Isuzu engine 4j series. Service manual - part 90

6D3 – 18  CHARGING SYSTEM

3. Separation of Pulley, Fan, Drive End Frame, and Rotor

Fix the rotor in a lock vice, and after removing the lock nut
separate the pulley, fan, drive end frame, and rotor.

NOTE:

Be sure to fix the rotor through cloth in a vice.

4. Removal of Bearing (on the Drive End Frame Side)

•

Remove the ball bearing fixing screw.

•

As shows in the illustration, make the drive end frame
parallel to a block, and then push out the bearing with
a press through a jig.

5. Separation of Rear End Frame and Rectifier & Stator

Remove the nuts M5 and M6, and separate the rectifier
and stator from the rear end frame.

6. Separation of Rectifier and Stator

Disconnect the stator lead wire from the rectifier by means
of a soldering copper to separate the rectifier and stator
from each other.

NOTE:

Since the rectifier a low resistance to heat, the work
should be done quickly using radio pliers to absorb
heat.

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CHARGING SYSTEM  6D3 – 19

7. Removal of Bearing (on the Rear Side) [Only for

Replace.]
Take out the bearing with a puller.
Insert it to see whether replacement is needed.

NOTE:

Conduct the bearing inspection mentioned below and
determine whether or not the bearing be replaced.

INSPECTION AND REPAIR

NOTE:

Standard values and limits vary with alternators, and
therefore, maintenance standards for each part
should be followed.

1) Fan

Check to see whether it is deformed.

2) Bearing

Turn it by hand to check for smooth and noiseless
turning.

3) Stator
•

Resistance between phases (neutral point and each
phase lead wire) should be 1

Ω

 or less.

•

Insulation resistance between the core and stator coil
should be 0.1M

Ω

 or more by a 500V megohmmeter.

NOTE:

If there is no continuity, the connection of lead wire
should be checked as the disconnected stator coil
cannot be considered.

4) Rotor
•

Resistance between slip rings as shows in the
illustration, about 4

Ω

.

•

Insulation resistance between slip ring and ball core:
0.1M

Ω

 or more by 500V megohmmeter.

•

Check slip rings for surface. If staind or rough, use
sand paper (#300 - #500).

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Tighten the lightly with
a vise with care not to
cause any damage

.

6D3 – 20  CHARGING SYSTEM

In this case, the slip ring can be used until its outer
diameter becomes 0.4mm shorter than the initial size.

5) Rectifier

Conduct a rectifier continuity test using the K

Ω

 range

of a circuit tester.
Specifically, change polarity between the rectifier and
holder fin, making sure that there continuity in either
one direction only. (There should not be continuity in
the other direction.)

NOTE:

It is impossible to judge a rectifier by the resistance in
the direction of easy flow. Because of diode’s
characteristics, the current in the direction of easy
flow changes greatly depending on the power source
voltage.

Therefore, a tester’s indication varies depending on
its type and resistance range variation.

Accordingly, it must be regarded as a criterion that
there is a wide difference between the resistances
easy flow and the other direction.

Never use a 500V megohmmeter for such a continuity
test, since the rectifier may be damaged.

6) Brush

Measure the protruding length from the brush holder.

mm (in)

Standard

Limit

12.5 (0.492)

5.5 (0.217)

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CHARGING SYSTEM  6D3 – 21

REASSEMBLY

Follow the same procedure as for disassembly in the
opposite order, paying special attention to the following
points:
•

Brush
When fitting a new brush, be sure to see it so that the
free end of it is projecting 12.5mm (0.49 in) from the
holder.

•

Rotor

Be sure to fit it after brush is supported by the brush
holder.
Otherwise, the rotor cannot be fitted or the brush may
be broken.

Output Characteristic

As alternator speed increases, the output gradually
increases as shows in the illustration.
In other words, when alternator speed exceeds a certain
limit to cause to enlarge output current, supply capacity will
further increase owing to the neutral point diodes.

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