Starter No Load Test

CAUTION: Refer to Battery Disconnect Caution in Cautions and Notices.

CAUTION: Refer to SIR Handling Caution in Cautions and Notices.

1. Secure the starting motor in a vise or suitable test stand.
2. Turn OFF the carbon pile and open the switch.

CAUTION: Keep fingers, tools, and any other objects away from the opening in the drive end housing while making electrical connections. The strong shifting action of the starter solenoid can cause severe personal injury or damage to components as the drive pinion moves into the cranking position.




3. Connect a voltmeter from the starter motor terminal to the starter motor frame (ground), as shown.
4. Connect the starter motor and an ammeter in series, from the positive terminal of a fully charged 12 V battery.
5. Connect a switch from the S terminal of the starter solenoid to the starter motor terminal.

NOTE: Never operate the starter motor for more than 30 seconds at a time. Allow it to cool for at least two minutes. Overheating, caused by too much cranking, will damage the starter motor.

6. Close the switch.
7. Adjust the carbon pile load to obtain 10 V on the voltmeter.
8. Note the following meter readings:
^ The armature speed on an RPM indicator.
^ The current draw on an ammeter.
9. Turn OFF carbon pile and open the switch.
10. Compare the measurements with the specifications. Refer to Starter Motor Usage. [1][2]Electrical Specifications

The test results indicate the following conditions:
^ Rated current draw (amps) and rated no-load speed (RPM) indicate the normal condition of the starter motor.
^ Low, no load speed (RPM) and high current draw (amps) indicates too much friction, causing the armature to drag. This can result from any of the following conditions:
- Tight, dirty, or worn bushings or bearings
- A grounded or shorted armature
- Grounded fields
^ Failure to operate (no RPM), with high current draw (amps), indicates the following conditions:
- A direct short to ground in the starter terminal or in the fields.
- Seized bearings (This should have been determined by turning the armature by hand).
^ Failure to operate (no RPM), with low or no current draw (amps), indicates the following conditions:
- An open field circuit
- An open in the armature coils
- Broken brush springs
- Worn brushes
- High insulation between the commutator bars or other causes which would prevent contact between brushes and commutator.
^ Low, no load speed (RPM) and low current draw (amps), indicates a high internal resistance caused by the following conditions:
- Poor electrical connections
- Defective electrical leads
- Other causes listed under Failure to operate (no RPM), with low or no current draw (amps), above.
^ High, no load speed (RPM) and high current draw (amps) normally indicates shorted fields.