Isuzu KB P190. Manual - part 541

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 

STARTING AND CHARGING SYSTEM  6D3-17 

fan. 

 

 

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. 

 

 

STARTING AND CHARGING SYSTEM  6D3-19 

 

Inspection 

Generator 

Before any in field testing can be undertaken it is important 
that the battery's conditions is established and the terminals 
are clean and tight. 
 
Check the condition of the generator drive belt and ensure that 
it is adjusted in accordance with the engine manufacturer's 
recommnedations.  
  
Battery conditions: 
Note: This assessment may be difficult with maintenance free 
assemblies. 
 
Test the specific gravity of the individual cells the readings 
should be within 10 points of each other, it is recommended 
that the average SG should be 1.260 or higher. 
A load test should be carried out to determine the ability of the 
battery to supply and accept current. This is a good indicator 
as to the general condition of the battery. 
A load equal to the normal starting current should be placed 
across the battery, the duration of this load test should not 
exceed 10 seconds, during this time the terminal voltage 
across the battery should not drop below 9.6 volts. Observe 
each cell for signs of excessive gas liberation, usuall an 
indication of cell failure. 
If the battery test is clear proceed with the Generator tests as 
follows. 
 
Care should be taken when making the following connections.
It is recommended that the battery negative terminal be 
disconnected before the test meters are connected, and 
reconnecting the negative terminal when the meters are 
inserted into the circuit under test.  The warning lamp in the D+ 
circuit should not exceed 2 watts. 
 

 

 

Regulating voltage test on the vehicle. 

Connect a voltmeter to the generator, the positive lead to the 
B+ terminal and the nagative lead  to the generator casing. 
Select the voltage range to suit the system, i.e. 20v for 12 volt 
sysytems or 40v for 24 volt systems.  Connect an ammeter in 
series with the main output cable from the B+ terminal on the 
generator, the range selected must be capable of reading the 
maximum output from the generator. 
 
Note the voltmeter reading before starting the engine. This 
reading should increase when the engine is running indicating 
generator output, start the engine and increase the engine 
speed until the generator is running at 4000 rpm, switch on 
vehicle loads of 5-10 A is indcated on the ammeter, the 
voltmeter shoud read 14.0-14.2 v for a 12 volt system, for a 24 
volt system the readings should be 5-10 A and 27.7-28.5 volts.