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.

NOTE: The alternator with BSD interface can communicate with the engine control unit (DME/DDE).

The alternator is not connected to the charge telltale light.

The alternator can identify various faults.

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 Oscillogram Waveform (Fault-Free Alternator)

G03306249

Courtesy of BMW OF NORTH AMERICA, INC.

Oscillogram For A Faulty Alternator:

One phase interrupted.

Repair/exchange alternator.

Fig 2: Identifying Oscillogram Waveform (One Phase Interrupted)

G03306250

Courtesy of BMW OF NORTH AMERICA, INC.

Interturn fault.

Repair/exchange alternator.

Fig 3: Identifying Oscillogram Waveform (Interturn Fault)

G03306251

Courtesy of BMW OF NORTH AMERICA, INC.

Open circuit in negative diode.

Repair/exchange alternator.

Fig 4: Identifying Oscillogram Waveform (Open Circuit In Negative Diode)

G03306252

Courtesy of BMW OF NORTH AMERICA, INC.

Short circuit in positive diode.

Repair/exchange alternator.

Fig 5: Identifying Oscillogram Waveform (Short Circuit In Positive Diode)

G03306253

Courtesy of BMW OF NORTH AMERICA, INC.

Open circuit in positive diode.

Repair/exchange alternator.

Fig 6: Identifying Oscillogram Waveform (Open Circuit In Positive Diode)

G03306254

Courtesy of BMW OF NORTH AMERICA, INC.

Open circuit in exciter diode.

Repair/exchange alternator.

Fig 7: Identifying Oscillogram Waveform (Open Circuit In Exciter Diode)

G03306255

Courtesy of BMW OF NORTH AMERICA, INC.

Assemble engine.

Check function of DME/DDE.