If an ohmmeter shows zero ohms between the slip rings and the rotor shaft during an alternator rotor test, what does this indicate?

When an ohmmeter shows zero ohms between the slip rings and the rotor shaft in an alternator rotor test, it indicates a direct electrical connection between the slip rings and the rotor shaft. This condition suggests that there is a short circuit occurring between the rotor winding and the rotor shaft, which typically means that the insulation has failed.

This failure allows electrical current to flow where it should not, potentially leading to performance issues in the alternator and could impact overall vehicle operation. A properly functioning alternator should have high resistance between these components, indicating that the rotor windings are isolated from the rotor shaft. Therefore, the reading of zero ohms is a clear indication of a defect, affirming that the unit is indeed shorted and defective.