Starter No-Load Test
- Connect a tachometer, ammeter and voltmeter into starter circuit. See Fig 1. Using carbon pile, adjust voltage to 10 volts and engage starter motor.
- Read amperage draw and armature speed to ensure they are within specification. See the STARTER NO-LOAD SPECIFICATIONS . If exact voltage cannot be obtained and voltage is slightly higher than specification, RPM should also be slightly higher. Alternatively, carbon pile may be adjusted to reduce voltage.
- Low free speed (no load) and high current draw indicates too much friction, shorted armature, or grounded armature or fields. Failure to operate with high current draw indicates a direct ground in terminal or fields, or frozen bearings.
- Failure to operate with no current draw indicates an open field, open armature coils, broken brush springs, worn brushes, or high commutator insulation.
- If free speed (no load) is low and low current draw exists, suspect high internal resistance due to poor connection, defective leads or dirty commutator. A high free speed and high current draw usually indicates shorted fields.
Courtesy of GENERAL MOTORS CORP.