I had a leaking D3 seawater pump. Unfortunately I discovered it too late. The seawater was already dropping on the Alternater and demaged the alternator (it's stupid from Volvo to position the alternator directly under the seawater pump!).
The cause was a worn shaft in the sea water pump. I had to replace both: seawaterpump and alternator! My mechanic suggestet not to do the shaft repair, but to install an new one.
So be carefull: If it's the shaft, it will ultimately ruin the alternater if not changed. The alternator was much more expensive than the pump...
Greeting from Vienna,