How to do you read the alternator gauge?
Does he have a bunch of thing pulling power at the battery????
That would show an overcharge condition when in fact it was just providing energy to those accessories.
Very good point If you add power drawing accessories to a system on the "wrong side" of the ammeter ("alternator gauge") it causes the thing to read incorrectly.
When something like factory headlights are wired in, without the engine running, the headlights show a draw on the meter, "neg" or left of center. When the alternator brings that back to zero, or center, the alternator is making up for the headlights, and no additional charge is going to the battery. When the meter goes right of zero, there is charge going to the battery. You, the driver don't know if this is because the battery is low, or if the thing is overcharging.
But when you add something like fans, stereo, pumps and power it off the battery direct, or the starter relay stud, this puts the accessory on the WRONG SIDE of the ammeter, and when you power up the load, the meter will not show discharge (not running) but when running, the meter will always show a charge which is the current the alternator puts through the ammeter to run the accessory
On ANY ammeter hookup, (not counting the starter) all accessories and loads are on the same side of the ammeter as the alternator/ generator. ONLY the battery is on the opposite side