Starter Armature: Testing and Inspection

Armature Inspection:

1. Inspect the armature surface for wear or damage.

Checking The Commutator Diameter:

2. A dirty or burnt commutator surface may be resurfaced with emery cloth or a lathe within the following specifications.

Commutator Diameter
Standard (New): 28.0-28.1 mm (1.102-1.106 in)
Service Limit : 27.5 mm 11.08 in)

Checking The Commutator Runout:

3. If the commutator runout and diameter are within limits, check the commutator for damage or for carbon dust or brass chips between the segments.

Commutator Runout
Standard (New): 0-0.02 mm (0-0.0008 in)
Service Limit : 0.05 mm (0.002 in)

Cleaning The Commutator:

4. If the surface is dirty, recondition it with a #500 or #600 sandpaper. Then, check mica depth. If necessary, undercut the mica with a hacksaw blade to achieve proper depth.

Commutator Mica Depth
Standard (New): 0.4-0.5 mm (0.016-0.020 in)
Service Limit : 0.15 mm (0.006 in)

Checking For Continuity:

5. Check for continuity between the segments of the commutator. If an open circuit exists between any segments, replace the armature.

Armature Testing:

6. Place the armature on an armature tester. Hold a hacksaw blade on the armature core. If the blade is attracted to the core or vibrates while the core is turned, the armature is shorted. Replace the armature.

Armature Inspection And Identification:

7. With an ohmmeter, check that no continuity exists between the commutator and armature coil core, and between the commutator and armature shaft. If continuity exists, replace the armature.