Isuzu KB P190. Manual — part 1356

8A-486 ELECTRICAL-BODY AND CHASSIS

TROUBLE SHOOTING

Rear defogger inoperative

Checkpoint

Trouble

Cause

Countermeasure

Reinstall or replace the fuse
No. C7 (10A) and 9

B56

Poor fuse contact or blown

NG

Reinstall or replace the fuse

C18 (20A)

C18 (20A, Fuse box)

Poor fuse contact or blown

Replace the rear defogger

switch

Rear defogger switch function

Switch malfunction

NG

NG

OK

OK

OK

Fuse No. C3 (10A, Fuse box)
and 9

B56

Replace the rear defogger

relay

Relay malfunction

NG

Continued on the next page

Rear defogger relay function

Repair grounding point contact

Grounding point

C2

Poor grounding point contact

NG

OK

Repair open circuit or poor
connector contact between
fuse No. C3 (10A) and 3

B7

, C18 (20A) and 1

B7

, 2

B7

(3

B55

) and

1

L4

, 4

B7

(3

B54

)

and 3

B46

or 1

B46

and

C2

Voltage between 1

L4

-

ground when the starter switch
and the rear defogger switch
are at on position (should be
battery voltage present)

Open circuit or poor connector

contact

NG

OK

ELECTRICAL-BODY AND CHASSIS 8A-487

Checkpoint

Trouble

Cause

Countermeasure

OK

Repair open circuit or

connector contact between 1

L7

and

C2

Open circuit or poor connector

contact

NG

Continued from the previous page

Continuity between 1

L7

and

C2

Repair heat wire

Continuity between rear

defogger terminals

Broken heat wire of rear

defogger

NG

OK

8A-488 ELECTRICAL-BODY AND CHASSIS

REMOVAL AND INSTALLATION

1

RTW77ASH000201

REAR DEFOGGER SWITCH

Removal

1. Instrument Panel Cluster Assembly

• Refer to Section 10 “BODY” for center cluster panel

assembly removal steps.

2. Rear Defogger Switch (With HVAC control unit) (1)

Refer to Section 1 “HVAC” HVAC control unit assembly

removal steps.

Installation

Follow the removal procedure in the reverse order to install the
rear defogger switch.

ELECTRICAL-BODY AND CHASSIS 8A-489

INSPECTION AND REPAIR

Switch side

B57

REAR DEFOGGER SWITCH

Rear Defogger Switch Connections

Terminal No.

SW position

9 7 8

ON

OFF

B7

RTW78ASH002901

REAR DEFOGGER RELAY

Check continuity between the relay terminals.

2

-

1

. . . . . . No continuity

(When battery voltage is applied between

4

and

3

)

2

-

1

. . . . . . Continuity

INSPECTION OF REAR DEFOGGER HEAT

WIRE

• Heat wires are printed on the inner side of glass.

To clean, use a soft cloth and wipe horizontally along the

wires.

• Never use glass cleaner or equivalent.
• When measuring voltage, wind a piece of tin foil around the

tip of the negative probe and press the foil against the wire

with your finger as shown.

(1) Turn the ignition switch on.

(2) Turn the defogger switch on.

(3) Measure the voltage between the three points on the heat

wire and the (-) terminal with a voltmeter.

(4) Check that the voltage becomes smaller from

A

to

B

to

C

.

(5) If there is a place where the voltage suddenly changes to

0V, there is a broken wire between there and the power

side.

(6) Move the tester probe from the position where the voltage

changes to 0V toward the power side and find where the

voltage suddenly increases.