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HOMESERVICE MANUALSBMW2009335DREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 104 (GENERATORS & REGULATORS)TESTINGGENERATOR & REGULATOR SWITCH
2009 BMW 335d

Generator & Regulator Switch

2009 BMW 335dSECTION Generator & Regulator Switch
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2006 BMW X5, 2005 BMW X5, 2004 BMW X5, 2003 BMW X5, and 2002 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.

Check for correct connections on fully charged battery, generator and starter motor. Check for good ground connection between engine and body. Check for properly tightened drive belt. Connect DIS tester. Search down through the following:

  • FUNCTION SELECTION
  • COMPLETE VEHICLE
  • DRIVE
  • VOLTAGE AND CURRENT REGULATION
  • VOLTAGE AND CURRENT GENERATION
Work through test modules. To diagnose oscillograms for each fault, see GENERATOR OSCILLOGRAMS . If generator is faulty, repair or replace it. To replace generator on 3.0L (M54), see GENERATOR 3.0L (M54)  under REMOVAL & INSTALLATION. To replace generator on 4.4L & 4.6L (M62), see GENERATOR 4.4L & 4.6L (M62)  under REMOVAL & INSTALLATION. To replace generator on 4.4L (N62), see GENERATOR 4.4L (N62)  under REMOVAL & INSTALLATION.

If regulator is faulty, replace it. To replace Bosch regulator, see VOLTAGE REGULATOR (BOSCH) . To replace Valeo regulator, see VOLTAGE REGULATOR (VALEO) . To replace regulator on 4.4L (N62) see VOLTAGE REGULATOR 4.4L (N62) .

GENERATOR OSCILLOGRAMS

Fault Oscillogram
Fault-Free See Fig 1
One Phase Interrupted See Fig 2
Internal Fault See Fig 3
Open Circuit In Negative Diode See Fig 4
Short Circuit In Positive Diode See Fig 5
Open Circuit In Positive Diode See Fig 6
Open Circuit In Exciter Diode See Fig 7
Fig 1: Identifying Oscillogram For A Fault-Free Generator
G00301749Courtesy of BMW OF NORTH AMERICA, INC.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.