Had a warning last night on my tdi. Firstly the battery light came on, then a few secs later it read "Alternator Workshop". Im not mechanical at all so i dont know what this means. however its gone now, but the guard that protects the engine underneath is shagged and hanging down, now when i turn the wheel left or right i get a terrible noise, like the noise of an old car starting up if u get me?? lol any ideas? and whats this alternator do?