My alternator belt snapped a while back, but I fitted a new one and everything was fine. Last night however, driving in thick mist and rain, the batt light came on, and has not gone off since. It dims,and gets stronger when u flick wipers or windows etc. The belts still on and still spinning too. Any ideas? Tighten belt? Alternator knackered?

 

i had this happen to mine it was the earthing point behind the speaker in the drivers side footwell, also check the connections on the alternator, might be loose.