Starting/Charging Systems (H4SO): Generator: Inspection: Rotor

Inspect the slip rings for contamination or any roughness of the sliding surface. Repair the slip ring surface using a lathe or sand paper.

Measure the slip ring outer diameter. If the slip ring is worn replace rotor assembly.

Slip ring outer diameter: 

Standard 

22.7 mm (0.894 in) 

Limit 

22.1 mm (0.870 in) 

Check the resistance between slip rings using circuit tester.

If the resistance is not within specification, replace the rotor assembly.

Specified resistance: 

Approx. 1.8 - 2.2 Ω 

Fig 1: Performing Continuity Test

Courtesy of SUBARU OF AMERICA, INC.

Check the continuity between slip ring and rotor core or shaft. If resistance is 1 Ω or less, the rotor coil is grounded, and so replace the rotor assembly.

Fig 2: Performing Insulation Test

Courtesy of SUBARU OF AMERICA, INC.

Check the rear ball bearing. Replace if it is noisy or if the rotor does not turn smoothly.