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Starter No-Load Test

CAUTION: DO NOT  apply more voltage than specified. Excessive voltage may cause armature to throw windings due to excessive speed.
  1. Secure starter in vise. Turn carbon pile off and open switch. Connect test equipment to starter as illustrated. See Fig 1. Turn switch on and adjust carbon pile until voltage is 10 volts. See STARTER NO-LOAD TEST SPECIFICATIONS  table. Check ammeter reading and pinion speed on RPM indicator. Turn off carbon pile and open switch. Compare RPM and amperage readings with specifications. Refer to the STARTER NO-LOAD TEST SPECIFICATIONS  table.
  2. If amperage and RPM readings are as specified, starter motor is okay. If test indicates low free speed and/or high current draw, unit may have tight, dirty or worn bearings or bushings, shorted or grounded armature, or a grounded field.
  3. High current draw with pinion moving into cranking position but no pinion rotation indicates a direct ground in field, or frozen bearings or bushings. No pinion movement and a normal current reading indicates plunger is unable to move into solenoid or drive is unable to move on armature shaft. No pinion movement and very low or no current draw indicates an open or ground in solenoid windings.
  4. Pinion moving into cranking position but not turning and very low current draw indicates an open in field circuit or armature windings, or no current flow between solenoid battery and motor field terminals while motor is engaged. Connect a jumper wire between solenoid battery and motor field terminal "M". If motor now turns at specified RPM, replace solenoid.
  5. Low no-load and low current draw indicates high internal resistance due to poor brush lead connections; a dirty commutator; an open in armature windings; broken, worn or weak brush springs; or worn, damaged or dirty brushes. High no-load speed and high current draw indicates shorted field coils or shorted armature windings. If starter vibrates or is noisy, armature may be rubbing against inside of frame and field.
Fig 1: Starter No-Load Test Connections
G95I13472Courtesy of GENERAL MOTORS CORP.
STARTER NO-LOAD TEST SPECIFICATIONS

Application (1) Amps Starter RPM
PG260 65-95 8500-10,700
28MT 130-190 2300-5600
(1) At 10 volts.
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