The charging system can easily be tested if the load current is known. Because the shunt is in series with the battery we don?t know system load current when the engine is running. So with the engine at operating temperature and the battery fully charged turn the engine OFF. Look at the ammeter, it will be display an nice stable negative value. This is the system load current. Now find the RPM that corresponds to the absolute value of this load current from the graph in section ?
2.2.1) Requirements for flawless operation of the rectifier-regulator? of the Installation manual (who says Rotax doesn?t have a sense of humor.) here?s a screenshot
Start the engine and set the RPM to the value from the graph. Your voltage should stabilize at or above 13.5 volts. The failure mode of the regular is no output or half wave output. A faulty regulator will be obvious by the very low battery voltage displayed.