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: Oscillogram For Fault-Free Alternator

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Oscillogram for a faulty alternator: 

One phase interrupted.

Repair/exchange alternator.

Fig 2: Oscillogram For Faulty Alternator - One Phase Interrupted

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Interturn fault.

Repair/exchange alternator.

Fig 3: Oscillogram For Faulty Alternator - Interturn Fault

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Open circuit in negative diode.

Repair/exchange alternator.

Fig 4: Oscillogram For Faulty Alternator - Open Circuit In Negative Diode

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Short circuit in positive diode.

Repair/exchange alternator.

Fig 5: Oscillogram For Faulty Alternator - Short Circuit In Positive Diode

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Open circuit in positive diode.

Repair/exchange alternator.

Fig 6: Oscillogram For Faulty Alternator - Open Circuit In Positive Diode

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Open circuit in exciter diode.

Repair/exchange alternator.

Fig 7: Oscillogram For Faulty Alternator - Open Circuit In Exciter Diode

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Assemble engine.

Check function of DME/DDE.