Isuzu N-Series. Manual - part 1149

8-308 CAB AND CHASSIS ELECTRICAL

3-3. Needle Overshoots (or Goes Up to the “H” Range)

• DISCONNECT THE CONNECTOR OF THE THERMO

UNIT

• WHEN THE STARTER SW IS TURNED ON, DOES

THE POINTER REACH TO THE "H" RANGE?

• IS THERE A SHORT CIRCUIT BETWEEN THE

THERMO UNIT AND THE COOLANT
TEMPERATURE GAUGE?

REPLACE THE THERMO UNIT

• IS THE PRINTED CIRCUIT OF THE METER

ASSEMBLY GROUNDED SECURELY?

REPAIR A SHORT CIRCUIT

YES

YES

NO

YES

NO

NO

REPAIR OR REPLACE THE PRINTED CIRCUIT BOARD

CHECK THE COOLANT TEMPERATURE GAUGE AND
REPLACE IT IF FOUND ABNORMAL

N8A0310E

CAB AND CHASSIS ELECTRICAL 8-309

4. Fuel Gauge
4-1. Fuel Gauge Needle Does Not Move

• IS THE CONNECTOR OF THE FUEL TANK UNIT  J-28

CONNECTED SECURELY?

• DISCONNECT THE CONNECTOR OF THE FUEL

TANK UNIT 

• CONNECT A 3.4W BULB BETWEEN THE HARNESS

SIDE CONNECTOR 1  J-28  AND THE GROUND OF
THE FUEL TANK UNIT

• WHEN THE STARTER SW IS TURNED ON, DOES THE

FUEL GAUGE NEEDLE FLUCTUATE AFTER ABOUT 90
SECONDS?

• IS THERE CONTINUITY BETWEEN THE FUEL

TANK UNIT CONNECTOR TERMINALS 1  J-28
AND 3  J-28  ?

YES

NO

REPLACE THE FUEL
TANK UNIT

REPAIR A POOR
CONNECTION AT THE
CONNECTORS OR AN
OPEN CIRCUIT
BETWEEN THE FUEL
TANK UNIT AND THE
METER

YES

YES

NO

YES

• IS THERE A BROKEN

WIRE IN THE PRINTED
CIRCUIT OF THE
METER ASSEMBLY?

YES

NO

CHECK THE FUEL
METER, AND REPLACE IT
IF NECESSARY

REPLACE THE PRINTED
CIRCUIT BOARD

REPAIR A POOR
CONNECTION AT THE
CONNECTORS OR AN
OPEN CIRCUIT IN THE
CIRCUIT

NO

• IS THE CIRCUIT BETWEEN THE FUEL GAUGE AND

THE FUEL TANK UNIT NORMAL?

NO

CONNECT THE CONNECTOR SECURELY

N8A0311E

8-310 CAB AND CHASSIS ELECTRICAL

4-2. Even when The Tank Is Filled Up with Fuel, The Needle Does Not Reach “F”

• WHEN INSERTING AND PULLING OUT THE

CONNECTOR  J-28  OF THE FUEL TANK UNIT
SEVERAL TIMES, DOES THE POINTER OF THE FUEL
GAUGE STAY AT THE SAME POSITION?

• DISCONNECT THE CONNECTOR OF THE FUEL TANK

UNIT 

• CONNECT THE FUEL TANK UNIT HARNESS SIDE

CONNECTOR 1  J-28  AND 3  J-28  WITH A LEAD
WIRE

• WHEN THE STARTER SW IS TURNED ON, DOES THE

NEEDLE OVERSHOOT TO "F" AFTER ABOUT 5
MINUTES?

• IS THERE A BROKEN CIRCUIT IN THE PRINTED

CIRCUIT OF THE METER ASSEMBLY?

YES

NO

REPLACE THE PRINTED
CIRCUIT BOARD

CHECK THE FUEL
GAUGE AND REPLACE
IT IF FOUND
ABNORMAL

YES

YES

NO

YES

• IS THE RESISTANCE

VALUE OF THE FUEL
TANK UNIT NORMAL?

NO

REPLACE THE FUEL
TANK UNIT

• REMOVE THE FUEL TANK UNIT

• DOES THE FLOAT ARM OPERATE SMOOTHLY?

NO

REPAIR A POOR CONNECTION AT THE CONNECTOR
OF THE FUEL TANK UNIT

N8A0312E

CAB AND CHASSIS ELECTRICAL 8-311

4-3. When The Tank Is Not Full of Fuel, The Needle Overshoots (or Goes Up to “F”)

• DISCONNECT THE CONNECTOR OF THE FUEL TANK

UNIT

• WHEN THE STARTER SW IS TURNED ON, DOES THE

NEEDLE STILL POINT TO "F"?

• IS THE CIRCUIT BETWEEN THE FUEL TANK UNIT

AND THE FUEL METER NORMAL?

YES

NO

NO

REPAIR A SHORT
CIRCUIT IN THE
CIRCUIT

REPAIR OR REPLACE
THE PRINTED CIRCUIT
BOARD

CHECK THE FUEL
GAUGE, AND REPLACE
IT IF NECESSARY

• IS THE PRINTED

CIRCUIT OF THE
METER ASSEMBLY
GROUNDED
SECURELY?

• ARE THE RESISTANCE VALUES OF THE

FUEL TANK UNIT AT "E" AND "F" POINTS
NORMAL?

YES

YES

YES

NO

REPLACE THE FUEL TANK UNIT

NO

• REMOVE THE FUEL TANK UNIT

• DOES THE FLOAT ARM OPERATE SMOOTHLY?

N8A0313E