David -
It all depends on your skill level , and financial situation . If you have deep pockets , but no multi-meter ; By all means let the dealer handle it .
But if you want to fix it yourself , and have access to a multi-meter and know how to use it ; by all means delve further into it . The 275 GT has a garden variety stator under the flywheel that should put out at least twice the needed charging voltage in alternating current (typically 32-40 volts at WOT) . Then that voltage gets converted to Direct Current in the rectifier part of your Rect./Regulator (at roughly half of stator output 16-20V DC ) . Next the regulator part is designed to turn on and off the voltage back to the system-(battery) to maintain it at the proper voltage . This all depends on good connections at all major points of grounds , and all electrical connectors involved at the engine harness , rect./reg. , stator , battery , Ect.., Etc..,
So that is where to start ; Scrutinize every electrical connection Pos. and Grounds . I've
even seen the magnets in the flywheel come unglued , causing zero stator output .
Hope you find your gremlin . Dave