My 2007 S60 2.5T displays a warning light saying the charginging system service urgent. It only seems to come on when we have a heavy rain. I replaced the alternator with the correct one for the Eurpoean market, although I live in the states. The part number crossed to the European one. I have the correct amperage, 140. The light went out after I installed it but every time it rains...here it is again. Any ideas?

 

Maybe not a big help but rain maybe means water leaks on an exposed wire/connector. Or the alternator pulley is tired (assuming it was used part)

 

The warning is actually POWER SYSTEM SERVICE URGENT. Not much difference but it could be significant. Thanks for the response. I've been looking in the cargo area for possible leaks. that might be the problem I going to try taping some connections back there and tie wrapping some to get them off the floor.