Lexus ES300 (1997 year). Manual — part 660

234

AUTOMATIC AIR CONDITIONING

1. HEATER BLOWER MOTOR OPERATION

CURRENT IS APPLIED AT ALL TIMES THROUGH HTR FUSE TO TERMINAL 1 OF THE HTR RELAY. WHEN THE
IGNITION SW IS TURNED ON, CURRENT FLOWS THROUGH THE HEATER FUSE TO TERMINAL 5 OF THE HTR RELAY

TERMINAL 3

TERMINAL HR OF THE A/C CONTROL ASSEMBLY. AT THE SAME TIME, CURRENT ALSO FLOWS

FROM HEATER FUSE TO TERMINAL IG+ OF THE A/C CONTROL ASSEMBLY.

∗

LOW SPEED OPERATION
WHEN THE BLOWER SW (A/C CONTROL ASSEMBLY) IS PUSHED TO LOW SPEED POSITION, THE CURRENT TO
TERMINAL HR OF THE A/C CONTROL ASSEMBLY FLOWS TO TERMINAL GND OF THE A/C CONTROL ASSEMBLY

GROUND AND TURNS THE HTR RELAY ON. AS A RESULT, THE CURRENT TO TERMINAL 1 OF THE HTR RELAY
FLOWS TO TERMINAL 2 OF THE RELAY

TERMINAL 2 OF THE BLOWER MOTOR TERMINAL 1

TERMIANL 1 OF

THE BLOWER RESISTOR

TERMINAL 2

GROUND AND CAUSES THE BLOWER MOTOR TO ROTATE AT LOW

SPEED.

∗

HIGH SPEED OPERATION
WHEN THE BLOWER SW (A/C CONTROL ASSEMBLY) IS PUSHED TO HIGH SPEED POSITION, THE CURRENT TO
TERMINAL HR OF THE A/C CONTROL ASSEMBLY FLOWS TO TERMINAL GND OF THE A/C CONTROL ASSEMBLY

GROUND AND TURNS THE HTR RELAY ON. AS A RESULT, THE CURRENT TO TERMIANL 1 OF THE HTR RELAY
FLOWS TO TERMINAL 2

TERMINAL 2 OF THE BLOWER MOTOR TERMINAL 1

TERMINAL 4 OF THE A/C

BLOWER MOTOR LINEAR CONTROLLER

TERMINAL 2

TERMINAL BLW OF THE A/C CONTROL ASSEMBLY

(WHICH IS ACTIVATED WHEN THE BLOWER SW IS PUSHED TO HIGH SPEED POSITION)

TERMINAL GND

GROUND WITHOUT PASSING THROUGH THE BLOWER RESISTOR, CAUSING THE BLOWER MOTOR TO ROTATE AT
HIGH SPEED.

2. AIR INLET CONTROL SERVO MOTOR OPERATION

(SWITCHING FROM FRESH TO RECIRC)
WITH THE IGNITION SW TURNED ON, THE CURRENT FLOWS FROM HEATER FUSE TO TERMINAL IG+ OF THE A/C
CONTROL ASSEMBLY

TERMINAL AIR

TERMINAL 7 OF THE AIR INLET CONTROL SERVO MOTOR TERMINAL 6

TERMINAL AIF OF THE A/C CONTROL ASSEMBLY

TERMINAL GND

GROUND. THE MOTOR ROTATES AND

THE DAMPER MOVES TO THE RECIRC SIDE. WHEN THE DAMPER OPERATES WITH THE A/C SW AT RECIRC
POSITION, THE DAMPER POSITION SIGNAL IS INPUT FROM TERMINAL 5 OF THE SERVO MOTOR TO TERMINAL TPI
OF THE ECU (BUILT INTO THE A/C CONTROL ASSEMBLY). AS A RESULT, CURRENT TO THE SERVO MOTOR CIRCUIT
IS CUT OFF BY THE ECU, SO THE DAMPER STOPS AT THAT POSITION.
(SWITCHING FROM RECIRC TO FRESH)
WITH THE IGNITION SW TURNED ON, WHEN THE RECIRC/FRESH SW IS SWITCHED TO THE FRESH SIDE, THE
CURRENT FLOWS FROM TERMINAL IG+ OF THE A/C CONTROL ASSEMBLY

TERMINAL AIF

TERMINAL 6 OF

THE AIR INLET CONTROL SERVO MOTOR

TERMINAL 7

TERMINAL AIR OF THE A/C CONTROL ASSEMBLY

TERMINAL GND

GROUND, THE MOTOR ROTATES AND THE DAMPER STOPS AT THAT POSITION.

SYSTEM OUTLINE

235

3. AIR VENT MODE CONTROL SERVO MOTOR OPERATION

WHEN THE IGNITION SW TURNED ON, THE CURRENT FLOWS FROM HEATER FUSE TO TERMINAL IG+ OF THE A/C
CONTROL ASSEMBLY.
(SWITCHING FROM DEF TO FACE)
THE CURRENT FLOWS FROM TERMINAL FACE OF THE A/C CONTROL ASSEMBLY

TERMINAL 4 OF THE AIR VENT

MODE CONTROL SERVO MOTOR

TERMINAL 8

TERMINAL DEF OF THE A/C CONTROL ASSEMBLY

TERMINAL GND

GROUND. THE MOTOR ROTATES AND THE DAMPER MOVES TO THE FACE SIDE. WHEN TE

DAMPER OPERATES WITH THE A/C SW AT FACE POSITION, THE DAMPER POSITION SIGNAL IS INPUT FROM
TERMINAL 8 OF THE SERVO MOTOR TO THE TERMINAL DEF OF THE ECU (BUILT INTO THE A/C CONTROL
ASSEMBLY). AS A RESULT, CURRENT TO THE SERVO MOTOR CIRCUIT IS CUT OFF BY THE ECU, SO THE DAMPER
STOPS AT THAT POSITION.
(SWITCHING FROM FACE TO DEF)
THE CURRENT FLOWS FROM TERMINAL DEF OF THE A/C CONTROL ASSEMBLY

TERMINAL 8 OF THE AIR VENT

CONTROL SERVO MOTOR

TERMINAL

4 TERMINAL FACE OF THE A/C CONTROL ASSEMBLY

TERMINAL

GND

GROUND, THE MOTOR ROTATES AND THE DAMPER STOPS AT THAT POSITION.

4. AIR MIX CONTROL SERVO MOTOR OPERATION

WHEN THE TEMPERATURE CONTROL SW (A/C CONTROL ASSEMBLY) IS TURNED TO THE “COOL” SIDE THE
CURRENT FLOWS FROM TERMINAL AMC OF THE A/C CONTROL ASSEMBLY

TERMINAL 1 OF THE AIR MIX

CONTROL SERVO MOTOR

MOTOR

TERMINAL 2

TERMINAL AMH OF THE A/C CONTROL ASSEMBLY

GROUND AND THE MOTOR ROTATES. THE DAMPER OPENING ANGLE AT THIS TIME IS INPUT FROM TERMINAL 3 OF
THE SERVO MOTOR TO TERMINAL TP OF THE A/C CONTROL ASSEMBLY. THIS IS USED TO DETERMINE THE
DAMPER STOP POSITION AND MAINTAIN THE SET TEMPERATURE.
WHEN THE TEMPERATURE CONTROL SW (A/C CONTROL ASSEMBLY) IS TURNED TO THE “HOT” SIDE, THE
CURRENT FLOWS FROM SERVO MOTOR

TERMINAL AMH OF THE A/C CONTROL ASSEMBLY

TERMINAL 2 OF

THE AIR MIX CONTROL SERVO MOTOR

MOTOR

TERMINAL 1

TERMINAL AMC OF THE A/C CONTROL

ASSEMBLY, ROTATING THE MOTOR IN REVERSE AND SWITCHING THE DAMPER FROM “COOL” TO “HOT” SIDE.

5. AIR CONDITIONING OPERATION

THE A/C CONTROL ASSEMBLY RECEIVES VARIOUS SIGNALS, I.E., THE ENGINE RPM FROM THE ENGINE CONTROL
MODULE, OUT SIDE AIR TEMPERATURE SIGNAL FROM THE A/C AMBIENT TEMP. SENSOR, COOLANT
TEMPERATURE FROM THE ENGINE CONTROL MODULE AND THE LOCK SIGNAL FROM THE A/C COMPRESSOR,
ETC. WHEN THE ENGINE IS STARTED AND THE A/C SW (A/C CONTROL ASSEMBLY) IS ON, A SIGNAL IS INPUT TO
THE ECU. (BUILT IN THE A/C CONTROL ASSEMBLY).
AS A RESULT, THE GROUND CIRCUIT IN A/C CONTROL ASSEMBLY IS CLOSED AND CURRENT FLOWS FROM
HEATER FUSE TO TERMINAL 1 OF THE MG CLT RELAY

TERMINAL 2

TERMINAL MGCR OF THE A/C CONTROL

ASSEMBLY

TERMINAL GND

GROUND, TURNING THE MG CLT RELAY ON, SO THAT THE MAGNETIC CLUTCH IS

ON AND THE A/C COMPRESSOR OPERATES.
AT THE SAME TIME, THE ENGINE CONTROL MODULE DETECTS THE MAGNETIC CLUTCH IS ON AND THE A/C
COMPRESSOR OPERATES. IF THE A/C CONTROL ASSEMBLY DETECTS THE FOLLOWING CONDITIONS, IT STOPS
THE AIR CONDITIONING:

EVAPORATOR OUTLET AIR IS TOO LOW.

THERE IS A MARKED DIFFERENCE BETWEEN THE COMPRESSOR SPEED AND THE ENGINE SPEED.

THE REFRGIRANT PRESSURE IS ABNORMALLY HIGH OR ABNORMALLY LOW.

THE ENGINE SPEED IS TOO LOW.

RAPID ACCELERATION OCCURS.

2

3

4

1

5

10A
HEATER

FROM POWER SOURCE SYSTEM (SEE PAGE 56)

2

1

II

IBLE

K BLOCK

10A
ECU–B

L–

B

HTR
RELAY

A/C BLOWER MOTOR
LINEAR CONTROLLER

A13

1

1

1

1

1

EC

2

3

1

5

MG CLT
RELAY

1

1

1

1

I 4

I 4

E 3

IH1

2

M

2

1

EB1

1

IH1

1

I 3

IH1

5

B

3

L–B

L–B

L–R

L–R

B–Y

B–W

B–W

A

B

A

A

4

2

Y–W

L–B

W–B

W–B

W–B

W–R

JUNCTION
CONNECTOR

J 3

L–

B

L–B

L–

B

W–

W–

R

L–B

L–W

L–W

B–W

L–

R

L–

W

W–

B

L–

R

B–

W

B–

W

Y–

W

W–

B

L–W

1

W–

B

W–

B

W–

B

W–

B

L–B

W–

B

W

–

B

W–B

W–B

JUNCTION
CONNECTOR

J15

BLOWER MOTOR

B 2

W–B

BL

O

W

ER

R

E

S

IS

T

O

R

B 3

B–W

B

B

B

B

A

B

JUNCTION
CONNECTOR

B

J20

, J21

A

1W

2

1R

3

2J

7

R

FUS
LIN

50A

H

T

R

1

F10

2K

5

2C

9

1W

3

1V

10

236

AUTOMATIC AIR CONDITIONING

A/C CONTROL ASSEMBLY

B

A14

, A15

A

AIR INLET CONTROL
SERVO MOTOR

A26

L–O

B–

L

L–

R

L

L–

W

AIR VENT MODE

A28

IM3

12

IM2

7

A

20

A

19

A

18

A

17

A

4

B

7

A

6

B

9

B

16

A

3

A

10

B

2

A

26

A

13

L–

O

B–

L

L–

R

L

L–

W

P–

L

L–

Y

L–B

L–

B

L–

B

W–

B

W–

L

L–

W

L–Y

L–B

W–

R

IM2

9

L–W

L–W

B–W

Y–W

W–B

L–B

W–B

W–B

L–B

W–R

W–B

W–B

W–

R

W

–

L

W–

L

D

D

L–

Y

3

B–

W

B–

W

Y–

W

EB2

2

B

IG+

MGCR

HR

LOCK

BLW

PSW

AIF

TPI

FACE

B/L

FOOT

F/D

DEF

A

15

V–

W

SPD

T

O

SP

EED

O

M

ET

ER

[C

O

M

B

.

ME

T

E

R

]

A

7

A

23

A

25

B–R

Y–G

W–R

L–B

R

L

FROM RHEOSTAT

FROM DEFOGGER RELAY

RDFG

TC

AIR

IH1

6

1

W–R

L

1

4

A/C DUAL
PRESSURE
SW

A 4

2

4

1

5

6

A 3

A/

C

M

A

G

N

ET

IC

C

L

U

T

C

H

AN

D

L

O

C

K

SEN

SO

R

IO

DE

(

A/

C

)

2

2

3

7

M

M

8

7

6

5

4

2

1

DEF

F/D

FOOT

B/L

FACE

IG

GND

CONTROL SERVO MOTOR

A

B

CONTROL
CIRCUIT

237