charging problem

Hi guys, I have a problem with my charging system, I recently did the amp meter bypass on it and now I'm getting 15 volts while it's running. I've already read some threads on here with similar problem but I've gotten to a point of scratching my head. I have excellent grounding with 0.00 ohms everywhere, I get no voltage loss that I can tell. I get 12.4 volts at the battery, and 12.4 volts everywhere else, even at the fuse panel, my bulkhead connectors are in really good shape considering it's 41 years old, not corroded or burnt. I put a new voltage regulator in so it wasn't that causing the problem, the alternator is a few years old. I'm not sure what else there is to check. Anyone got any other ideas?