Component Tests and General Diagnostics

Open Circuit Test
An open circuit starter motor armature may sometimes be detected by examining the commutator for evidence of burning. A burn spot on the commutator is caused by an arc formed every time the commutator segment, connected to the open circuit winding, passes under a brush.

Grounded Circuit Test
This test will determine if the winding insulation has been damaged, permitting a conductor to touch the starter frame and magnet or armature core. To determine if the armature windings are grounded, check with ohmmeter. Infinite resistance indicates a normal condition.