Check the voltage across the battery terminals with the engine OFF by setting your volt meter to 20 volt scale. Attach positive lead to positive battery terminal. Attach negative lead to negative battery terminal. Voltage should read around 12.5 volts. Then start the engine, the voltage reading should spike up to 13.8 - 14.2 volts. That indicates the alternator is charging. Turning the headlights and heater ON, the 13.8 - 14.2 volts should still remain the same.I don't have one. All I have is a regular meter. Check voltage at battery with a load. Like headlights on. Voltage should stay fairly steady?