Isuzu N-Series. Manual - part 540

Engine Electrical   6D-27

Remove the brushes and commutator carefully so
as not to allow them in contact with the adjacent
parts.

7. Bolt
8. Torsion Spring
9. Magnetic Switch Assembly

Remove the magnetic switch bolts, then remove
the switch from the shift lever.
Remove the torsion spring from the magnetic
switch.

10. Dust Cover
11. Shift Lever
12. Bearing Retainer
13. Clutch Assembly

1) Remove the bearing retainer.
2) Remove the clutch assembly from the gear

case.

14. Bearing Holder
15. Ball Bearing
16. Pinion Stopper Clip
17. Pinion Stopper
18. Return Spring
19. Pinion Shaft
20. Pinion Clutch

Use a screwdriver to remove the stopper clip. Then
disassemble the clutch assembly.

N6A0998E

N6A0999E

N6A1000E

N6A1001E

6D-28   Engine Electrical

Inspection and Repair

Make the necessary adjustments, repairs, and part
replacements if excessive wear or damage is
discovered during inspection.

Armature

1. Measure the commutator run-out.

Replace the commutator if the measured run-out
exceeds the specified limit.

2. Check the commutator mica segments for

excessive wear.

3. Measure the mica segment depth.

If the mica segment depth is less than the standard
but more than the limit, the commutator may be
reground.
If the mica segment depth is less than the limit, the
commutator must be replaced.

4. Measure the commutator outside diameter.

Commutator Run-Out

mm (in)

Standard

Limit

0.05 (0.002) or less

0.2 (0.008)

N6A1002E

N6A1004E

Mica Segment Depth

mm (in)

Standard

Limit

0.5 — 0.8 (0.020 — 0.031)

0.2 (0.008)

Legend

1. Insulator
2. Commutator Segments

N6A1005E

N6A1006E

Engine Electrical   6D-29

If the measured outside diameter is less than the
specified limit, the commutator must be replaced.

5. Test the armature for short circuiting.

1) Place the armature in a growler tester.
2) Hold a hacksaw blade against the armature

core.
If the armature has a short circuit, the hacksaw
blade will vibrate.
Replace the armature if there is a short circuit.

6. Use a circuit tester to check the armature for

grounding.

1) Hold one probe of the circuit tester against the

commutator segment.

2) Hold the other circuit tester probe against the

armature core.

If the circuit tester indicates continuity, the
armature is grounded.
The armature must be replaced.

7. Use the circuit tester to check the armature for

continuity.

1) Hold the circuit tester probes against two

armature core segments.

2) Repeat Step 1 at different segments of the

armature core.

There should be continuity between all segments
of the armature core.
If there is not, the armature must be replaced.

Yoke

1. Use a circuit tester to check the field winding

ground.

1) Hold one circuit tester probe against the field

winding end or brush.

Commutator Outside Diameter

mm (in)

Model

Yoke 

Diameter

Standard

Limit

S25-505G

φ90

36.5 

(1.437)

35.5 

(1.398)

N6A1007E

N6A1008E

N6A1009E

N6A1010E

6D-30   Engine Electrical

2) Hold the other circuit tester probe against the

bare surface of the yoke body.

There should be no continuity.
If there is continuity, the field coil is grounded.
The yoke must be replaced.

2. Use the circuit tester to check the field winding

continuity.

1) Hold one circuit tester probe against the “C”

terminal lead wire.

2) Hold the other circuit tester probe against the

field winding brush.

There should be continuity.
If there is no continuity, the yoke must be replaced.

Brush and Brush Holder

1. Use a vernier caliper to measure the brush length

(four brushes).

Replace the brushes as a set if one or more of the
brush length is less than the specified limit.

2. Use a circuit tester to check the brush holder

insulation.

Touch one probe to the holder plate and the other
probe to the positive brush holder.
There should be no continuity.

3. Inspect the brushes for excessive wear.

If the negative brushes have excessive wear, the
entire brush holder assembly must be replaced.
If the positive brushes have excessive wear, only
the brushes must be replaced.
1) Use a pair of side cutters to cut the lead wire

from the brush.

N6A1011E

N6A1012E

Brush Length

mm (in)

Model

Yoke 

Diameter

Standard

Limit

S25-505G

φ90

15.0 

(0.591)

10.5 

(0.413)

N6A1013E

N6A1014E