Each to his own, I know some people like voltmeters over ammeters, and I respect that. I don't want to start a war on this. So this is just one person's opinion:
1. I have had several alternators with my ammeter (1957 Chevy truck), they all worked fine. Assuming it works, the ammeter just measures what is there. Your alternator should be outputting withing the range of the ammeter's capability.
2. I like the ammeter because it shows current, charging or discharging, right away. It is an easy visual to determine the state of your charging system.
3. If the ammeter is wired correctly, and showing minimal deflection, is it possible the alternator is defective or not wired correctly.
Again, voltmeters are some people's preference for a variety of reasons. But I do know an ammeter should work in your scenario if you want that instrument.
don
