Isuzu engine C22NE / 22LE / 20LE. Service manual — part 41

STARTING AND CHARGING SYSTEM 6D3-15

Positive heatsink

8 diode

6 diode

H

G

Negative heatsink

C

B

A

Starpoint

F

E

B+Bolt

D

Diode connections

Stator connection

1.1

Power Diodes.

Apply the negative test probe of the diode tester or a
multimeter with a diode test feature to the positive heatsink and
the positive probe alternatevely to A,B,C, a low resistance
reading, or the forward voltage drop across the diode shoud be
obtained. Reverse the test probes, a high resistance reading or
a higher reverse voltage should be obtained.

Now connect the positive test probe to the negative heatsink
and the negative alternatively to D,E,F, a low resistance or
forward voltage drop across the diode should be obtained.
Reverse the test probes, a high resistance reading or a higher
reverse voltage should be obtained.

For 8 diode rectifier plates tests for G and H should be
included. When the reverse voltage test is done the applied
voltage should be less than 14 volts DC or 12 volts RMS for
AC testers.

1.2

Zener Diode

The basic tests in 1.1 should be undertaken first before the
diode zener voltage is tested. Diodes are grouped together
according to their zener voltag i.e. all diodes within a rectifier
must have the same zener voltage.

Connect the test probes as for the reverese test listed above
i.e. reverse biased apply the test voltage form the zener diode
tester (current limited to 5ma) and read to zener breakdown
voltage this should be a steady reading and not increase with
increased voltage from the tester.

6D3-16 STARTING AND CHARGING SYSTEM

Readings for Zener diode groups 011 to 042

Zener voltage at
5Ma.

Positive
diode

Negative
diode

Fordward
current Rating

17.8v-19.2v

011

012

25A

18.8v-20.2v

013

014

25A

19.8v-21.2v

015

016

25A

20.8v-22.2v

017

018

25A

21.8v-23.2v

019

020

25A

22.8v-24.2v

021

022

25A

17.8v-19.2v

031

032

35A

18.8v-20.2v

033

034

35A

19.8v-21.2v

035

036

35A

20.8v-22.2v

037

038

35A

21.8v-23.2v

039

040

35A

22.8v-24.2v

041

042

35A

Note: Diode number is stamped on the rear of the diode.

2. Stator

Inspect the stator insulation resistance to ground with an
insuation tester or a series test lamp up to 110 volts.
The insulation resistance must be greater than 1 megohm.
The winding reisistance is measured between phases using a
low reading ohmmeter designed for this purpose, the values
are given at the rear of this instruction.

3. Rotor

Inspect the rotor for insulation resistance to ground using an
insulation tester or a series test lamp up to 110 volts.
The insulation resistance must be grater than 1 megohm.
Measure the rotor resistance between the sliprings using an
ohmmeter or apply 12 volts across the sliprings and measure
the rotor current flow, then divide 12 by the measured current,
the results is the rotor resistance in ohms. values are given at
the rear of this instruction.

If the sliprings are worn or out of round they must be re
machined to a minimum diameter or 26.7 mm and should have
a runout not exceeding 0.060mm. If the slipring is below these
limits it must be replaced with a new one.

Warning; extreme care must be exercised when machining
the slipring as it is possible for the turning tool to foul the fan.

STARTING AND CHARGING SYSTEM 6D3-17

4. Replacing the brushes (inbuilt regulator)

Check the brushes for length, this is measured from the brush
holder to the end of the brush along it's centre line. Also
inspect for any sideways wear. If worn replace both brushes.
The minimum length is 3.8mm. Inspect the brush springs for
signs of corrosion or loss of tension or uneven tension.

Replacing the brushes, using a soldering iron apply heat to the
soldered joints on the rear of the brush holder of the regulator,
using a small lever prise up the retaining tabs to release the
brush lead and spring. Thread the new brush lead up the
brush holder along with the spring, pull the lead through the
tabs until the brush is protruding 12mm from the holder.
Bend down the tabs and solder the brush lead taking care not
to allow the solder to run up the lead which will reduce
flexibility. Use 60/40 resin cored solder.

5. Ball bearing

Please note the bearings used in this KCA generator are a high
tolerance type, only fully sealed bearings of the same
specification are to be used as replacements. It is
recommended that the bearings be replaced during the
reconditioning process to restore the unit to original
specification.

6. Regulator

The regulator can only be tested when fitted into an altenator.

Warning: do not reverse"S" and "L" connections or put 12
volt supply to "L" terminal, this connection must not be
used as a supply source other than to supply the
requirements of the warning lamp 2(watts).
Such action will destroy the regulator warning lamp
circuit.

For test voltages refer to Generator output testing section.
See also additional information on regulator function earlier in
this instruction.

6D3-18 STARTING AND CHARGING SYSTEM

Reassembly

Generator

(a) Press new bearing onto slipring end of the rotor taking care

to aplly the force to the bearing inner race only, otherwise

the bearing will be noisy and it's life will be shortened.

(b) Fit a new bearing to the drive end housing, fit the bearing

plate, and four retaining screws, press the rotor into the

bearing, using a support tool to take the thrust against the

bearing inner.

The support is fitted from the pulley side of the bearing. In

this way the thrust is not taken by the drive end housing.

(c) To fit pulley, mount an 8mm Allen key in the vice with the

short end upwards, place a 24mm ring spanner on the shaft

nut, position the internal hexagon of the rotor shaft onto the

Allen key, tighten the nut to the required torque(See torque

chart)

(d) Inspect the bearing support ring for signs of damage, if in

doubt replace the ring by pressing it into the housing by

hand, do not use excessive force.

(e) To refit the rectifier, fit new mica washers to the positive

heatsink B+ bolt and retaining screw each washer must

have heatsink compound applied to both surfaces before

fitting.

Fit the three retaining screws to the rectifier then install into

slipring end housing. Tighten the B+ bolt to the reuired

torque.

(f) To refit the stator, make sure the spigot surface are clean

and free from damage, fit the stator into the slipring end

housing noting the correct lead connection positioning. Fit

the stator leads into the wire loops in the recrifier. Using a

pair of pliers squeeze the loop to retain the stator lead prior

to soldering. Repeat for each lead in turn, solder the leads

into position using 60/40 resin cored solder. Make sure the

leads will be clear of the internal fan when the rotor is

assmebled into the stator.

(g) Carefully install the rotor into the stator/slipring end housing

assembly, noting the alignment of the housings and through

bolt holes. Fit the through bolts making sure the stator is

seated correctly, tighten the through bolts to the correct

torque setting (uneven torque can produce magnetic noise

levels above normal).

(h) Fitting the regulator. Compress the brushes into the brush

holder by hand, slip the regulator through the opening in the

rear of the slipring end housing until the brushes come in

contact with the slipring. Press the regulator towards the

slipring until the holes are aligned then fit the retaining

screws and tighten.