12 31 009 Checking alternator and regulator switch

WARNING: This page is about a different car, the 2003 BMW X5, 2002 BMW X5, and 2001 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.

Test Requirements:

Correct connections on charged battery.
Correct connections on alternator and starter motor.
Good ground connection between engine and body.
Tightened drive belt.

Connect DIS Tester:

Measurement.
Checking alternator.

If charge indicator lamp is permanently lit:

Remove voltage regulator and check carbon brushes, replace if necessary.

Replace alternator regulator switch. Refer to 12 32 501 REPLACING VOLTAGE REGULATOR (VALEO/BOSCH) .

NOTE: Minimum length of carbon brushes "A" = 5 mm.

Fig 1: Identifying Minimum Length Of Carbon Brushes

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If charge indicator lamp goes out while engine is running:

Check control voltage. Refer to ENGINE ELECTRICAL SYSTEM - TECHNICAL DATA .

Regulator switch must be replaced if control voltage is not achieved.

Replace alternator regulator switch. Refer to 12 32 501 REPLACING VOLTAGE REGULATOR (VALEO/BOSCH) .

From E46/E39 With Multifunction Regulator:

Recognizable by plug connection on regulator.

Connect DIS Tester.

Function selection.
Complete vehicle.
Drive.
Voltage and current regulation.
Voltage and current generation.
Work through test modules.

Oscillogram For A Fault-Free Alternator:

Fig 2: Oscillogram For Fault-Free Alternator

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Oscillogram For A Faulty Alternator:

One phase interrupted.

Repair/exchange alternator.

Fig 3: Oscillogram For Faulty Alternator

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Interturn fault.

Repair/exchange alternator.

Fig 4: Oscillogram For Interturn Fault

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Open circuit in negative diode.

Repair/exchange alternator.

Fig 5: Oscillogram For Open Circuit In Negative Diode

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Short circuit in positive diode.

Repair/exchange alternator.

Fig 6: Oscillogram For Short Circuit In Positive Diode

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Open circuit in positive diode.

Repair/exchange alternator.

Fig 7: Oscillogram For Open Circuit In Positive Diode

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Open circuit in exciter diode.

Repair/exchange alternator.

Fig 8: Oscillogram For Open Circuit In Exciter Diode

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