Battery light on dash. Battery (calcium) seems fine. Tested the battery with engine on and it seems to have been overcharging. 

Unplugged the smart charger and alternator runs fine at the default 13.8. So alternator looks good. 

Only getting ~6v on the battery link(red wire) at the 3 pin plug on the alternator (the fused connection link in the image below). I've run a temporary fused link straight to the battery and all is working as it should.

So now I just need to install a new connection cleanly. And preferably without totally ripping open all the cable sleeves from alternator to battery. Does anybody have a wiring diagram for this? Or know where I could find one? I'm presuming this red wire travels to the relay/fuse box in the engine bay. I opened the box and can see two red wires (amongst many others) entering. Both show as 12+v, neither gives a positive for continuity (given the wire must be damaged somewhere along the way probably doesn't rule them out). If I knew which one it is I could join here at the relay/fuse box and run it back to the alternator (tucking it into the wiring sleeve). But I don't know which one it is. Or if it even is one of those two. 

Would greatly appreciate it if somebody could tell me or point me towards a diagram that shows where that red wire ends up at the battery/fusebox end? 

 

I'm presuming I could also make a fusible connection to the B post on the alternator? But I'd prefer to go the original route. 

In case anyone comes here looking for advice in the future, I found the corroded section of wire. It was located about half of its way across the engine bay, at it's lowest point, just at the coolant hose clip.

Ran a new wire to the plug and jobs a goodun.