@panterapatt posted:The original ammeters jumped back and forth until the shunts were installed across the terminals. I replaced mine with a VDO ammeter which shows either positive charge or negative discharge with a very steady needle. Lance Nist installed the shunt on my stock original gauge and it was steady during operation. Your ammeter should not be "flatline" (which I assume you mean 0 +/-) if there is load on the system. But I do remember that my stock gauge with the shunt barely moved one way or the other. Hence my other reason for replacing it.
This is because the shunt was poorly calibrated.
With a correct shunt the ammeter should vary significantly but without reaching its maximum capacity.
It is normal for the charging current to be higher after a start, since the starter has discharged the battery a little. Then when the battery has regained its full charge, the alternator regulates the energy it produces according to the load of the different receivers and the ammeter is therefore very close to zero.
It is only when consumption is higher than the maximum power of the alternator that it indicates a negative current, which means that the battery is discharging and that it is necessary, if possible, to reduce consumption by switching off non-essential equipments.