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 graphic.

Fig 1: Display - Intact Alternator Voltage Curve Screen

Courtesy of BMW OF NORTH AMERICA, INC.

Examples of faulty alternators are shown below.

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

Fig 2: Display - Faulty Alternator Voltage Curve Screen

Courtesy of BMW OF NORTH AMERICA, INC.

Alternator with defective diode

Fig 3: Display - Alternator With Defective Diode Signal Screen

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Alternator with broken coil