if you've changed to an alternator, it's not a "stock system", when it starts charging will depend on the particular alternator and it's internal [?] regulator .... when you first fire it up, try reving it until you see a charge
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics