19 volts on the battery

Near 15V is a bit high, can still cook a battery long term with that. If you measure between ballast supply (IGN1) and battery terminal you can find the drop in bulkhead connector, ammeter ignition switch and wiring.
IGN1 is the reference for the voltage regulator. It likely measures about 13.8V, but the alternator is putting out a higher voltage at the battery, with the voltage drops in between. Reducing the drops, gets battery voltage correct.