What is the item that you are cooling the "Head Unit"??? Please use the proper terminology such that appropriate advice can be issued. It sounds as though the Alternator is good but the wiring is faulty and not connecting the alternator to the battery properly. Do you have the wiring diagram for the 240Z? What is the "Digital Gauge"???...
Blog 19685
This is EXTREMELY interesting. Would like to do the same and also fab a duct with a smaller opening to the radiator. The desire is to get aero such that my 240Z is stable at higher speeds and also get VERY good cooling of the radiator.

