block) whcih makes it quite noisy. any ideas as toa sensor that could be acting up etc etc
also. just below the fuel filter there is a 3 pin connector, this seems to be broken, any ideas what this is for, is it the connector for the sensor that shows water in teh fuel filter?
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