Starting System & Charging System: Generator: Inspection: Rotor

Inspect the slip rings for contamination or any roughness on the sliding surface. Repair the slip ring surface using a lathe or sand paper.
Measure the slip ring outer diameter. Replace the rotor if the slip ring is worn.
Slip ring outer diameter:

Standard

22.7 mm (0.894 in)

Limit

22.1 mm (0.870 in)
Using a circuit tester, check the resistance between slip rings. If resistance exceeds the standard, replace the rotor.
Standard:

Approx. 2.0 - 2.3 Ω

Fig 1: Checking Resistance Between Slip Rings
Courtesy of SUBARU OF AMERICA, INC.
Check the continuity between slip ring and rotor core or shaft. If there is continuity, replace the rotor because the rotor coil is grounded.

Fig 2: Checking Continuity Between Slip Ring And Rotor Core Or Shaft
Courtesy of SUBARU OF AMERICA, INC.
Check the bearings. If there is any noise, or the rotor does not rotate smoothly, replace the bearings.