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100a alternator wiring question.

I agree. The only problem with a voltmeter is that it doesn't show if the alternator is charging the battery, a reading over 12.8 Volts is a good indication of charging, but only a guess...nothing more. An ammeter shows the actual charge/discharge.

PERFECT!!! that's exactly what happens.
 
I have bypassed the bulkhead connectors with the police, taxi, fleet bypass option. I upgraded the alternator to ammeter wire with a new 10 ga wire directly from the alternator through the firewall via the the clutch body plug to the ammeter. I installed a new 10 ga red wire from the battery stud to the ammeter with a fusible link also through the clutch body plug. The original red 10ga from the battery stud through the bulkhead connector has been disconnected and taped to the harness in case I want to put the car back to OEM and the ammeter side has been removed and taped making it a dead wire, but in place for return to original. The original black 12 ga wire from the ammeter is still in place to feed the interior, but has been removed from the alternator and taped. The two charge wires have bypassed the bulkhead connectors.
Headlight relays are powered directly from the alternator. I have the original 44.5 amp alternator and using the headlights at cruise the ammeter barely moves off center. At idle there is a slight discharge with my foot on the brake, but that's what Mopars do. My headlights do not dim at idle. The car is an auto and if I idle in neutral at night, there is barely a discharge. This works for me and I like having the ammeter working. I idle at 800rpm in drive and I could probably eliminate that slight discharge at idle when another 100-150 more rpms. Haven't done that yet as the slight discharge doesn't seem to be an issue.
 
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Nacho has the best explanation. Amps is a measurement of consumption. A good working component draws what it needs to operate. Here's a good example.
Let's say a single headlight is rated at 50 watts.
At 12 volts the lamp will draw 2.08 amps.
With the car is running and the alternator is excited, an alternator puts out more than 12V, let's use 13.5V which is in the ballpark.
At 13.5V the 50 watt headlight consumes 1.85 amps.
In theory, if your old alternator handled your needs and you haven't added any new electric components, the only real advantage will be faster battery recovery.
 
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