Component Tests and General Diagnostics

CHECKING ALTERNATOR AND VOLTAGE REGULATOR

Testing Requirements:





- Correct connections on charged butylate
- Correct connections on alternator and starter
- Good ground connection between engine and body.
- Tight drive wit.

Indicator Lamp On Continuously:





- Remove voltage regulator and check carbon brushes, replacing if necessary.
- Distance "V" for new condition = approx 12 mm (0.472").

Installation Note:





- Check slip rings for wear, fine grinding and polishing if necessary.
- Connect BMW service test unit.
- Start engine and compare test values with nominal values.





- If the battery charge indicator lamp goes out while engine is running and the regulating voltage is not reached - harmonic wave ratio and oscillograph okay (as shown) - the voltage regulator has to be replaced.





- Repeat test.
- If the specified charging current is not reached, remove and disassembly alternator, and inspect components - 12 31 020/513.

Oscillographs of Defective Alternator:





- Defective power or exciter diode.





- Shorted turn of stator coil.





- Break in one exciter diode.