Isuzu N-Series. Manual - part 634

ENGINE ELECTRICAL 6D-29

4. Check for continuity between slip ring and rotor

core or slip ring and rotor shaft.
In case of continuity, replace the rotor assembly.

Rear Ball Bearing
Check to see if the ball bearing rotates smoothly with no
noises.
When it does not rotate smoothly or any noises are
heard, replace it with a new one.
When installing the bearing, press it in with the stopper
ring turned to the spline side, while pushing the bearing
inner ring.

Stator Coil

1. Check for continuity between respective phases.

In case of no continuity, replace the stator.

Legend

1. Slip ring
2. Tester

Legend

1. Slip ring
2. Tester

N6A3535E

N6A3536E

Bearing press-in measurement: L

mm (in)

Standard

41.8 — 42.0 (1.64 — 1.65)

Legend

1. Stopper ring
2. Ball bearing
3. Spline

Legend

1. Tester
2. Lead wire

N6A3537E

N6A3538E

6D-30 ENGINE ELECTRICAL

2. Check for continuity across one of the stator coils

and stator core. If a continuity exists, replace the
coil.

Diode

1. Check for continuity across the terminal (example:

across BAT and U). If a continuity exists, the diode
is in satisfactory condition. If no continuity exists
the diode is defective.

2. Make a test with the polarities reversed. If no con-

tinuity exists, the diode is in satisfactory condition.
If a continuity exists at any point, the diode is de-
fective and should be replaced.
Auxiliary diodes are not provided with the terminal
and continuity test should be made across the ter-
minals of the conventional diodes.

Brush
Measure length of brushes.
Brush length (L)

Brushes are provided with a line which indicates the limit
of usage.

Legend

1. Tester
2. Lead wire

N6A3539E

N6A3540E

Legend

1. Tester

- side diode check

Across terminals

BAT (Positive side (+) diodes)

Tester 

pin

Positive side

Negative side

U.V.W

Positive 

side

No continuity

Negative 

side

Continuity

+ side diode check

Across terminals

E (Negative side (

−) diodes)

Tester 

pin

Positive side

Negative side

U.V.W

Positive 

side

Continuity

Negative 

side

No continuity

mm (in)

Standard

Limit

20 (0.79)

6 (0.24)

N6A3541E

ENGINE ELECTRICAL 6D-31

IC Regulator
Measuring instruments is necessary.
Take the following measurements with the instruments
connected as shown in the illustration.

Take measurement with ‘S’ terminal disconnected.

• Measurement the voltage across the E — F while

varying resistance gradually from zero using vari-
able resistor.
Then check that voltage increases from 2V to 10 —
13.
If increase in voltage is interrupted at any point, re-
place the regulator.

• V4 Measure the voltage across the intermediate

tap on variable resistor and ‘E’ terminal without ac-
tuating the variable resistor.

If measured value deviates from the standard, re-
place the regulator.

Check the following with the instrument connected as il-
lustrated.
Measure the voltage across the terminals B and E by
gradually increasing voltage with variable resistor RV.

Legend

1. Wear limit

V1 Voltage at Battery1

V

Standard

10 — 13

V2 Voltage across F — E

V

Standard

Limit

2 or less

2 or more

V3 Measure the voltage at Battery1 — Battery2.

V

Standard

20 — 26

N6A3533E

V

Standard voltage at 20

°C (68°F)

14.0 — 14.9

N6A3542E

N6A3543E

6D-32 ENGINE ELECTRICAL

Check to see if voltage increases from lower than 2V to
range from 10 to 13 volts.
If the voltage does not vary, the regulator is defective
and should be replaced.
Check the voltage across the intermediate tap of the
variable resistor and terminal E without actuating the
variable resistor.

If measured voltage deviates from the standard value,
replace the regulator.
Vacuum Pump
Visual Check

• Inspect the following parts for wear, damage or

other abnormal conditions.

Disassembly of Vacuum Pump

• For the center plate, rotor and vane in the men-

tioned. 

Housing

• Measure the inside diameter of housing and place

if it exceed the standard.

Vane
Measure the length of vanes

Check Valve

1. Apply a light pressure onto the “B” side of valve

with a screwdriver and check that valve operates
smoothly.

2. Apply compressed air 100 — 500 kPa (1 — 5 kg/

cm

2

/14.5 — 72.5 psi) onto “A” side of valve and

check if there is air leak.

V

Standard voltage at 20

°C (68°F)

14.5 — 16.9

Legend

1. Center plate
2. Vane
3. Rotor
4. Housing

mm (in)

Standard

57.0 — 57.1 (2.244 — 2.248)

N6A3544E

mm (in)

Standard

12.5 — 13.5 (0.492 — 0.531)

Legend

1. Compressed air
2. Push

N6A3545E

N6A3546E