If your wiring is correct, your ammeter should show a charging state when the engine is first started, to restore the power used by the starter, then should level off to no charge. To test your ammeter, turn on your A/C, headlights and blower motor with the key in the "run" position. The needle should indicate a discharge state. Start the car, and it should indicate charge state if you run the engine fast enough for the alternator to generate enough current to charge the battery.