Rotor Test

Using an ohmmeter, check for continuity between rotor and slip rings. Perform STEP 1. See Fig 1. If continuity exists, replace rotor.

Fig 1: Testing Alternator Rotor
Courtesy of GENERAL MOTORS CORP.
Using an ohmmeter, check for continuity between slip rings. Perform STEP 2. See Fig 1. If continuity does not exist and resistance is not within 2.8-3.0 ohms, replace rotor.