1991 LEXUS SC400 evap

ABBREVIATIONS USED IN THIS
MANUAL
ABS Anti±Lock Brake System J/B Junction Block
A/C Air Conditioner LED Light Emitting Diode
ALR Automatic Locking Retractor LH Left±Hand
APPROX. Approximation LHD Left±Hand Drive
A/T, ATM Automatic Transmission LLC Long Life Coolant (Year Around Coolant)
ATF Automatic Transmission Fluid Max. Maximum
BTDC Before Top Dead Center Min. Minimum
BVSV Bimetal Vacuum Switching Valve MP Multipurpose
CALIF. Vehicles Sold in California N Neutral
CB Circuit Breaker OD, O/D Overdrive
DOHC Double Over Head Cam O/S Oversize
DP Dash Pot P & BV Proportioning and Bypass Valve
ECT Electronic Controlled Transmission PCV Positive Crankcase Ventilation
ECU Electronic Controlled Unit PS Power Steering
EFI Electronic Fuel Injection RH Right±Hand
EGR Exhaust Gas Recirculation RL Rear Left
ELR Emergency Locking Retractor RR Rear Right
EPR Evaporator Pressure Regulator RR, Rr Rear
ESA Electronic Spark Advance SRS Supplemental Restraint System
EVAP Evaporative (Emission Control) SSM Special Service Materials
EX Exhaust (manifold, valve) SST Special Service Tools
Ex. Except STD Standard
FIPG Formed in Place Gasket SW Switch
FL Front Left TDC Top Dead Center
FL Fusible Link TDCL Total Diagnostic Communication Link
FPU Fuel Pressure Up Temp. Temperature
FR Front Right TRAC Traction Control System
FR, Fr Front TWC Three±Way Catalyst
HAC High Altitude Compensation VSV Vacuum Switching Valve
IG Ignition VTV Vacuum Transmitting Valve
IN Intake (manifold, valve) w/ With
INT Intermittent w/o Without
ISC Idle Speed Control
IN±34±
INTRODUCTION Abbreviations Used in This Manual
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SERVICE SPECIFICATIONS
SERVICE DATA
Idle speedMagnetic clutch no engagedApprox. 700 rpm
Magnetic clutch engaged Approx. 700 rpm
Magnetic clutch clearance0.5 + 0.15 mm0.020 + 0.006 in.
TORQUE SPECIFICATIONS
Part tightenedN Vmkgf Vcmft Vlbf
Suction hose X Compressor2525018
Discharge hose X Compressor25250 18
Compressor X EngineBolt 49500 36
Nut 29300 22
Liquid tube X Receiver10100 7
Liquid tube X Condenser10100 7
Discharge tube X Condenser10100 7
Expansion valve X Evaporator5.455 48 in. Vlbf
Suction tube X A/C Unit10100 7
Liquid tube X A/C Unit10100 7
Equalizer tube X EPR25250 18
Pressure switch X Liquid tube101007
±
AIR CONDITIONING SYSTEM Service SpecificationsAC±141
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CONTROL FUNCTIONS
Interior Room Temperature Control System
(a) The desired temperature is set using the TEMP switch.
(b) From the input signals (room temperature sensor, ambient temperature sensor, evaporator temperaturesensor and solar sensor) and the temperature setting, the air conditioner con\
trol ECU determines the air
flow volume and outputs signals to the air mix servomotor.
(c) When it receives signals from the ECU, the air mix servomotor opens or close\
s the air mix damper to change the air flow temperature. When the temperature reaches the specified te\
mperature, it is detected
by the air mix damper position sensor and the ECU stops the servomotor.
HINT: If the desired temperature setting is 65 °F, the ECU forcedly sets the air mix damper to the Max Cool posi-
tion. If it is set at 85 °F, the ECU forcedly sets the air mix damper to the Max Hot position.
±
AIR CONDITIONING SYSTEM DescriptionAC±9
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EQUIPMENT
 Part Name\
 \
Note
 

Voltmeter\
 
\

\
Measures voltage 

Ammeter
\
 
\

\
Measures current
 Ohmmeter\
 \
Measures resistance
LUBRICANT
ItemCapacityClassificationItemccfl. ozClassification
Compressor oil
When replacing receiver
When replacing condenser
When replacing evaporator
20
40±50
40±500.7
1.4±1.7
1.4±1.7
ND OIL 6,
SUNISO No. 5GS or equivalent
AC±14±
AIR CONDITIONING SYSTEM Preparation Cooling System
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DIAGNOSTIC CODE CHART
If a malfunction code is displayed during the diagnostic code check (sens\
or check), check the circuit listed for
that code in the table below (Proceed to the page given for that circuit.)\
Code No.Diag. Code Detecting Condition
00 Normal
11 *1 Open or short in room temperature sensor circuit.
12 Open or short in ambient temperature sensor circuit.
13 Open or short in evaporator temperature sensor circuit.
14*2 Open or short in water temperature sensor circuit.
21*3 Open in solar sensor circuit.
21*3
 Short in solar sensor circuit.
22*4
 All conditions below are detected for 3 secs. or more.
 (a) Engine rpm : 450 rpm or more.
 (b) Ratio between engine and compressor rpm deviates 20% or more in c\
omparison to normal
operation.
23
 Open in pressure sensor circuit.
 Abnormal refrigerant pressure below 206 kPa (2.1 kgf/cm, 30 psi)
over 2,650 kPa (27 kgf/cm, 385 ps\
i)
31 Short to ground or power source circuit in Air Mix Damper position sens\
or circuit.
32 Short to ground or power source circuit in Air Inlet Damper position se\
nsor circuit.
33 Short to ground or power source circuit in Air Outlet Damper position s\
ensor circuit.
41 Air mix damper position sensor value does not change even if ECU operat\
es air mix servomotor.
42 Air inlet damper position sensor value does not change even if ECU oper\
ates air inlet servomotor.
43 Air outlet damper position sensor value does not change even if ECU ope\
rates air outlet
servomotor.
HINT: *1 If the room temp. is approx. ±20 °C (±4 °F) or lower, code 11 may be output even though the system
is normal.
*2 If the ambient temperature is approx. ±50 °C (±58 °F) or lower, a malfunction code may be output
even though the system is normal.
*3 If the check is being performed in a dark place, diagnostic code 21 (so\
lar sensor circuit abnormal) could be displayed.
In this case, perform diagnostic code check again while shining a light,\
such as an inspection light,
on the solar sensor.
If code 21 is still displayed, there could be trouble in the solar senso\
r circuit
AC±28
±
AIR CONDITIONING SYSTEM Troubleshooting
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Trouble AreaMemory*5See page
±±±
 Room temp. Sensor
 Harness or connector between room temp. sensor and A/C control assembly\
 A/C control assemblyO
(8.5 min. or more)AC±44
 Ambient temp. sensor
 Harness or connector between ambient temp. sensor and A/C control assem\
bly
 A/C control assemblyO
(8.5 min. or more)AC±46
 Evaporator temp. sensor
 Harness or connector between evaporator temp. sensor and A/C control
assembly A/C control assemblyO
(8.5 min. or more)AC±48
 Water temp. sensor
 Harness or connector between water temp. sensor and A/C control assembl\
y
 A/C control assemblyO
(8.5 min. or more)AC±50
 Solar sensor
H b d A/C l bl
±
AC 52 Solar sensor
 Harness or connector between sensor and A/C control assembly
 A/C control assemblyOAC±52
 A/C control assemblyO
(8.5 min. or more)
 Compressor drive belt Compressor lock sensor Compressor
 Harness and connector between A/C control assembly and compressor,
 compressor lock sensor
 A/C control assembly
±AC±54
 Pressure switch
 Harness or connector between pressure switch and A/C control assembly
 Refrigerant pipe line
 A/C control assembly
±AC±56
 Air mix damper position sensor A/C control assembly
 Harness or connector between air mix damper position sensor and
A/C control assemblyO
(1 min. or more)AC±58
 Air inlet damper position sensor A/C control assembly
 Harness or connector between air inlet damper position sensor and
A/C control assemblyO
(1 min. or more)AC±62
 Air outlet damper position sensor A/C control assembly
 Harness or connector between air outlet damper position sensor and
A/C control assemblyO
(1 min. or more)AC±66
 Air mix servomotor Air mix damper position sensor
 Harness and connector between A/C control assembly and air mix position\
sensor
 Harness and connector between A/C control assembly and air mix servomot\
or.O
(15 secs. or more)AC±58
AC±60
 Air inlet servomotor Air inlet damper position sensor
 Harness and connector between A/C control assembly and air inlet positi\
on sensor.
 Harness and connector between A/C control assembly and air inlet servom\
otor.O
(15 secs. or more)AC±62
AC±64
 Air outlet servomotor Air outlet damper position sensor
 Harness and connector between A/C control assembly and air outlet posit\
ion
sensor.
 Harness and connector between A/C control assembly and air outlet servo\
motor.
 A/C control assembly
O
(15 secs. or more)AC±66
AC±68
±
AIR CONDITIONING SYSTEM TroubleshootingAC±29
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Diag. Code 13Evaporator Temperature Sensor Circuit
CIRCUIT DESCRIPTION
This sensor detects the temperature inside the cooling unit and sends the ap\
propriate signals to the air
conditioner control assembly.
Code No.Diag. Code Detecting ConditionTrouble area
13
Open or short in evaporator temperature sensor
circuit.
Evaporator temperature sensor.

Harness or connector between evaporator
temperature sensor and A/C control
assembly.

A/C control assembly.
DIAGNOSTIC CHART
Check voltage between terminals TE
and SG of air conditioner control as-
sembly
Check evaporator temperature sensor.
Check harness and connector between air
conditioner control assembly and evapora-
tor temperature sensor (See page IN-27).
Check and replace air conditioner control
assembly. 10Proceed to next circuit inspection
shown on matrix chart (See page
AC-36
). However, when Diag. code
13 is displayed, check and replace
air conditioner control assembly.
Replace evaporator temperature
sensor.
Repair or replace harness or
connector.
AC±48±
AIR CONDITIONING SYSTEM Troubleshooting
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(1) Remove console upper panel. (See page BO±111 )
(2) Remove A/C Control Assembly with connectors still connected.
(3) Turn ignition switch ON.
Measure voltage between terminals TE and SG of air
conditioner control assembly connector at each tem-
perature.
Voltage
at 0°C (32°F) : 2.0~2.4 V
at 15°C (59°F) : 1.4~1.8 V
In addition, as the temperature increases, the
voltage decreases gradually.
Proceed to next circuit inspection shown on
matrix chart (See page AC-36).However,
when Diag. code 11 is displayed, check and
replace air conditioner control assembly.
Check voltage between terminals TE and SG of air conditioner control
assembly connector.
Check evaporator temperature sensor.
Remove evaporator temperature sensor(See page
AC-124 ).
Check resistance between terminals 1 and 2 of evap-
orator temperature sensor connector at each temper-
ature.
In addition, as the temperature increases, the
voltage decreases gradually.
Replace evaporator temperature sensor.
Check for open and short in harness and connector between air conditioner
control assembly and evaporator temperature sensor (See page IN-27).
Repair or replace harness or connector.
Check and replace air conditioner control
assembly.
Resistance
at 15°C (59°F) : 2.1~2.6k

at 0°C (32°F) : 4.6~5.1k

INSPECTION PROCEDURE
±
AIR CONDITIONING SYSTEM TroubleshootingAC±49
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