Armature
- Verify that there is no continuity between the commutator and the core at each segment using an ohmmeter. If there is continuity, replace the armature. (Scheme 8)
- Verify that there is no continuity between the commutator and the shaft using an ohmmeter. If there is continuity, replace the armature. (Scheme 9)
- Place the armature on V-blocks, and measure the runout using a dial indicator. If not within the specification of, runout 0.002" (0.05 mm) maximum, repair using a lathe or replace the armature. (Scheme 10)
- Measure the commutator diameter. If not within the minimum specification, standard commutator diameter 1.16" (29.4 mm), minimum commutator diameter 1.13" (28.8 mm), replace the armature. (Scheme 11)
- Measure the segment groove depth of commutator. If not within the minimum specification, undercut the grooves to the standard depth. Standard depth is 0.016-0.023" (0.4-0.6 mm), minimum depth 0.008" (0.2 mm). (Scheme 12)
Scheme 8
Scheme 9
Scheme 10
Scheme 11
Scheme 12
Magnetic Switch
- Inspect for continuity between terminals (S) and (M) using an ohmmeter. If there is no continuity, replace the magnetic switch. (Scheme 13)
- Inspect for continuity between terminal (S) and the body using an ohmmeter. If there is no continuity, replace the magnetic switch. (Scheme 14)
- Verify that there is no continuity between terminals (M) and (B) using an ohmmeter. If there is continuity, replace the magnetic switch. (Scheme 15)
Scheme 13
Scheme 14
Scheme 15
Brush & Brush Holder
- Verify that there is no continuity between each insulated brush and the plate using an ohmmeter. If there is continuity, replace the brush holder. (Scheme 16)
- Measure the brush length. If any brush is worn almost to or beyond the minimum specification, replace all the brushes. Standard brush length is 0.48" (12.3 mm). The minimum brush length is 0.28" (7.0 mm). (Scheme 17)
- Measure the brush spring force using a spring balance. If not within the minimum specification, replace the brush spring. Standard spring force is 4.12-5.59 ft. lbs. (18.3-24.9 N.m) The minimum spring force is 1.3 ft. lbs. (5.9 N.m). (Scheme 18)
