LEXUS SC400 1991 Service Repair Manual

226
AUTOMATIC AIR CONDITIONER
1. HEATER BLOWER MOTOR OPERATION
CURRENT IS APPLIED AT ALL TIMES THROUGH HEATER FUSE (60A) TO TERMINAL 5 OF HEATER RELAY. WHEN THE IGNITION SW IS
TURNED ON, CURRENT FLOWS THROUGH HEATER FUSE (10A) TO TERMINAL 1 OF HEATER RELAY " TERMINAL 3 " TERMINAL HR
OF A/C CONTROL ASSEMBLY. AT THE SAME TIME, CURRENT ALSO FLOWS FROM HEATER FUSE (10A) TO TERMINAL IG+ OF A/C
CONTROL ASSEMBLY AND TERMINAL 2 OF WATER VALVE VSV " TERMINAL 1 " TERMINAL WV OF 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 A/C
CONTROL ASSEMBLY FLOWS TO TERMINAL E OF A/C CONTROL ASSEMBLY " GROUND AND TURNS THE HEATER RELAY. AS A
RESULT, THE CURRENT TO TERMINAL 5 OF HEATER RELAY FLOWS TO TERMINAL 4 OF RELAY " TERMINAL 2 OF BLOWER
RESISTOR " TERMINAL 1 " GROUND AND CAUSES THE BLOWER MOTOR TO ROTATE AT LOW SPEED.
* MEDIUM (M1, M2, M3) AND HIGH SPEED OPERATION
WHEN THE BLOWER SW (A/C CONTROL ASSEMBLY) IS SELECTED TO MEDIUM (M1, M2, M3) OR HIGH POSITION, THE CURRENT TO
TERMINAL HR OF A/C CONTROL ASSEMBLY FLOWS TO TERMINAL E " GROUND AND TURNS THE HEATER RELAY ON. THEN, THE
CURRENT TO TERMINAL IG+ OF A/C CONTROL ASSEMBLY FLOWS TO TERMINAL BLR " TERMINAL (B)2 OF POWER TRANSISTOR
" TERMINAL (A)1 " GROUND. AS A RESULT, THE CURRENT TO TERMINAL 5 OF HEATER RELAY FLOWS TO TERMINAL 4 "
TERMINAL 2 OF BLOWER MOTOR " TERMINAL 1 " TERMINAL (A)2 OF POWER TRANSISTOR " TERMINAL (A)1 " GROUND AND
BLOWER MOTOR IS ROTATED AT SELECTED SPEED BY THE A/C CONTROL ASSEMBLY CONTROLLING THE CURRENT FLOW FROM
TERMINAL (B)2 OF POWER TRANSISTOR TO TERMINAL (B)1.
* AUTO FUNCTION
WHEN THE AUTO SW IN HEATER CONTROL SW (A/C CONTROL ASSEMBLY) IS SELECTED, THE CURRENT FLOW IS THE SAME AS
ABOVE MENTIONS, BUT THE A/C CONTROL ASSEMBLY DECIDES THE APPROPRIATE AIR FLOW VOLUME ACCORDING TO SET
TEMPERATURE AND THE INPUT SIGNALS FROM EACH SENSOR. BY CONTROLLING THE CURRENT FLOW\
FROM TERMINAL BLR OF
THE A/C CONTROL ASSEMBLY TO TERMINAL (B)2 OF POWER TRANSISTOR " TERMINAL (A)1 " GROUND , THE A/C CONTROL
ASSEMBLY CONTROLS THE BLOWER MOTOR STEPLESSLY.
2. OPERATION OF AIR INLET CONTROL SERVO MOTOR
(SWITCHING FROM FRESH TO RECIRC)
WITH IGNITION SW TURNED ON, THE CURRENT FLOWS FROM HEATER FUSE (10A) TO TERMINAL IG+ OF A/C CONTROL ASSEMBLY
" TERMINAL MREC " TERMINAL 6 OF AIR INLET CONTROL SERVO MOTOR " TERMINAL 2 " TERMINAL MFRS OF A/C CONTROL
ASSEMBLY " TERMINAL E " 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 IGNITION SW TURNED ON, WHEN THE RECIRC/FRESH SW IS SWITCHED TO THE FRESH SIDE, THE CURRENT FLOWS FROM
TERMINAL IG+ OF A/C CONTROL ASSEMBLY " TERMINAL MFRS " TERMINAL 2 OF AIR INLET CONTROL SERVO MOTOR "
TERMINAL 6 " TERMINAL MREC OF A/C CONTROL ASSEMBLY " TERMINAL E " GROUND , THE MOTOR ROTATES AND THE
DAMPER STOPS AT THAT POSITION.
3. OPERATION OF AIR VENT MODE CONTROL SERVO MOTOR
WITH IGNITION SW TURNED ON, THE CURRENT FLOWS FROM HEATER FUSE (10A) TO TERMINAL IG+ OF A/C CONTROL ASSEMBLY.
(SWITCHING FROM DEF TO FACE)
THE CURRENT FLOWS FROM TERMINAL MFACE OF A/C CONTROL ASSEMBLY " TERMINAL 4 OF AIR VENT CONTROL SERVO
MOTOR " TERMINAL 5 " TERMINAL MDEF OF A/C CONTROL ASSEMBLY " TERMINAL E " GROUND . THE MOTOR ROTATES AND
THE DAMPER MOVES TO THE FACE SIDE. WHEN THE DAMPER OPERATES WITH THE A/C SW AT FACE POSITION, THE DAMPER
POSITION SIGNAL IS INPUT FROM TERMINAL 1 OF THE SERVO MOTOR TO THE TERMINAL TPM 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 A/C CONTROL ASSEMBLY " TERMINAL 5 OF AIR VENT CONTROL SERVO MOTOR
" TERMINAL 4 " TERMINAL MFACE OF A/C CONTROL ASSEMBLY " TERMINAL E " GROUND , THE MOTOR ROTATES AND THE
DAMPER STOPS AT THAT POSITION.
SYSTEM OUTLINE
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4. OPERATION OF AIR MIX CONTROL SERVO MOTOR
WHEN THE TEMPERATURE SW IS TURNED TO THE ªCOOLº SIDE, THE CURRENT FLOWS FROM TERMINAL MC OF A/C CONTROL
ASSEMBLY " TERMINAL 4 OF AIR MIX CONTROL SERVO MOTOR " MOTOR " TERMINAL 5 " TERMINAL MH OF A/C CONTROL
ASSEMBLY " GROUND AND THE MOTOR ROTATES. THE DAMPER OPENING ANGLE AT THIS TIME IS INPUT FROM TERMINAL 1 OF
SERVO MOTOR TO TERMINAL TP OF A/C CONTROL ASSEMBLY, THIS IS USED TO DETERMINE THE DAMPER STOP POSITION AND
MAINTAIN THE SET TEMPERATURE.
WHEN THE TEMPERATURE CONTROL SW IS TURNED TO THE ªHOTº SIDE, THE CURRENT FLOWS FROM SERVO MOTOR "
TERMINAL MH OF A/C CONTROL ASSEMBLY " TERMINAL 5 OF AIR MIX CONTROL SERVO MOTOR " MOTOR " TERMINAL 1 "
TERMINAL MC OF A/C CONTROL ASSEMBLY, ROTATING THE MOTOR IN REVERSE AND SWITCHING THE DAMPER FROM ªCOOLº TO
ªHOTº SIDE.
5. AIR CONDITIONER OPERATION
THE A/C CONTROL ASSEMBLY RECEIVES VARIOUS SIGNALS, I.E., THE ENGINE RPM FROM THE IGNITER, OUTLET TEMPERATURE
SIGNAL FROM THE A/C THERMISTOR, COOLANT TEMPERATURE FROM THE WATER TEMP. SENSOR 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 (10A) TO
TERMINAL 2 OF MAGNETIC CLUTCH RELAY " TERMINAL 3 " TERMINAL ACMG OF ENGINE AND ECT ECU " TERMINAL E OF A/C
CONTROL ASSEMBLY " GROUND , TURNING THE MAGNETIC CLUTCH RELAY ON, SO THAT THE MAGNETIC CLUTCH IS ON AND THE
A/C COMPRESSOR OPERATES.
AT THE SAME TIME, THE ENGINE AND ECT ECU DETECTS THE MAGNETIC CLUTCH IS O\
N AND THE A/C COMPRESSOR OPERATES.
OPEN DIRECTION TO AVOID LOWERING THE ENGINE RPM DURING A/C OPERATING.
WHEN ANY OF THE FOLLOWING SIGNALS ARE INPUT TO THE A/C CONTROL ASSEMBLY, THE CONTROL ASSEMBLY OPERATES TO
TURN OFF THE AIR CONDITIONING.
* ENGINE HIGH TEMP. SIGNAL IS HIGH.
* COOLANT HIGH TEMP. SIGNAL IS HIGH.
* A SIGNAL THAT THE TEMPERATURE AT THE AIR OUTLET IS LOW.
* A SIGNAL THAT THERE IS A LARGE DIFFERENCE BETWEEN ENGINE RPM AND COMPRESSOR RPM.
* A SIGNAL THAT THE REFRIGERANT PRESSURE IS ABNORMALLY HIGH OR LOW.
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AUTOMATIC AIR CONDITIONER
222 22 22
2
1A
5
222 22 22
I32
E11
I27 I27
EB IJ
1K
2
IN16
II1
5
II1
2
IR24
IJ2
2
EB1 2
IR22
IR2
1
IR2
6
IN1
1
IN1
3
IE 2
12
EB1
1
M
1 2
4
2 1
A
B
BB
1212 IR2
10
IR2 9
23 34
R±L R±L
R±LR±L
R±L
R±Y L±RL±Y
L±W
Y
B±R
R
L±W R±L
B
R±L
R±L
R±L
R±L
B
L±R
W
W
L±W
L±W L±R
W±B
L±R
L
L±R
W±B
W±B W±B W±B W±BRY
B±R
W±B
R L L
R±L
R±L
FROM POWER SOURCE SYSTEM
(
SEE PAGE 56 )
10A
HEATER
60A
HEATER
HEA TER
RELAY A/C MAGNETIC
CLUTCH RELAYENGINE AND ECT ECU
DEFOGGER
RELAY
BLOWER
MOTOR
A/C MAGNETIC CLUTCH BLOWER RESISTOR
(FOR LOW SPEED )
A/C POWER
TRANSISTOR A1 7
,A1 8
B3
A2
E9
B2 ACMG A/C
B
R±Y43 13 51 42
2 12
34
R±LB
L±O
W±G
IN1
2
AA
1
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FRESH RECIRC
21
II1
7IE1 13
IQ1
13
IR2
5IR1 2IR11IG1 16 IR1 3 I27
B±Y
R±Y L±RL±Y
L±W
Y
B±R R±L
R±L
BR
B±YG±RLG
GR BR
R± Y
B±Y
R±Y
R±Y
GR
A
8A 7A9B 2A4C6A 3C 5C4A 10 B 23 B11
GR
R±Y
G
G±R B±Y
R±G
L±R L±Y
L±W
Y
B± R
VSV
(
FOR WATER VALVE )
AIR INLET CONTROL
SERVO MOTOR A33
V4
62 5 3 1
BR±W
A1 2 , A 1 3 ,A1 4
A/C CONTROL ASSEMBLY CABM
BLR LV HR A/C IN MGC IG+ WV MREC MFRS RDFGR TPI ST
LG
G±R
BR±W
2 1
NOISE FILTER
( FOR A/C SYSTEM )
N4
R±G R±L
IQ 1
16 IR1 6 Y±G
BR
Y± GBR BR
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AUTOMATIC AIR CONDITIONER
MHOT COOL
I27 I27
I27
I27
E18
I28
EB1
7
IN1
4 II1 4
IQ1
5
II1
1
IR2
3 IR1
4IR1 10 IR1 9IR18IR1 13 IR112
2 1
2 1
2 1
B
8B 3B10 B 9B18 B 22 C 2C3B 20 B 25 C 9C8 BR
BR±W
BR
BR ±W BR
BR
BR±W
G±W
V
R±Y
BR
BR
BR
BR
BR
P± B
G±Y
P±B
P
L±Y
BR±W
G±W
V
R±Y
Y± R
Y±B
W BR±W
Y± R
BR BR±W
G± W
V
R±Y
Y±G Y±L
TAM LCKI TW TE S5 TP MH MC SG TPM MDEF MFACE 26 1 54
AIR MIX CONTROL
SERVO MOTOR
A/C CONTROL ASSEMBLY
A/C LOCK SENSOR A/C AMBIENT
TEMP. SEN SOR A/C SOLAR SENSOR
A1
A2
A20
A27
A12 , A 1 3 , A 1 4 CAB
BR± W
I27
I27
3 1
W4
WATER TEMP. SENSOR2 1 IR1
5
IR2
8IR1 7
I29IR1
11A/C EVAPORATOR
TEMP. SENSOR A16
BR±W
Y±GY±L W
BR
BR
Y±G
BR BR±W
BR BR BR
BR ±W
BR
BR BR
G± Y
LG±R G± Y
Y±R Y± B WW
BRBR
IQ1
6
BR BR
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231
IQ1
1IQ1 9
IQ1
15 IK1
8
M
1B
53A 5
3A
6
3B
3 1E
11 3G 51E
2
2
2615 4 1
4 398765 4
B
4B 12 B 13 B14 B 15 B16 C 1C 15 B1
BR
BR±W Y±GY±L W
TACH
BR
BR±W
Y±GY±L
W R
R
R
L±R L±R
B
B
B L±RR
B±Y
B±R Y
G±O
V±R
V±W
L±R
SAUT SET1 SET2 SET3 SET4 SET5 +B ACC IGN
A/C VENT MODE CONTROL
SERVO MOTOR
ROOM TEMP. CONTROL SW
A/C CONTROL ASSEMBLY IGNITER
10A
DOME
15A
CIG
FROM POW ER SOURCE
SYSTEM(
SEE PAGE 56 )
A12 ,A13
,A14
A15
I2
A28
A/C CONTROL SW AND RADIO SWDEF FACE
CAB
AUTO
2
B
7 2 1
IQ1
17 BR
BR
BR
BR
Y±L
Y±L
TR
A1 9
A/C ROOM TEMP.
SENSOR
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AUTOMATIC AIR CONDITIONER
IR2
7IQ1 8
IQ1
19
IQ1
10
IQ1
4 1E
18
3H
13
1J
1
3E
33H 12
ED IF EA 4
1
L±B
L±B
W±B
P±L
P±B
W±G
W±B P±L
P±B
W±G
L±B
P±L
P±B
P±B
BR
W±B
W±B W±B W±B
L±G
A
2B 5C7B17 B 6 E1 E1
A/C TC TC OP1
DIN
DOUT
E
PSW
REOST
A/C CONTROL ASSEMBLY TDCL
(
TOTAL DIAGNOSTIC
COMMUNICATION LINK )CHECK
CONNECTOR
A/C PRESSURE SW
A1 2 , A1 3 ,
A14 T6 C3
A3
11 4 11
3
CAB IK1
10
P±B
3A
12
3H
10 3G 33A
1
A
5A 6
IQ1
18 IQ1 23A
9
3G
2 IG1
5 1I
3
W±B
G±O
G±O
G±O
G
G LL
W±G
8
6 FROM POWER SOURCE SYSTEM
(
SEE PAGE 56 )
7. 5A
PANEL
I16
INTEGRATION
RE LAY
(
CA NADA )(
USA )
RHEOSTAT R9
TC TAIL IN1
5
A
5
A
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A 2 A/C MAGNETIC CLUTCH
4±GROUND : APPROX. 3.7

A 3 A/C PRESSURE SW
4±1 : OPEN ABOVE APPROX. 15.5KG/CM2 ( 30 PSI, 206 KPA) OR 27 KG/CM2
(384 PSI, 2648 KPA)
A17, A18 POWER TRANSISTOR
(B) 1± (A) 2 : APPROX. 2.0±2.4K

A12, A13, A14 A/C CONTROL ASSEMBLY
+B ± GROUND: ALWAYS APPROX. 10±14 VOLTS
IG + ± GROUND: APPROX. 10±14 VOLTS WITH IGNITION SW AT ON POSITION
HR ± GROUND: APPROX. 10±14 VOLTS WITH IGNITION SW AT ON POSITION AND DO NOT TURN THE BLOWER MOTOR
BELOW 1 VOLTS WITH IGNITION SW AT ON POSITION AND TURN THE BLOWER MOTOR
LP ± GROUND: NO CONTINUITY WITH PRESSURE LESS THAN 2.1 KG/CM
2 (30 PSI, 206 KPA) OR ABOVE 27 KG/CM2
(384 PSI, 2648 KPA)
ACC ± GROUND: APPROX. 10±14 VOLTS WITH IGNITION SW AT ACC OR ON POSITION
WV ± GROUND: 10±14 VOLTS AT START THE ENGINE AND MAX. COLD POSITION OF A/C TEMP. CONTROL SW
BELOW 1 VOLTS AT START THE ENGINE AND MAX. WARM POSITION OF A/C TEMP. CONTROL SW
MGC ± GROUND: BELOW 1 VOLTS AT START THE ENGINE, PUSH THE A/C AUTO SW AND A/C SW ON POSITION
10±14 VOLTS AT START THE ENGINE, PUSH THE A/C AUTO SW AND A/C SW OFF POSITION
BLR ± GROUND: BELOW 1.5 VOLTS WITH THE IGNITION SW ON AND TURN THE BLOWER MOTOR
S5 ± GROUND: 4±6 VOLTS WITH THE IGNITION SW ON
SG ± GROUND: ALWAYS CONTINUITY
MH ± MC : 13±19 VOLTS WITH IGNITION SW OFF
MFRS ± GROUND: APPROX. 12 VOLTS WITH FRESH SW ON
MREC ± GROUND: APPROX. 12 VOLTS WITH RECIRC SW ON
MFACE ± GROUND: APPROX. 12 VOLTS WITH FACE SW ON
MDEF ± GROUND: APPROX. 12 VOLTS WITH DEF SW ON
E ± GROUND: ALWAYS CONTINUITY
B 3 BLOWER RESISTOR (FOR LOW SPEED)
1±2 : APPROX. 2.6±3.0

: PARTS LOCATION
CODESEE PAGECODESEE PAGECODESEE PAGE
A 126A18B28E 9A28
A 226A1928I 227
A 326A2028I1629
A12C28A2728N 429
A13A28A2828R 929
A14B28A3328T 629
A1528B 228V 427
A1628B 328W 429
A17A28C 326
: RELAY BLOCKS
CODESEE PAGERELAY BLOCKS (RELAY BLOCK LOCATION)
219ENGINE COMPARTMENT LEFT
: JUNCTION BLOCK AND WIRE HARNESS CONNECTOR
CODESEE PAGEJUNCTION BLOCK AND WIRE HARNESS (CONNECTOR LOCATION)
1A20ENGINE ROOM MAIN WIRE1B20ENGINE ROOM MAIN WIRE
1E20INSTRUMENT PANEL WIRE
1I
1J20COWL WIRE
1K
20COWL WIRE
3A
3B
3E23INSTRUMENT PANEL WIRE
3G
3H
SERVICE HINTS
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AUTOMATIC AIR CONDITIONER
: CONNECTOR JOINING WIRE HARNESS AND WIRE HARNESS
CODESEE PAGEJOINING WIRE HARNESS AND WIRE HARNESS (CONNECTOR LOCATION)
EB134ENGINE WIRE AND ENGINE ROOM MAIN WIRE (FRONT SIDE OF R/B NO. 2)
IE136ENGINE ROOM MAIN WIRE AND COWL WIRE (R/B NO. 4)
IE236ENGINE ROOM MAIN WIRE AND COWL WIRE (BEHIND GLOVE BOX)
IG136INSTRUMENT PANEL WIRE AND COWL WIRE (R/B NO. 5)
II136ENGINE WIRE AND A/C WIRE (BEHIND GLOVE BOX)
IJ236ENGINE WIRE AND COWL WIRE (RIGHT KICK PANEL)
IK136ENGINE WIRE AND INSTRUMENT PANEL WIRE (RIGHT KICK PANEL)
IN138ENGINE ROOM MAIN WIRE AND A/C WIRE (BEHIND GLOVE BOX)
IQ138INSTRUMENT PANEL WIRE AND CONSOLE BOX WIRE (UNDER THE INSTRUMENT PANEL CENTER)
IR138CONSOLE BOX WIRE AND A/C SUB WIRE (BEHIND GLOVE BOX)IR238CONSOLE BOX WIRE AND A/C SUB WIRE (BEHIND GLOVE BOX)
: GROUND POINTS
CODESEE PAGEGROUND POINTS LOCATION
EA34FRONT SIDE OF RIGHT FENDER
EB34FRONT SIDE OF LEFT FENDER
ED34REAR SIDE OF INTAKE MANIFOLD
IF36LEFT KICK PANEL
IJ36RIGHT KICK PANEL
: SPLICE POINTS
CODESEE PAGEWIRE HARNESS WITH SPLICE POINTSCODESEE PAGEWIRE HARNESS WITH SPLICE POINTS
E1134ENGINE ROOM MAIN WIREI2838CONSOLE BOX WIREE1834ENGINE WIREI2938CONSOLE BOX WIRE
I2738A/C WIREI3238ENGINE WIRE
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