The only time terminals are jumpered is during the polarizing procedure, and only for one second or so. With the engine off, touch a jumper wire from the Bat. terminal to the A terminal. You'll get a small arc- - - -that's normal. Just don't leave the jumper connected for more than about one second. Polarizing creates "residual magnetism" in the generator armature, which is necessary for the generator to begin charging. A properly polarized generator will have approximately 1/2 volt present at the armature terminal with the engine running, with no wires connected to the generator. Because the field coils on a GM generator get their excitation from the armature, the F terminal will also have that 1/2 volt present when the generator is turning with no wires attached. If the F terminal is jumpered to ground, the voltage at the open A terminal will spike to a very high number, 40 or 50 volts in some cases. That is a pretty good method of determining if the generator is capable of producing charging voltage.
Once you're sure the generator can produce voltage, connect all the wires to the regulator, and crank the engine up. Be sure there's a ground wire between the generator housing and the regulator base. Rusty body/frame mounts can cause all sorts of charging system problems if the regulator can't find a good ground back to the engine. The regulator is controlling the output of the generator by changing the resistance of the F terminal ground circuit. A good ground is a must! As Armature voltage rises above about 12.5 volts, the cutout relay closes, and current flows from the generator to the battery, recharging it. As the battery charges, the armature voltage rises, keeping charge current flowing. The voltage regulator limits the voltage as it reaches about 14.7 volts to prevent overcharging. Dirty or burned points inside the regulator on the units behind the F and A terminals will prevent the field circuit from being completed, giving the generator no output.
DO NOT SAND OR FILE REGULATOR POINTS! They will stick, and cause the battery to be overcharged. Clean regulator points with a piece of business card or a strip of clean index card material. Have fun!
Jerry
