indigof

Hello guys, i have got a 2004 E60 3.0 diesel. Lately i have been having this weird issue: Sometimes the alternator stops charging, i get electrical failures all over the place, e.g.: automatic gearbox fails to shift up, the wipers are going very slowly. When the car is cold - the charging is bad, when the car is hot - it gets back to normal. I have already changed the alternator and nothing has changed. Any suggestions what might be wrong?