So I have this 100 amp alt I want to install but first issue is do I have to upgrade wires and which ones? I currently have a 3 wire alt like the one in photo. Second is what do I do with external regulator? Just unplug it? I don't want to lose my gen dummy light in dash. Thanks, 72 cutlass.

 

The wire you need to upgrade is the one that runs from the threaded BATT terminal on the alternator to the stud on the horn relay. If your original wire has a fusible link in it, you should use a maxi fuse that matches the amperage capability of the new wire.

 

ok thanks, I believe it needs to be a 10 gauge wire. I'll double check. i see the diagram, do I need to reroute the ext regulator wires? Can I just leave it connected or will that confuse the charging system? I mainly just don't want to lose my charging idiot light, don't have a volt meter in car. Thanks

 

The whole point of that diagram is to show you that you disconnect the harness from the external regulator and put jumpers in the connector to bypass it. You can by a pre-made jumper connector for this also, but frankly it's just four spade terminals and two pieces of wire.