Lexus ES300 (1997 year). Manual - part 450

I00373

GND(–)

LOCK

I00348

HEATER

Instrument Panel J/B

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

DI–577

729

1997 LEXUS ES300   (RM511U)

2

Check continuity between terminal GND of A/C control assembly and body
ground.

CHECK:
Measure resistance between terminal GND of A/C control as-
sembly and body ground.
OK:

Resistance: Below 1 

Ω

NG

Repair or replace harness or connector.

OK

3

Check HTR fuse.

PREPARATION:
Remove HEATER fuse in instrument panel J/B.
CHECK:
Check continuity of HEATR fuse.
OK:

There is continuity.

OK

Check for shot in all the harness and compo-
nents connected to the HEATER fuse
(See page 

DI–576

).

OK

Check and repair harness and connector between A/C control assembly and battery.

I00351

A/C Control Assembly

+B

13

A13

J3

W–B

W–B

1V

10

3

1W

W–B

2J

7

1

2A

ECU–B

B

F8

F6

1

1

MAIN FL

Battery

B

B

I00352

+B(+)

(–)

DI–578

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

730

1997 LEXUS ES300   (RM511U)

Back Up Power Source Circuit

CIRCUIT DESCRIPTION

This is the back–up power source for the A/C control assembly. Power is supplied even when the ignition
switch is off and is used for DTC memory, etc..

WIRING DIAGRAM

INSPECTION PROCEDURE

1

Check voltage between terminal +B fo A/C control assembly connector and body
ground.

PREPARATION:
(a)

Remove front ash receplacle (See page 

BO–79

).

(b)

Remove A/C control assembly with connectors still con-
nected (See page 

BO–79

).

CHECK:
Measure voltage between termimal +B of A/C control assembly
connector and body ground.
OK:

Voltage: 10 – 14 V

OK

Proceed to nect circuit inspection shown on
matrix chart (See page 

DI–535

).

NG

DI0DM–01

I00349

Engine Room J/B

ECU–B

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

DI–579

731

1997 LEXUS ES300   (RM511U)

2

Check ECU–B fuse.

PREPARATION:
Remove ECU–B fuse from engine room J/B.
CHECK:
Check continuity of ECU–B fuse.
OK:

There is continuity.

NG

Check for short in all the harness and compo-
nents connected to the ECU–B fuse
(See page 

DI–578

).

OK

Check and repair harness and connector between A/C control assembly and battery.

I00350

A/C Control Assembly

HR

A13

10

L–W

EB2

2

L–W

From MG CLT Relay

From HEATER Fuse

1

1

1

1

1

HTR Main Relay

W–B

Blower Motor

L–R

EC

DI–580

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

732

1997 LEXUS ES300   (RM511U)

Heater Main Relay Circuit

CIRCUIT DESCRIPTION

The heater main relay is switched on by signals from the A/C control assembly. It supplies power to the blow-
er motor.

WIRING DIAGRAM

DI0DN–01