Rotor Open or Short Test

Remove the rotor from the alternator. Place the ohmmeter Multiply-By setting at 1 and calibrate the meter.

NOTE: Text values shown in brackets [ ]___ are referenced to Rotunda Model 059-00010 and may be different if another tester is used.

1. Contact each ohmmeter probe to a rotor slip ring. The meter reading should be 2.0-3.9 ohms.









2. A higher reading indicates a damaged slip ring, welded connection or a broken wire. A lower reading indicates a shorted wire or slip ring. Replace the rotor if it is damaged and cannot be serviced.
3. Contact one ohmmeter probe to a slip ring and the other probe to the rotor shaft. The meter reading should be infinite (no needle movement).









4. A reading other than infinite indicates the rotor coil is grounded to the shaft. Replace the rotor if it is grounded and cannot be serviced.