12 31 009 Checking alternator (BSD)

WARNING: This page is about a different car, the 2005 BMW 545i and 2004 BMW 545i. 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: View Of Oscillogram For Fault-Free Alternator

G03270219

Courtesy of BMW OF NORTH AMERICA, INC.

Oscillogram For A Faulty Alternator:

One phase interrupted.

Repair/exchange alternator.

Fig 2: View Of Oscillogram For Faulty Alternator

G03270220

Courtesy of BMW OF NORTH AMERICA, INC.

Interturn fault.

Repair/exchange alternator.

Fig 3: View Of Oscillogram Interturn Fault

G03270221

Courtesy of BMW OF NORTH AMERICA, INC.

Open circuit in negative diode.

Repair/exchange alternator.

Fig 4: View Of Oscillogram Open Circuit In Negative Diode

G03270222

Courtesy of BMW OF NORTH AMERICA, INC.

Short circuit in positive diode.

Repair/exchange alternator.

Fig 5: View Of Oscillogram Short Circuit In Positive Diode

G03270223

Courtesy of BMW OF NORTH AMERICA, INC.

Open circuit in positive diode.

Repair/exchange alternator.

Fig 6: View Of Oscillogram Open Circuit In Positive Diode

G03270224

Courtesy of BMW OF NORTH AMERICA, INC.

Open circuit in exciter diode.

Repair/exchange alternator.

Fig 7: View Of Oscillogram Open Circuit In Exciter Diode

G03270225

Courtesy of BMW OF NORTH AMERICA, INC.

Assemble engine.

Check function of DME/DDE.