12 31 009 Checking alternator and regulator switch

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  .

Fig 1: Identifying Checking Carbon Brush Length

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If charge indicator lamp goes out while engine is running:

Check control voltage. Refer to 12 32 REGULATOR E36 .

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

Replace alternator regulator switch. Refer to 12 32 501 REPLACING VOLTAGE REGULATOR  .

Oscillogram For A Fault-Free Alternator: 

Fig 2: Identifying Fault-Free Alternator Oscillogram

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Oscillogram For A Faulty Alternator: 

One phase interrupted.

Repair/exchange alternator.

Fig 3: Identifying Oscillogram One Phase Interrupted

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Interturn fault.

Fig 4: Identifying Interturn Fault

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Repair/exchange alternator.

Open circuit in negative diode.

Repair/exchange alternator.

Fig 5: Identifying Open Circuit In Negative Diode

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Short circuit in positive diode.

Repair/exchange alternator.

Fig 6: Identifying Short Circuit In Positive Diode

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Open circuit in positive diode.

Repair/exchange alternator.

Fig 7: Identifying Open Circuit In Positive Diode

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Open circuit in exciter diode.

Repair/exchange alternator.

Fig 8: Identifying Open Circuit In Exciter Diode

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