Outer Limits 4x4 Board

got an old datsun 720 4x4 ute replaced alt with 2nd handy from wrecker and replaced the external (on fire wall) regulator and cleaned up wiring now the battery light on the dash is still on after all this ShortyIQ around can any body help as im in a bit of a prediciment
Cheers Bourkey

Also i dont know a great dealto do with the external reg so if any 1 can let me kno how they work and what not