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Home >> BMW >> 2009 >> X5 35d >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 14 (Engine Electrical System - Repair (N52)) >> Alternator With Drive And Mounting >> 12 31 009 Checking Alternator (BSD)

12 31 009 Checking Alternator (BSD)

WARNING: This page is about a different variant/trim than selected.

Necessary preliminary tasks: 

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.

Oscillogram for a fault-free alternator: 

Fig 1: Wave Form Graph - Fault-Free Alternator
G04740394Courtesy of BMW OF NORTH AMERICA, INC.

Oscillogram for a faulty alternator: 

One phase interrupted.

Repair/exchange alternator.

Fig 2: Wave Form Graph - One Phase Interrupted
G04740395Courtesy of BMW OF NORTH AMERICA, INC.

Interturn fault.

Repair/exchange alternator.

Fig 3: Wave Form Graph - Interturn Fault
G04740396Courtesy of BMW OF NORTH AMERICA, INC.

Open circuit in negative diode.

Repair/exchange alternator.

Fig 4: Wave Form Graph - Open Circuit In Negative Diode
G04740397Courtesy of BMW OF NORTH AMERICA, INC.

Short circuit in positive diode.

Repair/exchange alternator.

Fig 5: Wave Form Graph - Short Circuit In Positive Diode
G04740398Courtesy of BMW OF NORTH AMERICA, INC.

Open circuit in positive diode.

Repair/exchange alternator.

Fig 6: Wave Form Graph - Open Circuit In Positive Diode
G04740399Courtesy of BMW OF NORTH AMERICA, INC.

Open circuit in exciter diode.

Repair/exchange alternator.

Fig 7: Wave Form Graph - Open Circuit In Exciter Diode
G04740400Courtesy of BMW OF NORTH AMERICA, INC.

Assemble engine.

Check function of DME/DDE.

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