What should you check if the ammeter shows no readings?

When the ammeter shows no readings, checking the alternator's functionality is crucial because the alternator is responsible for generating electrical power and charging the battery during flight. If the alternator is not functioning properly, it will not produce the necessary current to show on the ammeter. This could indicate a failure in the alternator or an issue in the charging system, which can lead to an inadequate power supply for the aircraft's electrical systems.

The other factors, while they may be important in the broader context of flight operations, do not directly relate to the ammeter's readings. The fuel level pertains to the aircraft's ability to maintain power from the engine but does not influence the electrical system. The battery condition is relevant when assessing overall electrical performance but is usually indicated by an ammeter reading; if the alternator is working correctly, the battery should remain charged. The throttle position affects engine performance rather than the electrical output monitored by the ammeter. Therefore, focusing on the alternator is the most logical step in determining why the ammeter shows no readings.