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Rotor Open Or Short Circuit Test

  1. Remove rotor from alternator. Set ohmmeter to "x1" range. Connect each probe to one rotor slip ring. Meter should read 2.0-3.9 ohms resistance. Higher readings indicate damaged slip ring solder connection or broken wire.
  2. Lower readings indicate shorted wire or slip ring. Replace rotor if damaged. Connect one ohmmeter probe to one slip ring and other probe to rotor shaft. Ohmmeter reading should be infinity. Readings other than infinity indicate rotor is shorted to shaft. Replace rotor if shorted.
ALTERNATOR SPECIFICATIONS

Application In. (mm)
Brush Length
New .48 (12.2)
Wear Limit .25 (6.4)
Slip Rings
Maximum Runout .0005 (.013)
Minimum Diameter 1.2 (30)