OK, I'll make some educated guesses, but actual measurements will vary somewhat:
Battery: (engine off) 5.9-6.1 Volts
Engine running, cutout relay closed: 6.5-7.5, depending on the state of charge of the battery. If the battery is fully charged, 7.5 Volts +/- a couple of tenths.
Armature: While charging with the cutout relay closed, about 1 or 2 tenths of a volt higher than battery terminal voltage.
Field: This voltage will vary widely, depending on the operation of the voltage and/or current regulator points. Measuring voltage at the field terminal, either generator or regulator, is a waste of time.
UNLESS YOU HAVE AN ACCURATE AMMETER TO CHECK THE CURRENT OUTPUT OF THE ARMATURE, ALL VOLTAGE READINGS ARE VIRTUALLY WORTHLESS. Both voltage and current measurements are needed to accurately check a generator-type charging system.
Here's how it works: The properly polarized generator develops a very low voltage due to a property called "residual magnetism". Without any wires connected to the generator, it should produce about .5 volts at both the armature and field terminals (engine running, of course). The regulator takes this low voltage from the field terminal,and runs it to ground through the voltage regulator points and the current regulator points, in series with each other. When the field current goes to ground, it increases the magnetism in the field coils, which causes the armature voltage to rise.
When armature voltage rises to approximately 6.5 volts, the cutout relay should close, allowing armature current to go to the battery. As long as the armature voltage remains higher than battery voltage, the battery will recharge, and the ammeter on the dash will indicate in the + direction, or "charge", whichever way it's labeled. A dash ammeter is a "wild-azz-guess" indication- - - -not accurate enough to measure actual charge current!
As the battery recharges, the current regulator might begin to operate to keep the generator from overloading itself. When these points open momentarily, a resistance is inserted in the field circuit which reduces the armature output. When the current drops to a safe level, the points reclose and the generator goes back to full output. The points vibrate several times a second to regulate the current flow to 25-30 amps, depending on generator capacity.
Once the battery recharges somewhat, the current regulator stops functioning and the voltage regulator points take over to prevent overcharging due to high armature voltage. Most 6 volt system regulators are set at around 7.5 volts.
THE STATE OF CHARGE OF THE BATTERY IS THE ULTIMATE VOLTAGE-CONTROLLING FACTOR. NO CHARGING SYSTEM WILL DEVELOP MORE VOLTAGE THAN IS NECESSARY TO PUSH A CHARGE INTO THE BATTERY. A battery that is badly discharged might show charging current going into the battery at 6.5 volts or so, while a fully-charged battery might take 7.5 volts to receive the same amount of current.
Cutout relay, current regulator, and voltage regulator points are adjusted by changing the spring tension on the points. Regulators aren't all that mysterious, but they MUST be adjusted accurately, using the proper equipment. A $5.00 digital multimeter from Auto Zone IS NOT the right equipment!
Jerry
