Bench Testing: Rotor

Inspect slip ring brush contact surface. If surface is worn or rough, smooth surface with fine emory paper. Measure slip ring diameter. See SLIP RING DIAMETER table. If diameter is not as specified or brush contact surface is excessively worn or damaged, replace slip rings and/or rotor.
Resistance across rotor slip rings should be about 3 ohms. See Fig 1 . If resistance is not as specified, replace rotor. Check continuity between each slip ring and rotor core/shaft, individually. See Fig 2 . Continuity should not exist. If continuity exists, rotor coil and/or slip ring is grounded. Replace rotor.

Fig 1: Checking Resistance Between Slip Rings

Courtesy of SUBARU OF AMERICA, INC.

Fig 2: Checking Continuity Between Slip Ring & Rotor Core Or Shaft

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SLIP RING DIAMETER

Standard - In. (mm)	Limit - In. (mm)
.894 (22.7)	.870 (22.1)