Lexus RX300 (MCU15). Service manual — part 148

BE0GH–13

I19126

Instrument Panel J/B
D SEAT HTR Fuse
D Engine Main Relay

Seat Heater Relay

Seat Back Heater

Seat Cushion Heater

LH Seat Heater Switch

RH Seat Heater Switch

–

BODY ELECTRICAL

SEAT HEATER SYSTEM

BE–139

LEXUS RX300 (RM785E)

SEAT HEATER SYSTEM

LOCATION

BE1YM–01

I19231

LH Side

RH Side

I19232

6

3

LH Side

RH Side

6

3

I19233

Wire Harness Side

LH Side

RH Side

I19132

Seat Back Side

Connector ”A”

Wire Harness

Side

Connector ”B”

BE–140

–

BODY ELECTRICAL

SEAT HEATER SYSTEM

LEXUS RX300 (RM785E)

INSPECTION

1.

INSPECT SEAT HEATER SWITCH CONTINUITY

Condition

Tester connection

Specified condition

OFF

–

No continuity

HI

2 – 4, 3 – 6

Continuity

LO

3 – 4

Continuity

Illumination circuit

1 – 5

Continuity

If continuity is not as specified, replace the switch or bulb.

2.

INSPECT SEAT HEATER SWITCH INDICATOR

(a)

Connect the positive (+) lead from the battery to terminal
3 and the negative (–) lead to terminal 6.

(b)

Push the switches ”HI” position, check that the indicator
of ”HI” position lights up.

(c)

Push the switches ”LO” position, check that the indicator
of ”LO” position lights up.

If operation is not as specified, replace the switch and inspect
the circuits connected to other parts.

3.

INSPECT SEAT HEATER SWITCH CIRCUIT

Disconnect the switch connector and inspect the connector on
the wire harness side.

Tester connection

Condition

Specified condition

6 – Ground

Constant

Continuity

4

Ground

Ignition switch position LOCK or ACC

No voltage

4 – Ground

Ignition switch position ON

Battery positive voltage

1

Ground

Light control switch OFF

No voltage

1 – Ground

Light control switch TAIL or HEAD

Battery positive voltage

If the circuit is not as specified, inspect the circuits connected
to other parts.

4.

INSPECT SEAT HEATER CUSHION CONTINUITY

(a)

Disconnect the seat back heater from the seat cushion
heater.

(b)

Heat the thermostat with a light.

(c)

Inspect the seat cushion heater continuity between termi-
nals, as shown.

I19127

Connector ”A”
(To Vehicle Wireharness)

Connector ”B”
(To Seat Back Heater)

I19128

Wire Harness Side

–

BODY ELECTRICAL

SEAT HEATER SYSTEM

BE–141

LEXUS RX300 (RM785E)

Tester connection

Condition

Specified condition

A1 – B3

Constant

Continuity

A2 – B4, A3 – B2

Seat heater temp. below 25

- 35 °C (77 – 95 °F) Continuity

A3 – B2

Seat heater temp. 46 – 54

°C (115 – 129 °F) or

more

No continuity

A2 – B1

Seat heater temp. 36 – 44

°C (97 – 111 °F) or

more

No continuity

If continuity is not as specified, replace the seat cushion hearer.

5.

INSPECT SEAT HEATER CUSHION CONTINUITY

Inspect the seat heater inner cushion and front cushion continu-
ity between terminals, as shown.

Tester connection

Condition

Specified condition

A1 – B3, A2 – B1

Seat heater temp. below 25

°C (77 °F)

Continuity

If continuity is not as specified, replace the seat cushion heater.

6.

INSPECT SEAT BACK CONTINUITY

Inspect the seat back continuity between terminals, as shown.

Tester connection

Condition

Specified condition

1 – 3, 2 – 3

Seat heater temp. below 25

°C (77 °F)

Continuity

If continuity is not as specified, replace the seat back heater.

The radio wave bands used in radio broadcasting are as follows:

Frequency

Designation

Radio wave

Modulation method

LF: Low frequency MF: Medium Frequency HF: High Frequency VHF: Very High Frequency

Amplitude modulation

Frequency modulation

30 kHz

300 kHz

3 MHz

30 MHz

300 MHz

LF

MF

HF

VHF

AM

FM

BE1VH–02

BE2818

FM (Stereo)

FM (Monaural)

AM

BE2819

Fading

Ionosphere

BE–142

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BODY ELECTRICAL

AUDIO SYSTEM (Europe)

LEXUS RX300 (RM785E)

AUDIO SYSTEM (Europe)

DESCRIPTION

1.

RADIO WAVE BAND

2.

SERVICE AREA

There are great differences in the size of the service area for AM
and FM monaural. Sometimes FM stereo broadcasts cannot be
received even through AM comes in very clearly.
Not only does FM stereo have the smallest service area, but it
also picks up static and other types of interference (”noise”)
easily.

3.

RECEPTION PROBLEMS

Besides the problem of static, there are also the problems
called ”fading”, ”multipath” and ”fade out”. These problems are
caused not by electrical noise but by the nature of the radio
waves themselves.

S

Fading
Besides electrical interference, AM broadcasts are
also susceptible to other types of interference, es-
pecially at night. This is because AM radio waves
bounce off the ionosphere at night. These radio
waves then interfere with the signals from the same
transmitter that reach the vehicle’s antenna directly.
This type of interference is called ”fading”.