At Model

Check the commutator for signs of seizure or stepped wear. If the symptom is minor, use sandpaper to repair. If it cannot be repaired, replace the armature assembly.
Measure runout on the commutator.
Commutator runout:

Standard

0.02 mm (0.0008 in)

Limit

0.05 mm (0.0020 in)

Courtesy of SUBARU OF AMERICA, INC.

(A) Dial gauge

(B) V-block
Measure diameter of the commutator.
Commutator diameter:

Standard

29 mm (1.1417 in)

Limit

28 mm (1.1024 in)

Courtesy of SUBARU OF AMERICA, INC.

(A) Diameter

Measure the depth of the segment mold.

Depth of segment mold:

Standard

0.70 mm (0.0276 in)

Limit

0.20 mm (0.0079 in)

Courtesy of SUBARU OF AMERICA, INC.

Check the continuity in the commutator segment. If there is no continuity, replace the armature assembly.

Courtesy of SUBARU OF AMERICA, INC.

(A) Commutator segment
Check insulation between the commutator segment and armature core. If there is continuity, replace the armature assembly.

Courtesy of SUBARU OF AMERICA, INC.

(A)	Commutator segment
(B)	Armature core

(A)	Dial gauge
(B)	V-block