12 31 009 Checking Alternator (BSD)

Necessary preliminary tasks: 

• Correct connections on charged battery
• Correct connections on alternator and starter motor
• Good ground connection between engine and body
• Tensioned ribbed V-belt
• Read out DME/DDE fault memory.

BSD alternator can be recognized by the plug connection on the alternator.

Connect diagnosis tester.

• Function selection
• Complete vehicle
• Drive
• Voltage and current regulation
• Voltage and current generation
• Alternator
• Follow instruction in diagnostic program

Oscillogram for a fault-free alternator: 

Fig 1: Identifying Waveform - Fault-Free Alternator

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Oscillogram for a faulty alternator: 

One phase interrupted.

Repair/exchange alternator.

Fig 2: Identifying Waveform - Faulty Alternator (1 Of 6)

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Interturn fault.

Repair/exchange alternator.

Fig 3: Identifying Waveform - Faulty Alternator (2 Of 6)

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Open circuit in negative diode.

Repair/exchange alternator.

Fig 4: Identifying Waveform - Faulty Alternator (3 Of 6)

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Short circuit in positive diode.

Repair/exchange alternator.

Fig 5: Identifying Waveform - Faulty Alternator (4 Of 6)

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Open circuit in positive diode.

Repair/exchange alternator.

Fig 6: Identifying Waveform - Faulty Alternator (5 Of 6)

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Open circuit in exciter diode.

Repair/exchange alternator.

Fig 7: Identifying Waveform - Faulty Alternator (6 Of 6)

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Assemble engine.

Check function of DME/DDE.