[Gunner]

Repeat this mantra about 427 times... oh, sorry, 289 times in your case: "Ammeters are useless window-dressing in modern cars." By modern, I mean any car with an alternator. The generator days were a little different, but with modern alternators and voltage regulators (and I'd bet you have a modern VR, maybe hiding under an era-style case), ammeters are somewhere between chrome knob and idiot light in usefulness.

If you don't want to swap it out for a voltmeter, attach a voltmeter to your electrical system as a test instrument. You should see 11.8-12.2 volts with the engine off, no lower than about 9 volts (maybe 8, with an older battery and big engine) during cranking, and a fairly steady 13.5-14 volts while the engine is running, no matter the RPM or electrical load. Anything else, you've got a problem that's easy to diagnose. Post some numbers if you can.