If the OP hadn't had the ammeter he wouldn't have know the system had issues. Even adding a voltmeter, which I always do, would not have revealed an issue until the battery was seriously overcharged - in this matter it's like an idiot light that tells you that you are screwed, too late. As it is the ammeter immediately showed an issue and allowed the OP to find the issue and correct it. Yeah the original ammeter was never made to last 50 years, probably not 20. If you are concerned unhook the original, leave it in place and install a modern high quality ammeter under the dash and hook the wires to it. We at FABO are, in general, folks that monitor and repair our vehicles. Never bypass a critical diagnostic tool when it might save your bacon.