12 31 009 Checking Alternator and Regulator Switch

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.

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





If charge indicator lamp goes out while engine is running:
Check control voltage.
Regulator switch must be replaced if control voltage is not achieved.
Replace alternator regulator switch.





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:





Oscillogram for a faulty alternator:
One phase interrupted.
Repair/exchange alternator.





Interturn fault.
Repair/exchange alternator.





Open circuit in negative diode.
Repair/exchange alternator.





Short circuit in positive diode.
Repair/exchange alternator.





Open circuit in positive diode.
Repair/exchange alternator.





Open circuit in exciter diode.
Repair/exchange alternator.