Nice video.
The only bone I have to pick with it is about what he called the field connection, which I was calling armature current. That is how the voltage regulator controls the alternator output. I've seen this in two configurations: pull it to +12 volts, or pull it to ground, to put full power to the armature. In operation, the regulator watches the battery during run to hold the battery voltage at 14 volts or so, using the field ( armature current ) as the feedback control.
So, it's gonna vary, depending on how much juice you need to maintain 14 volts on the battery rail.
Your alternator uses more advanced technology which also sends a sample of one phase of the stator voltage to the regulator.
There are auto shops that specialize in electrical stuff that can thoroughly check out your alternator in minutes, in place, with a test load and an oscilloscope. What their test load will do is put max load on the alternator, and they will simultaneously verify all three phases of the alternator stator windings and all diodes. Any shorted windings or bad diodes will show up on the oscilloscope display. They know exactly what to look for, and getting their approval of your alternator status may give you some peace of mind before a road trip.
I hate to advise you to change out expensive parts when I know the technology is out there to quickly and inexpensively diagnose alternators... you don't even have to remove it from the truck. ( It needs the truck to spin it during the test anyway ). They know what all the currents and voltages should be and give you wise counsel.
But I would advise you to seek counsel on a possible bad diode in the three phase bridge. This is indicated by your lower than expected alternator output voltage.
I found another video you may find helpful:
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