Check commutator for any sign of burns of rough surfaces or stepped wear. If wear is of a minor nature, correct it by using sandpaper.
Check the commutator run-out and replace if it exceeds the limit. See Fig 1 . See STARTER SPECIFICATIONS table under STARTER SPECIFICATIONS.
Check the depth of segment mold. See Fig 2 . See STARTER SPECIFICATIONS table under STARTER SPECIFICATIONS.
Check armature for short-circuit by placing it on growler tester. See Fig 3 . Hold a iron sheet against armature core while slowly rotating armature. A short-circuited armature will cause the iron sheet to vibrate and to be attracted to core. If the iron sheet is attracted or vibrates, the armature, which is short-circuited, must be replaced or repaired.
Using a circuit tester, touch one probe to the commutator segment and the other to shaft. See Fig 4 . If there is no continuity, it is normal. If there is continuity armature is grounded. Replace armature if it is grounded.

Fig 1: Testing Commutator Run-Out

Courtesy of SUBARU OF AMERICA, INC.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Bench Testing: Armature