Lexus ES300 (1997 year). Manual - part 448

I00343

A/C Control Assembly

MGCR

AC1

ACT

A14

10

A14

13

A14

2

L–Y

IM2

7

L–Y

L–W

1

1

1

1

2C

2K

5

9

1W

HEATER

B–Y

LG–R

16

5

A/C

ACT

ECM

MG CLT

4

2

2

From HTR Relay

Magnetic Clutch Relay

L–B

L–B

B–W

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

DI–569

721

1997 LEXUS ES300   (RM511U)

Compressor Circuit

CIRCUIT DESCRIPTION

The A/C control assembly outputs the magnetic clutch ON signal from terminal AC1 to the ECM. When the
ECM receives this signal, it sends a signal from terminal ACT and switches the A/C magnetic clutch relay
ON, thus turning on the A/C magnetic clutch.

WIRING DIAGRAM

DI0DJ–01

I00344

MGCR(+)

(–)

AC3027

1

3

2

5

3

2

5

1

DI–570

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

722

1997 LEXUS ES300   (RM511U)

INSPECTION PROCEDURE

1

Check voltage between terminal MGC of A/C control assembly connector and
body ground.

PREPARATION:
(a)

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

BO–79

).

(b)

Start the engine and push AUTO switch.

CHECK:
Check voltage between terminal MGC of A/C control assembly
connector and body ground when magnetic clutch is ON and
OFF by A/C switch.
OK:

A/C switch

Voltage

ON

Below 1 V

OFF

10 – 14 V

NG

Go to step 5.

OK

2

Check magnetic clutch relay.

PREPARATION:
Remove magnetic clutch relay from R/B No.5.
CHECK:
Check continuity between each pair of terminals shown below
of magnetic clutch relay.
OK:

Tester connection

Specified condition

1 – 2

62.5 – 90.9 

Ω

3 – 5

No continuity

PREPARATION:
Apply battey positive (+) voltage between terminals 1 and 2.
CHECK:
Check continuity between terminals 3 and 5.
OK:

There is continuity.

NG

Replace magnetic clutch relay.

OK

N01150

I00340

AC1(+)

(–)

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

DI–571

723

1997 LEXUS ES300   (RM511U)

3

Check A/C magnetic clutch.

PREPARATION:
Disconnect magnetic clutch connector.
CHECK:
Connect positive (+) lead connected to battery to magnetic
clutch connector terminal 4.
OK:

Magnetic clutch is energized.

NG

Repair A/C magnetic clutch.

OK

4

Check harness and connector between magnetic clutch relay and A/C compers-
sor, A/C compressor and body ground (See page 

IN–27

).

NG

Repair or replace harness or connector.

OK

Proceed to next circuit inspeciton shown on
matrix chart (See page 

DI–535

).

5

Check voltage between terminal AC1 of A/C control assembly connector side
and body ground.

PREPARATION:
(a)

Disconnect A/C control connector.

(b)

Ignition switch ON.

CHECK:
Check voltage between terminal AC1 of A/C control assembly
harness side connector.
OK:

Voltage: 10 – 14 V

NG

Check and replace ECM.

Ok

I00341

AC1(+)

(–)

I00342

ACT(+)

(–)

DI–572

–

DIAGNOSTICS

AIR CONDITIONING SYSTEM

724

1997 LEXUS ES300   (RM511U)

6

Check voltage between terminal AC1 of A/C control assembly connector and
body ground.

PREPARATION:
(a)

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

BO–79

).

(b)

Start the engine and push AUTO switch.

CHECK:
Check the voltage between terminal AC1 of A/C control assem-
bly connector and body ground when magnetic clutch is ON
and OFF by A/C switch.
OK:

Magnetic clutch

Voltage

ON

Below 1 V

OFF

10 – 14 V

NG

Check and replace A/C control assembly.

OK

7

Check voltage between terminal ACT of A/C control assembly and body ground.

PREPARATION:
(a)

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

BO–79

).

(b)

Start the engine and push AUTO switch.

CHECK:
Check the voltage between terminal ACT of A/C control assem-
bly and body ground.
OK:

A/C switch

Voltage

ON

10 – 14 V

OFF

Below 1.5 V

NG

Check and replace ECM.

OK