another not charging thread

ALL these old girls will have SOME drop. A couple -4 tenths is not going to cause a reduced charge condition (to the VR/ field circuit) it is going to rather cause OVER voltage, OVER charge. This is because the VR keeps ramping up the field to keep the VR IGN terminal at the VR setpoint, which should be about 14. When that happens, the battery will run ABOVE that voltage by the amount of the TOTAL drop from battery neg to VR case, and from battery POS all the way through the harness and to the VR IGN terminal.

MAYBE the alternator is not putting out it's rated power and MAYBE it's either a too small unit or has an electrical problem

"The way to tell" ultimately is to make up a pair of say, no14 wires long enough to jumper straight battery power direct to the two field terminals. With the battery up and all loads on, a slow rise in RPM should easily raise the battery voltage to 16+ and I would not allow it past that. IF YOU HAVE a battery load tester (carbon pile) you can dial in load amps and see just what it will keep up with. In other words, dial in say, 50A on the load tester, raise engine RPM with field wired direct, and the battery should sit no less than "about" 13V or more.