Bench Testing: Commutator: 4-Cylinder

Place commutator on V-blocks and measure commutator runnout. See Fig 1.
Using vernier calipers, measure the commutator length. Standard length: 0.1299 in. (3.3 mm) Maximum length: 0.1575 in. (4.0 mm). If the length is greater than the maximum, replace the armature. See Fig 2.
Using vernier calipers, measure the brush holder length. See Fig 3. If the length is less than minimum, replace the starter commutator end frame assembly.
Using an ohmmeter, Verify that there is no continuity between the positive and negative brush holders. If the there is continuity repair or replace the starter commutator end frame assembly.

Fig 1: Measuring Commutator Runnout

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Fig 2: Measuring Commutator Length

Fig 3: Testing Commutator End Frame