Isuzu engine C22NE / 22LE / 20LE. Service manual - part 40

STARTING AND CHARGING SYSTEM  6D3-11

Warning

Do not reverse S and L connections as this will destroy the
warning lamp circuit of the regulator.
Ensure good electrical contact beween generator  earth and
battery negative,

Operation

With the Iginiton switch turnded "ON", current is supplied via
the warning lamp to the "L" terminal of the regulator. Base
current is fed to T15 causing it to turn on, current then flows
from B+ through the rotor winding via the regulator brushes
and the collector emitter junction of T15 to earth completing the
circuit.  The current in the rotor causes a magnetic field
between adjacent poles to be created, this field is rotated and
cuts the windings of the stator at right angles inducing a
voltage into them.
As the speed is increased this induced voltage increases and
results in curent being rectified in the 3 phase diode bridge and
supplied as DC to the B+ output and hence to the battery.
When the voltage at the B+ terminal of the battery reaches
around 14.2 volts, this voltage is monitored by the "S" lead and
turns the regulator Hybrid base current to T15 OFF removing
rotor current, resulting in a decrease in output voltage to below
the regulating voltage, T15 base current turns ON and the
whole cycle is repeated very rapidly.
D38 protects T15 and the regulator against the back voltage
developed across the rotor winding when T15 turns OFF.
The new generated EP regulators incorporate current limiting in
the warning lamp circuit.

Backup Regulation

The EP regulator will limit the output voltage to a safe level
should either the main B+ cable or the battery sense wire
become decoupled, the output voltage will be slightly above the
normal setting(1-3 volts).

Start up phase

When the Iginition switch is turned on and the engine is not
running, the current to the rotor is reduced by switching it on
and off at a 50% duty cycle, the frequency is approximately 4
KHz and may be audible at times.
This is quite normal, once the engine is started normal
regulation commences.

Warning lamp failure

Should the warning lamp fail, the generator will self excite by
deriving a small current from the phase connecion allowing the
voltage to build up to regulating level.
Note: no filed current will flow when the engine is cranking.

6D3-12  STARTING AND CHARGING SYSTEM

Diagnosis

The EP regulator incorporates diagnostics which will illuminate
the warning lamp as a result of fault conditions in the generator
and external circuitry.

These conditions include:
1. An open circujit in the regulator battery sensing wire (S

Terninal)

2. An open circuit or excessive voltage drop in the B+ cable.

3. An open circuit in the generator phase connection.

4. Overcharging of the battery.

5. Regulator output stage short circuit.

6. Open circuit rotor.

The regulator compares the voltage at B+ with the voltage at
the "S" terminal connceted to battery positive.  If the voltage
differential exceeds a predetermined threshold, the regulator
will operate in backup mode to limit the output voltage to a safe
level.  The warning lamp; will remain illuminated as along as
these conditions prevail.
Sources of high resistance which will trigger the warning lamp
are:

a. Poor contact in wiring harness connectors.

b. Poor contact between rectifier and regulator.

c. High resistance in fusible link assembly.

Caution:
When bench testing the generator it is important that the
warning lamp wattage of 2 watts is not exceeded.
Reversal of the "S" and "L" on the regulator will damage
the regulator.
The correct plug for the regulator is a 9 122 067 011 for the
Bosch tye and for the Shinagawa connector the number is
X02FW.

See appendix 1 for daignostic matrix.
Before testing or disassembling the generator please observe
the following points.

1. When testing the diodes with AC type testers the RMS.

Vlotage output must not exceed 12.0 volts, it is

recommended that the stator should be disconnected

during this test.

2. Where zener power diodes are used, the breakdown

voltage should be tested to ensure all diodes have the same

zener voltage.

3. Insulation tests on the rotor and stator should use a voltage

not exceeding 110v for a series test lamp.  The rectifier

must be disconnected from the stator prior to testing.

4. When carrying out repairs to the charging system always

disconnected the battery negative first, and reconnect it last.

STARTING AND CHARGING SYSTEM  6D3-13

5. During current output tests please make sure that the

ammeter is securely connceted into the charge circuit.

6. Some battery powered timing lights can produce high

transient voltages when connected or disconnected.  Only

disconnect or connect timing lights when the engine is

switched off.

7. Make sure the warning lamp circuit is functioning normally

before commencing tests.

8. Battery isolation switches must only be operated when the

engine is stopped.

9. To protect the charging system when using 240 volt

chargers it is recommeneded that the battery is

disconnected whilst charging.

10.Due to the very low resistance value of the stator winding it

may not be possible to obtain accurate readings without

special equipment.

11.12 volts must never be connected to the "L" terminal of the

regulator as this will damage the lamp driver circuit.

12.No loads apart from the warning lamp can be connected to

the "L" termainal.  The "W" terminal is provided for this

purpose.

Disassembly

1. Mark the relative positions of the end housings in relation to

the stator assembly to aid reassembly.  Use a permanent

marking pen do not use centre punched as this can cause

misalignmnet of the housings.

2. Remove the EP regulator from the slipring end housing by

removing the two screws. Tilt the regulator slightly from the

plug connectin until the regulator clears the housing, then lift

clear.

3. Remove the four through bolts.

4. Carefully remove the stator assembly along with the slipring

end housing taking care not to put strain on the stator wires.

5. To disconnect the stator from the rectifier assembly, grasp

the stator wires close to the wire loop with a pair of long

nosed pliers, heat the joint with a soldering iron, when the

point becomes plastic apply a slight twisting motion to the

wires, then pull upwards to release the wires. Remove the

stator.

This procedure opens the wire loop to release the stator

connections easily.

6. To remove the rectifier remove the three retaining screw

and the B+ terminal nut and washers.

Note: the B+ bolt and the positive heatsink retaining screw are
fitted with mica insulating washers.
These must be discarded and replaced with new washers and
heatsink compound.

6D3-14  STARTING AND CHARGING SYSTEM

7. To remove the pulley, mount an 8mm Allen key in the vice

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

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

onto the Allen ken, loosen the nut and remove the pulley.

Note: the pulley has an integral boss which locks up against
the bearing,
therefore no thrust collar is provided.

8. Removing the rotor assembly. Remove the four retaining

screws from the drive end housing, withdraw the rotor

complete with the bearing.

Note: the rotor must not be pressed from the drive end housing
using a press as the bearing retaining plate and drive end
housing will be damaged or distorted. Parts removed in this
way must be replaced if the integrity of the generator is to be
maintained.
9. Remove the drive end bearing from the rotor shaft using a

chuck type puler, take care not to distort the fan assembly

during this process.

10.Remove the slipring end bearing using the same meghod

as in 9.

Clean

Thoroughly clean all components except the rotor and stator
with an approved cleaning agent.  Ensure that all traced of oil
and dirt are removed. If an abrasive cleaner is used to remove
scale and paint from the housings take care not to abrade the
bearing and mounting spigot surfaces.  The rotor and stator
must be cleaned with compressed air only, the use of solvents
could cause damage to the insulating materials.

Inspection

1. Rectifier assembly

The followoing test equipment is required.
The recitifier assembly is not repairable and must be replaced
if a faulty diode is detected during inspection.

(a) Adiode tester where the  DC output at the test probes does

not exceed 14 volts or in the case of AC testers 12 volts

RMS. This is to ensue that when inspection rectifiers fitted

with zener power diodes the forward and reverse checks

are completer and are not masked by the diode turning on

due to the zener breakdown voltage.

(b) A zenere diode tester with a DC output in excess of 30

volts, the tester should also incorporate internal current

limiting set to 5 Ma. to prevent high currents during

inspection.

(c) Diodes can be destroyed during service due to high

temperature and overload, open circuits are usually a result

of excessive voltage.