Lexus SC300 / Lexus SC400. Manual - part 213

(c)  Turn the defogger switch ON and check that the test bulb and

indicator light turn ON, then turn OFF after about 15 minutes.

If operation is not as specified, replace the air conditioner control
panel assembly.

(Defogger Relay)
INSPECTION OF DEFOGGER RELAY

INSPECT RELAY CONTINUITY AND OPERATION

If continuity is not as specified, replace the relay.

(Defogger Wires)

INSPECTION AND REPAIR OF
DEFOGGER WIRES

1. 

INSPECT DEFOGGER WIRES
NOTICE:

•

When cleaning the glass, use a soft, dry cloth, and wipe

the glass in the direction of the wire. Take care not to

damage the wires.

•

Do not use detergents or glass cleaners with abrasive

ingredients.

•

When measuring voltage, wind a piece of tin foil around

the top of the negative probe and press the foil against

the wire with your finger as shown.

(a)  Turn the ignition switch ON.
(b)  Turn the defogger switch ON.
(c)  Inspect the voltage at the center of each heat wire as

shown.

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Voltage

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Criteria

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Approx. 5 V

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Okay (No break in wire)

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Approx. 10 V or 0 V

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Broken wire

HINT: If there is approximately 10 volts, the wire is broken be-
tween the center of the wire and the positive (+) end. If there
is no voltage, the wire is broken between the center of the
wire and ground.

–

BODY ELECTRICAL SYSTEM

Defogger System

BE–53

(d)  Place the voltmeter positive (+) lead against the defogger

positive (+) terminal.

(e) Place 

the voltmeter negative (–) lead with the foil strip against

the heat wire at the positive (+) terminal end and slide it
toward the negative (–) terminal end.

(f)  The point where the voltmeter deflects from zero to several

volts is the place where the heat wire is broken.

HINT: IF the heat wire is not broken, the voltmeter indicates 0 volts
at the positive (+) end of the heat wire but gradually increases to
about 12 volts as the meter probe is moved to the other end.

2. 

REPAIR DEFOGGER WIRES
(a)  Clean the broken wire tips with a grease, wax and

silicone remover.

(b)  Place the masking tape along both sides of the wire to

be repaired.

(c)  Thoroughly mix the repair agent (Dupont paste No.

4817).

(d)  Using a fine tip brush, apply a small amount to the wire.

(e)  After a few minutes, remove the masking tape.

(f)  Allow the repair to stand at least 24 hours.

(Mirror Defogger)

REMOVAL AND INSTALLATION OF
MIRROR ASSEMBLY

(See Outside Rear View Mirror on Pub. No. RM260U2, page

BO–42

)

BE–54

–

BODY ELECTRICAL SYSTEM

Defogger System

INSPECTION OF MIRROR DEFOGGER

INSPECT MIRROR DEFOGGER
(a) Connect 

the positive (+) lead from the battery to terminal 7 (4)

and the negative (–) lead to terminal 8 (5).

(b)  Check that the mirror becomes warm.

HINT: It will take a short time for the mirror to become warm.
If the mirror does not become warm, replace the mirror as-
sembly.

( ): w/o Driving Position Memory

Troubleshooting

You will find the cause of trouble more easily using the table shown below. In this table, the number indicate
the order priority of the causes in trouble. Check each part in the order shown. If necessary, replace the parts.

 Refer to 1992 LEXUS SC300 Repair Manual (Pub. No. RM260U2)

See page

BE–4

, 

20

BE–4

, 

20

BE–4

, 

22

BE–172

BE–173

BE–173

BE–174

–

BODY ELECTRICAL SYSTEM

Defogger System

BE–55

(TAILLIGHT SYSTEM)
Description – Taillight System

The component parts of this system and their function are as shown in the following table.

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Parts Name

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Function

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Light Control Switch

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Grounds current from the taillight control relay via the integration relay, switching each relay
and supplying current to the appropriate bulbs accordance with the switch position.

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Taillight Control Relay

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Turned on by signals from the light control switch and supplies current to each bulb.

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Integration Relay

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Carries out ”Light Auto Turn–Off” of the headlights, fog lights and taillights and cuts off cur-
rent to the light control switch in accordance with signals from the GAUGE fuse and door
courtesy switch.

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Light Failure Sensor

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This sensor senses when a bulb in rear combination light is burnt out and lights up a warning
light.

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Integration Relay

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Integration Relay
(Daytime Running

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Refer to 

BE–30

.

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(

y

g

Light Relay: CANADA)

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PARTS LOCATION – Taillight System

–

BODY ELECTRICAL SYSTEM

Lighting System

BE–53