12v Cummins swap gauge wiring

[John-e Bravada]

I asked this in the Interior forum ( http://www.gmsquarebody.com/forum/showthread.php?t=7771 ) without a conclusive answer. I have completed the engine swap and now I'm on to trying to make the factory gauges work. Water temp check, oil pressure check , battery voltage.....? On the BBC alt there was a brown wire which from the Chilton's wiring diagram comes from the volt gauge. The gauge seems to function without it hooked up but I don't see how it's working if this is supposed to be wired to an output of the alternator or grounded.

Has anyone hooked up their volt gauge after a CTD swap and if so how?

 

[cat-black]

the gauge is an ampmeter right? so its wired between the alternator and battery, to show charging..
if it's just a check light, then I'm not sure
but I'm going to need the same info soon!