Set oscilloscope display alternator

The following image represents the voltage curve of an intact alternator. The height of the individual waves depends on the current load of the alternator. The length of the waves depends on the engine speed. The higher the engine speed the shorter the waves.

At idle speed with consumer units switched on, an error-free alternator should provide approximately this waveform:

Fig 1: Display - Intact Alternator Voltage Curve Screen

Courtesy of BMW OF NORTH AMERICA, INC.

The current as a function of engine speed also applies here.

The following example waveforms show alternator with defective diode and alternator with broken coil:

Fig 2: Display - Faulty Alternator Voltage Curve

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 3: Display - Faulty Alternator Voltage Curve

Courtesy of BMW OF NORTH AMERICA, INC.