Rotor Test

Test rotor for grounded, open or shorted field coils using an ohmmeter. Test for ground by connecting an ohmmeter between each slip ring to the rotor shaft. No continuity should exist or rotor is grounded. Check for an open field by connecting an ohmmeter across slip rings. A reading of 1.5-2.5 ohms indicates normal resistance. Readings above 3.5 ohms indicate high resistance and rotor replacement may be necessary. If reading is 1.5 ohms or less, field coil is shorted.