Inspecting Components of Alternator

INSPECTING COMPONENTS OF ALTERNATOR

- Perform tests with a BMW service tester.
- Checking Rotor Coil for Breaks and Shorted Turns:





- Connect test leads for resistance test on slip rings.
- For 80 A alternator: 2.8 to 3.0 ohms.

Checking Rotor Coil for Ground Contact;





- Connect test leads for resistance test on slip ring and rotor shaft.
- Nominal value: infinity 999 k-ohm display.
- Check slip rings, fine grinding if necessary.

Checking Stator Coil for Ground Contact:
- Connect test leads for resistance test on solder point and stator (coil carrier).
- Nominal value: infinity 999 k-ohm display.

Checking Stator Coil for Breaks:





- Compare resistance values of wires 1/2, 1/3 and 2/3 with an ohmmeter - they should be identical.
- The shorted turn test can be performed with a standard tester.

Checking Negative Diodes:





- Connect test leads for diode test.
- Negative lead on cooler and positive lead on one of the negative diode connections.

Display with perfect condition diodes;
- polarity "-".

Checking Positive Diodes:





- Connect negative lead on B + connection pin and positive lead on one of the positive diode connections.

Display with perfect condition diodes:
- polarity "+".








- If a diode is defective, replace entire diode plate.