12 31 009 Checking alternator (BSD)

WARNING: This page is about a different car, the 2010 BMW X3, 2009 BMW X3, 2008 BMW X3, and 2007 BMW X3. However, it is still accessible from the selected car via links, so may be relevant.

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: Oscillogram Graph - Fault-Free Alternator

G04725679

Courtesy of BMW OF NORTH AMERICA, INC.

Oscillogram for a faulty alternator:

One phase interrupted.

Repair/exchange alternator.

Fig 2: Oscillogram Graph - One Phase Interrupted

G04725680

Courtesy of BMW OF NORTH AMERICA, INC.

Interturn fault.

Repair/exchange alternator.

Fig 3: Oscillogram Graph - Interturn Fault

G04725681

Courtesy of BMW OF NORTH AMERICA, INC.

Open circuit in negative diode.

Repair/exchange alternator.

Fig 4: Oscillogram Graph - Open Circuit In Negative Diode

G04725682

Courtesy of BMW OF NORTH AMERICA, INC.

Short circuit in positive diode.

Repair/exchange alternator.

Fig 5: Oscillogram Graph - Short Circuit In Positive Diode

G04725683

Courtesy of BMW OF NORTH AMERICA, INC.

Open circuit in positive diode.

Repair/exchange alternator.

Fig 6: Oscillogram Graph - Open Circuit In Positive Diode

G04725684

Courtesy of BMW OF NORTH AMERICA, INC.

Open circuit in exciter diode.

Repair/exchange alternator.

Fig 7: Oscillogram Graph - Open Circuit In Exciter Diode

G04725685

Courtesy of BMW OF NORTH AMERICA, INC.

Assemble engine.

Check function of DME/DDE.