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 For A Fault -Free Alternator

Courtesy of BMW OF NORTH AMERICA, INC.

Oscillogram for a faulty alternator:

Fig 2: Identifying One Phase Interrupted

Courtesy of BMW OF NORTH AMERICA, INC.

One phase interrupted.

Repair/exchange alternator.

Interturn fault.

Fig 3: Identifying Oscillogram For Interturn Fault

Courtesy of BMW OF NORTH AMERICA, INC.

Repair/exchange alternator.

Open circuit in negative diode. Refer to Figure .

Repair/exchange alternator.

Short circuit in positive diode. Refer to Figure .

Repair/exchange alternator.

Open circuit in positive diode. Refer to Figure .

Repair/exchange alternator.

Open circuit in exciter diode. Refer to Figure .

Repair/exchange alternator.

Assemble engine. Check function of DME/DDE.