Automatic A/c-Heater Systems: Other — Lexus RX I (1997-2003)

AUTOMATIC A/C-HEATER SYSTEM CONTROLS

Pushing AUTO button selects automatic operation of A/C-heater system. (Scheme 24) An indicator LED will illuminate, showing automatic temperature control has been selected. Pushing OFF button will turn A/C-heater system off. Rotating AUTO button (temperature control knob) will change passenger compartment temperature. Selected temperature is displayed on multi-display panel.

MODE button is used to manually select airflow. Panel, bi-level, floor, and floor/windshield manual selections may be made. Rotating MODE button (fan speed control knob) will change fan speed. Pushing OFF button will turn fan off. Selected fan speed is displayed on multi-display panel.

Air intake control (fresh/recirculated air) button is used to switch air intake between fresh air and recirculated air. An indicator LED will illuminate when recirculated air mode is selected. LED is off when fresh air mode is selected. If engine coolant temperature increases to more than a preset value, recirculated air mode will be automatically selected.

Manual selection of the A/C-heater system may be made by pressing the A/C button. If A/C compressor is inoperative, an operation indicator LED on will blink.

When FRONT defrost button is pushed, A/C-heater system operates in fresh air mode. If fresh/recirculated air button is pushed, system returns to recirculated air mode. If FRONT button is pushed again, system returns to last mode used.

When rear window and outside mirror defog button is pushed, rear window and outside rear view mirror heating elements are energized. Defog function will automatically time out after 15 minutes. An operation indicator LED will illuminate during operation.

Scheme 24

Scheme 24: AUTOMATIC A/C-HEATER SYSTEM CONTROLS

A/C SYSTEM DOES NOT OPERATE

Check A/C ECU ground circuit. See «A/C ECU GROUND CIRCUIT»(ref-98896-S01783194692001070900000) under SYSTEM TESTS.
Check IG power source circuit. See «IG POWER SOURCE CIRCUIT»(ref-98896-S40633391672001060500000) under SYSTEM TESTS.

NO BLOWER CONTROL

Check heater main relay. See «RELAYS»(ref-98896-S17410865562001060500000) under COMPONENT TESTS.
Check body ECU. See appropriate MULTIPLEX CONTROL SYSTEMS article in ACCESSORIES & EQUIPMENT.
Check blower motor circuit. See «BLOWER MOTOR CIRCUIT»(ref-98896-S18778464122001060500000) under SYSTEM TESTS.
Check blower motor control relay. See «RELAYS»(ref-98896-S17410865562001060500000) under COMPONENT TESTS.
Check A/C ECU ground circuit. See «A/C ECU GROUND CIRCUIT»(ref-98896-S01783194692001070900000) under SYSTEM TESTS.

INSUFFICIENT AIRFLOW

Check blower motor circuit. See «BLOWER MOTOR CIRCUIT»(ref-98896-S18778464122001060500000) under SYSTEM TESTS.
Check blower motor control relay. See «RELAYS»(ref-98896-S17410865562001060500000) under COMPONENT TESTS.

NO COOL AIR COMES OUT

Ensure A/C system has proper refrigerant charge. See «A/C SYSTEM PERFORMANCE»(ref-98896-S38232799122001060500000) under SYSTEM TESTS. Correct refrigerant quantity as necessary.
Ensure drive belt tension is correct. See «SPECIFICATIONS»(ref-98896-S18517932722001060500000) . Adjust and/or replace drive belt as necessary.
Inspect A/C system performance. See «A/C SYSTEM PERFORMANCE»(ref-98896-S38232799122001060500000) under SYSTEM TESTS.
Check compressor circuit. See «COMPRESSOR CIRCUIT»(ref-98896-S04588624612001060500000) under SYSTEM TESTS.
Check pressure switch circuit. See «DTC B1423/23: PRESSURE SWITCH CIRCUIT»(ref-98896-S02407758962001060500000) under DIAGNOSTIC TESTS.
Check compressor lock sensor circuit. See «DTC B1422/22: COMPRESSOR LOCK SENSOR CIRCUIT»(ref-98896-S20624148892001060500000) under DIAGNOSTIC TESTS.
Check air mix door position sensor circuit. See «DTC B1431/31: AIR MIX DOOR POSITION SENSOR CIRCUIT»(ref-98896-S11476320192001060500000) under DIAGNOSTIC TESTS.
Check air mix door control servomotor circuit. See «DTC B1441/41: AIR MIX DOOR CONTROL SERVOMOTOR CIRCUIT»(ref-98896-S38788134982001060500000) under DIAGNOSTIC TESTS.
Check in-vehicle (room) temperature sensor circuit. See «DTC B1411/11: IN-VEHICLE TEMPERATURE SENSOR CIRCUIT»(ref-98896-S39561595772001060500000) under DIAGNOSTIC TESTS.
Check ambient temperature sensor circuit. See «DTC B1412/12: AMBIENT TEMPERATURE SENSOR CIRCUIT»(ref-98896-S26755857042001060500000) under DIAGNOSTIC TESTS.
Check A/C ECU ground circuit. See «A/C ECU GROUND CIRCUIT»(ref-98896-S01783194692001070900000) under SYSTEM TESTS.

NO WARM AIR COMES OUT

Check air mix door position sensor circuit. See «DTC B1431/31: AIR MIX DOOR POSITION SENSOR CIRCUIT»(ref-98896-S11476320192001060500000) under DIAGNOSTIC TESTS.
Check air mix door control servomotor circuit. See «DTC B1441/41: AIR MIX DOOR CONTROL SERVOMOTOR CIRCUIT»(ref-98896-S38788134982001060500000) under DIAGNOSTIC TESTS.
Check in-vehicle (room) temperature sensor circuit. See «DTC B1411/11: IN-VEHICLE TEMPERATURE SENSOR CIRCUIT»(ref-98896-S39561595772001060500000) under DIAGNOSTIC TESTS.
Check ambient temperature sensor circuit. See «DTC B1412/12: AMBIENT TEMPERATURE SENSOR CIRCUIT»(ref-98896-S26755857042001060500000) under DIAGNOSTIC TESTS.
Check evaporator temperature sensor circuit. See «DTC B1413/13: EVAPORATOR TEMPERATURE SENSOR CIRCUIT»(ref-98896-S01850174062001060500000) under DIAGNOSTIC TESTS.
Check A/C ECU ground circuit. See «A/C ECU GROUND CIRCUIT»(ref-98896-S01783194692001070900000) under SYSTEM TESTS.

OUTPUT AIR TEMPERATURE IS WARMER OR COOLER THAN SET TEMPERATURE OR RESPONSE IS SLOW

Ensure A/C system has proper refrigerant charge. See «A/C SYSTEM PERFORMANCE»(ref-98896-S38232799122001060500000) under SYSTEM TESTS. Correct refrigerant quantity as necessary.
Ensure drive belt tension is correct. See «SPECIFICATIONS»(ref-98896-S18517932722001060500000) . Adjust and/or replace drive belt as necessary.
Inspect A/C system performance. See «A/C SYSTEM PERFORMANCE»(ref-98896-S38232799122001060500000) under SYSTEM TESTS.
Check cooling fan system. See «COOLING FAN SYSTEM»(ref-98896-S27871544942001071100000) under SYSTEM TESTS.
Check solar sensor circuit. See «DTC B1421/21: SOLAR SENSOR CIRCUIT»(ref-98896-S37060373502001060500000) under DIAGNOSTIC TESTS.
Check in-vehicle (room) temperature sensor circuit. See «DTC B1411/11: IN-VEHICLE TEMPERATURE SENSOR CIRCUIT»(ref-98896-S39561595772001060500000) under DIAGNOSTIC TESTS.
Check ambient temperature sensor circuit. See «DTC B1412/12: AMBIENT TEMPERATURE SENSOR CIRCUIT»(ref-98896-S26755857042001060500000) under DIAGNOSTIC TESTS.
Check evaporator temperature sensor circuit. See «DTC B1413/13: EVAPORATOR TEMPERATURE SENSOR CIRCUIT»(ref-98896-S01850174062001060500000) under DIAGNOSTIC TESTS.
Check air mix door position sensor circuit. See «DTC B1431/31: AIR MIX DOOR POSITION SENSOR CIRCUIT»(ref-98896-S11476320192001060500000) under DIAGNOSTIC TESTS.
Check air mix door control servomotor circuit. See «DTC B1441/41: AIR MIX DOOR CONTROL SERVOMOTOR CIRCUIT»(ref-98896-S38788134982001060500000) under DIAGNOSTIC TESTS.
Check air inlet door position sensor circuit. See «DTC B1432/32: AIR INLET DOOR POSITION SENSOR CIRCUIT»(ref-98896-S24750309872001060500000) under DIAGNOSTIC TESTS.
Check air inlet door control servomotor circuit. See «DTC B1442/42: AIR INLET DOOR CONTROL SERVOMOTOR CIRCUIT»(ref-98896-S27628938122001060500000) under DIAGNOSTIC TESTS.
Check condenser fins for blockage or damage. If fins are bent, straighten using a screwdriver or pliers. Check condenser and fittings for refrigerant leaks. Repair as necessary.
Check evaporator and fittings for refrigerant leaks. Check heater core and fittings for leaks.
Check expansion valve operation. See «EXPANSION VALVE»(ref-98896-S23938218862001060500000) under COMPONENT TESTS.
Check A/C ECU ground circuit. See «A/C ECU GROUND CIRCUIT»(ref-98896-S01783194692001070900000) under SYSTEM TESTS.

NO TEMPERATURE CONTROL (ONLY MAXIMUM COLD OR HOT)

Check in-vehicle (room) temperature sensor circuit. See «DTC B1411/11: IN-VEHICLE TEMPERATURE SENSOR CIRCUIT»(ref-98896-S39561595772001060500000) under DIAGNOSTIC TESTS.
Check ambient temperature sensor circuit. See «DTC B1412/12: AMBIENT TEMPERATURE SENSOR CIRCUIT»(ref-98896-S26755857042001060500000) under DIAGNOSTIC TESTS.
Check air mix door position sensor circuit. See «DTC B1431/31: AIR MIX DOOR POSITION SENSOR CIRCUIT»(ref-98896-S11476320192001060500000) under DIAGNOSTIC TESTS.
Check air mix door control servomotor circuit. See «DTC B1441/41: AIR MIX DOOR CONTROL SERVOMOTOR CIRCUIT»(ref-98896-S38788134982001060500000) under DIAGNOSTIC TESTS.
Check A/C ECU ground circuit. See «A/C ECU GROUND CIRCUIT»(ref-98896-S01783194692001070900000) under SYSTEM TESTS.

NO AIR INLET CONTROL

Check air inlet door position sensor circuit. See «DTC B1432/32: AIR INLET DOOR POSITION SENSOR CIRCUIT»(ref-98896-S24750309872001060500000) under DIAGNOSTIC TESTS.
Check air inlet door control servomotor circuit. See «DTC B1442/42: AIR INLET DOOR CONTROL SERVOMOTOR CIRCUIT»(ref-98896-S27628938122001060500000) under DIAGNOSTIC TESTS.
Check A/C ECU ground circuit. See «A/C ECU GROUND CIRCUIT»(ref-98896-S01783194692001070900000) under SYSTEM TESTS.

NO AIRFLOW MODE

Check air outlet door position sensor circuit. See «DTC B1433/33: AIR OUTLET DOOR POSITION SENSOR CIRCUIT»(ref-98896-S08191670742001060500000) under DIAGNOSTIC TESTS.
Check air outlet door control servomotor circuit. See «DTC B1443/43: AIR OUTLET DOOR CONTROL SERVOMOTOR CIRCUIT»(ref-98896-S19344203962001060500000) under DIAGNOSTIC TESTS.
Check A/C ECU ground circuit. See «A/C ECU GROUND CIRCUIT»(ref-98896-S01783194692001070900000) under SYSTEM TESTS.

ENGINE IDLE UP DOES NOT OCCUR, OR IS CONTINUOUS

Check compressor circuit. See COMPRESSOR CIRCUIT under SYSTEM TESTS. Check ECM.

BLINKING A/C INDICATOR

Check compressor circuit. See «COMPRESSOR CIRCUIT»(ref-98896-S04588624612001060500000) under SYSTEM TESTS.
Check compressor lock sensor circuit. See «DTC B1422/22: COMPRESSOR LOCK SENSOR CIRCUIT»(ref-98896-S20624148892001060500000) under DIAGNOSTIC TESTS.
Check A/C ECU ground circuit. See «A/C ECU GROUND CIRCUIT»(ref-98896-S01783194692001070900000) under SYSTEM TESTS.

DISPLAYED SET TEMPERATURE DOES NOT CHANGE WITH TEMPERATURE CONTROL SWITCH

Check A/C ECU ground circuit. See A/C ECU GROUND CIRCUIT under SYSTEM TESTS.

Indicator Check

Press and hold AUTO button and fresh/recirculated air control buttons, and turn ignition on. Indicators will flash on and off at one-second intervals, 4 times in succession, as an indicator check. Press OFF button to cancel indicator check.
After indicator check is complete, system will enter self-diagnostic mode. Stored DTCs will appear in sequence on temperature display of multi-display panel. (Scheme 24) See «AUTOMATIC A/C-HEATER SYSTEM DIAGNOSTIC TROUBLE CODES»(ref-98896-S27169093302001060500000) table.
For a slower display rate, press driver side temperature switch to display DTCs one at a time. Press OFF button to exit self-diagnostics.

DTC Number	Condition/Affected Circuit
B1400/00	Normal
B1411/11 (1) (2)	In-Vehicle Temperature Sensor Circuit
B1412/12 (2) (3)	Ambient Temperature Sensor Circuit
B1413/13 (2)	Evaporator Temperature Sensor Circuit
B1421/21 (2) (4)	Solar Sensor Circuit
B1422/22 (5)	Compressor Lock Sensor Circuit
B1423/23 (6)	Refrigerant Pressure Switch Circuit
B1431/31 (7)	Air Mix Door Position Sensor Circuit
B1432/32 (7)	Air Inlet Door Position Sensor Circuit
B1433/33 (7)	Air Outlet Door Position Sensor Circuit
B1441/41 (8)	Air Mix Door Control Servomotor Circuit
B1442/42 (8)	Air Inlet Door Control Servomotor Circuit
B1443/43 (8)	Air Outlet Door Control Servomotor Circuit
(1) If in-vehicle temperature is -4°F (-20°C) or less, DTC B1411/11 may set even though system is normal. (2) A/C ECU will store DTC if malfunction has been detected for 8.5 minutes or more. (3) If outside air temperature is -58°F (-50°C) or less, DTC B1412/12 may set even though system is normal. (4) If testing is done in a dark area, DTC may set even though system is normal. Shine a light at solar sensor and recheck DTCs. (5) Malfunction is current. Code is not stored in memory. (6) Detected refrigerant pressures are less than 28 psi (2.0 kg/cm 2 ) or more than 455 psi (32 kg/cm 2 ) (7) A/C ECU will store DTC if malfunction has been detected for one minute or more. (8) A/C ECU will store DTC if malfunction has been detected for 15 seconds.

(1)	If in-vehicle temperature is -4°F (-20°C) or less, DTC B1411/11 may set even though system is normal.

(2)	A/C ECU will store DTC if malfunction has been detected for 8.5 minutes or more.

(3)	If outside air temperature is -58°F (-50°C) or less, DTC B1412/12 may set even though system is normal.

(4)	If testing is done in a dark area, DTC may set even though system is normal. Shine a light at solar sensor and recheck DTCs.

(5)	Malfunction is current. Code is not stored in memory.

(6)	Detected refrigerant pressures are less than 28 psi (2.0 kg/cm 2 ) or more than 455 psi (32 kg/cm 2 )

(7)	A/C ECU will store DTC if malfunction has been detected for one minute or more.

(8)	A/C ECU will store DTC if malfunction has been detected for 15 seconds.

AUTOMATIC A/C-HEATER SYSTEM DIAGNOSTIC TROUBLE CODES

Actuator Check

Perform «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-98896-S19809073382001060500000) procedure. When system enters self-diagnostic mode, press fresh/recirculated air control button. Each mode door, motor, and relay will operate at one-second intervals. Operation codes are displayed in order, starting with "0".
Actuator codes are displayed in temperature display. Perform step-by-step actuator check. Press A/C button to display DTCs one at a time and to step through checks one at a time.
Check airflow and temperature by hand. Each display DTC is associated with a system operating condition. (Scheme 25) Press OFF button to cancel actuator check mode.

Scheme 25

SYSTEM TESTS

WARNING

To avoid injury from accidental air bag deployment, read and carefully follow all SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM procedures in AIR BAG SYSTEM SAFETY article in GENERAL SERVICING.

A/C SYSTEM PERFORMANCE

Fully open doors. Start and operate engine at 1500 RPM. Set blower control switch to highest speed. Turn A/C system on. Observe sight glass on liquid tube (in front of condenser) and ensure no bubbles are present. If necessary, charge A/C system.
Ensure ambient temperature at air inlet is 86-95°F (30-35°C). Connect manifold gauge set to A/C system service valves. Place air selection switch to recirculated air position.
Start and operate engine at 2000 RPM. Set blower control switch to highest speed. Turn A/C system on and set temperature control dial to cool position. Ensure system operating pressures are within specifications. See «SPECIFICATIONS»(ref-98896-S18517932722001060500000) .

A/C ECU GROUND CIRCUIT

Remove instrument cluster (A/C ECU), leaving harness connectors connected. See «INSTRUMENT CLUSTER (A/C ECU)»(ref-98896-S37121188372001070900000) under REMOVAL & INSTALLATION.
Measure resistance (backprobe) between A/C ECU terminal C14-22 (White/Black wire) and ground. see scheme 3or see scheme 4. See «WIRING DIAGRAMS»(ref-98896-S06345939912001060500000).
If resistance is more than one ohm, check wiring harness and connector terminals. Repair as necessary. If resistance is one ohm or less, temporarily substitute a known-good instrument cluster (A/C ECU) and retest system. Replace instrument cluster (A/C ECU) as necessary.

BACK-UP POWER SOURCE CIRCUIT

Remove instrument cluster (A/C ECU), leaving harness connectors connected. See «INSTRUMENT CLUSTER (A/C ECU)»(ref-98896-S37121188372001070900000) under REMOVAL & INSTALLATION.
Measure voltage (backprobe) between A/C ECU connector terminal C14-3 (White/Blue wire) and ground. see scheme 3or see scheme 4. See «WIRING DIAGRAMS»(ref-98896-S06345939912001060500000).
If battery voltage is present, no problem is indicated at this time. If battery voltage is not present, check ECU-B fuse (7.5-amp) located in engine compartment junction block.
If fuse is okay, check wiring harness and connectors between A/C ECU and battery. Repair as necessary. If fuse is blown, replace fuse and check for short in harness and components connected to HEATER fuse (15-amp) located in instrument panel junction block. Repair as necessary.

BLOWER MOTOR CIRCUIT

Remove A/C ECU (instrument cluster ECU), leaving harness connectors connected. Turn ignition on. Operate blower motor. Measure voltage between A/C ECU terminal C14-4 (Pink/Blue wire) and ground. If voltage is 1-3 volts, no problem is indicated at this time. If voltage is not 1-3 volts, go to next step.
Check blower motor. See «BLOWER MOTOR»(ref-98896-S17571181522001071000000) under COMPONENT TESTS. If blower motor operates smoothly, go to next step. Replace blower motor if it does not operate smoothly.
Check blower motor control relay. See «RELAYS»(ref-98896-S17410865562001060500000) under COMPONENT TESTS. Replace blower motor control relay if operation is not as specified. If blower motor control relay is okay, check wiring harness and connectors between blower motor, blower motor control relay and A/C ECU. Repair as necessary.

COMPRESSOR CIRCUIT

Start engine. Press AUTO button. Press A/C button on and off, and measure voltage between Engine Control Module (ECM) connector (E9 on 2000; E6 on 2001) terminal No. 6 (Light Green/Black wire) and ground. see scheme 5or see scheme 6. See «WIRING DIAGRAMS»(ref-98896-S06345939912001060500000).
With A/C switch on, voltage should be 10-14 volts. With A/C switch off, voltage should be zero volts. If voltage is as specified, temporarily substitute a known-good ECM and/or A/C ECU, then retest system. If voltage is not as specified, go to next step.
Using a fused jumper wire, apply battery voltage to A/C compressor clutch terminal No. 3 (Black/Yellow wire). Connect ground to compressor body. If clutch coil energizes, go to next step. If clutch coil does not energize, replace compressor clutch coil.
Check wiring harness and connectors between A/C compressor and A/C compressor (magnetic) clutch relay. See «WIRING DIAGRAMS»(ref-98896-S06345939912001060500000). Check wiring harness and connectors between A/C compressor (magnetic) clutch relay and ECM, and between ECM and A/C ECU. Repair wiring and connectors as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good ECM and/or A/C ECU, then retest system.

COOLING FAN SYSTEM

Remove radiator cap and insert a thermometer into opening. Start engine and monitor coolant temperature and cooling fan operation. See «COOLING FAN OPERATING CONDITIONS»(ref-98896-S00459698542001071300000) table.
If cooling fans do not operate as specified, check cooling fan motors. See «COOLING FAN MOTOR»(ref-98896-S24015487792001060500000) under COMPONENT TESTS. If cooling fan motors are okay, check Engine Coolant Temperature (ECT) sensors. See «ENGINE COOLANT TEMPERATURE SENSORS»(ref-98896-S35798348542001071300000) under COMPONENT TESTS. Replace sensor as necessary.
If ECT sensors are okay, check cooling fan relays. See «RELAYS»(ref-98896-S17410865562001060500000) under COMPONENT TESTS. Replace relays as necessary. If no problems are found, check wiring harnesses and connectors between components and A/C ECU. See «WIRING DIAGRAMS»(ref-98896-S06345939912001060500000) .

Condition	Fan Operation
Coolant Temperature 194°F (90°C) Or Less	Low Speed
Coolant Temperature 203°F (95°C) Or More	High Speed
Refrigerant Pressure Less Than 220 psi (15.5 kg/cm 2 )	Low Speed
Refrigerant Pressure 220 psi (15.5 kg/cm 2 ) Or More	High Speed

COOLING FAN OPERATING CONDITIONS

IG POWER SOURCE CIRCUIT

Remove instrument cluster (A/C ECU), leaving harness connectors connected. See «INSTRUMENT CLUSTER (A/C ECU)»(ref-98896-S37121188372001070900000) under REMOVAL & INSTALLATION. Turn ignition on.
Measure voltage (backprobe) between A/C ECU terminal C14-1 (Red/Blue wire on 2000; Red/White wire on 2001) and ground. If battery voltage is present, temporarily substitute a known-good instrument cluster (A/C ECU) and retest system. Replace instrument cluster (A/C ECU) if necessary.
If battery voltage is not present, check HEATER fuse (15-amp) located in instrument panel junction block. If fuse is okay, check wiring harness and connectors between A/C ECU and battery. Repair as necessary. If fuse is blown, replace fuse and check for short in harness and components connected to HEATER fuse. Repair as necessary.

AIR INLET DOOR CONTROL SERVOMOTOR

Remove blower motor unit. See «BLOWER UNIT»(ref-98896-S25390350972001060500000) under REMOVAL & INSTALLATION. Disconnect air inlet control servomotor connector.
Using a fused jumper wire, apply battery voltage to air inlet control servomotor connector terminal No. 6 (Red wire). Connect terminal No. 7 (Brown/White wire on 2000; Brown/Yellow wire on 2001) to ground. See «WIRING DIAGRAMS»(ref-98896-S06345939912001060500000). Servomotor lever should move smoothly to recirculated air (REC) position. (Scheme 26)
Transpose power and ground leads. Servomotor lever should move smoothly to fresh air (FRS) position. If servomotor does not function as specified, replace servomotor.

Scheme 26

AIR INLET DOOR CONTROL SERVOMOTOR POSITION SENSOR

Disconnect air mix control servomotor connector. Measure resistance between air inlet door control servomotor terminal No. 1 (Violet/White wire) and No. 3 (Black/White wire). (Scheme 26) See «WIRING DIAGRAMS»(ref-98896-S06345939912001060500000). Sensor resistance should be 4200-7800 ohms.
Operate servomotor. See «AIR INLET DOOR CONTROL SERVOMOTOR»(ref-98896-S26115652422001060500000). Measure resistance between air mix door control servomotor terminals No. 1 and 5. See «AIR INLET DOOR CONTROL SERVOMOTOR RESISTANCE»(ref-98896-S27075193062001071200000) table. Replace servomotor if resistance is not as specified.

Door Position	Resistance
Recirculation (REC)	3100-5800
Fresh (FRS)	800-1600

AIR INLET DOOR CONTROL SERVOMOTOR RESISTANCE

AIR MIX DOOR CONTROL SERVOMOTOR

Disconnect air mix door control servomotor connector. Using a fused jumper wire, apply battery voltage to air mix door control servomotor terminal No. 7 (Yellow/Green wire). Connect terminal No. 6 (Yellow wire) to ground. See «WIRING DIAGRAMS»(ref-98896-S06345939912001060500000). Servomotor lever should move smoothly to hot position. (Scheme 27)
Transpose power and ground leads. Servomotor lever should move smoothly to cool position. (Scheme 27) If servomotor does not function as specified, replace servomotor.

Scheme 27

AIR MIX DOOR CONTROL SERVOMOTOR POSITION SENSOR

Disconnect air mix door control servomotor connector. Measure resistance between air mix door control servomotor terminals No. 1 and 3. (Scheme 27) See «WIRING DIAGRAMS»(ref-98896-S06345939912001060500000). Sensor resistance should be 4200-7800 ohms.
Operate air mix door control servomotor. Measure resistance between air mix door control servomotor terminals No. 1 and 5. See «AIR MIX DOOR CONTROL SERVOMOTOR»(ref-98896-S41512766652001060500000). See «AIR MIX DOOR CONTROL SERVOMOTOR RESISTANCE»(ref-98896-S35329548312001071100000) table. Replace servomotor if resistance is not as specified.

Door Position	Resistance
Maximum Cool	3600-6800
Maximum Hot	500-1100

AIR MIX DOOR CONTROL SERVOMOTOR RESISTANCE

AIR OUTLET DOOR CONTROL SERVOMOTOR

Disconnect air outlet door (vent mode) control servomotor connector. Using a fused jumper wire, apply battery voltage to air outlet door control servomotor connector terminal No. 6 (Light Green/Black wire).
Connect terminal No. 7 (White wire) to ground. (Scheme 28) Servomotor lever should move smoothly to defrost position.
Transpose power and ground leads. Servomotor lever should move smoothly to face position. If servomotor does not function as specified, replace servomotor.

Scheme 28

AIR OUTLET DOOR CONTROL SERVOMOTOR POSITION SENSOR

Disconnect air outlet door control servomotor connector. Measure resistance between air outlet door control servomotor terminal No. 1 (Black/Yellow wire) and terminal No. 3 (Green/Black wire). (Scheme 28) Sensor resistance should be 4200-7800 ohms.
Operate air outlet door control servomotor. See «AIR OUTLET DOOR CONTROL SERVOMOTOR»(ref-98896-S27705914882001060500000). Measure resistance between air outlet door control servomotor terminal No. 1 (Black/Yellow wire) and terminal No. 5 (Light Green/Red wire). See «AIR OUTLET DOOR CONTROL POSITION SENSOR RESISTANCE»(ref-98896-S14687893112001071200000) table. Replace servomotor if resistance is not as specified.

Door Position	(1) Resistance
Defrost	500-1100
Vent (Face)	3600-6800
(1) As air outlet door moves from defrost position to face position, resistance should gradually decrease.

(1)	As air outlet door moves from defrost position to face position, resistance should gradually decrease.

AIR OUTLET DOOR CONTROL POSITION SENSOR RESISTANCE

AMBIENT TEMPERATURE SENSOR

Remove clip and ambient temperature sensor from front bumper reinforcement. Disconnect ambient temperature sensor connector. Measure sensor resistance while heating sensor. See AMBIENT TEMPERATURE SENSOR SPECIFICATIONS table. If resistance is not as specified, replace sensor.

Sensor Temperature - °F (°C)	(1) Ohms
77 (25)	1600-1800
122 (50)	500-700
(1) As temperature increases, resistance should gradually decrease.

(1)	As temperature increases, resistance should gradually decrease.

AMBIENT TEMPERATURE SENSOR SPECIFICATIONS

BLOWER MOTOR

Remove blower motor. See BLOWER MOTOR under REMOVAL & INSTALLATION. Using a fused jumper wire, apply battery voltage to blower motor terminal No. 2 (Red wire). Connect blower motor terminal No. 1 (Black wire) to battery ground. Replace blower motor if it does not operate smoothly.

COMPRESSOR LOCK SENSOR

Raise and support vehicle. Disconnect compressor lock sensor connector, located at compressor. Measure resistance between sensor terminals No. 1 (White/Blue wire) and No. 2 (Brown wire) at specified temperatures. See COMPRESSOR LOCK SENSOR SPECIFICATIONS table. Replace sensor if resistance is not as specified.

Sensor Temperature - °F (°C)	Ohms
68 (20)	990-1210
212 (100)	1280-1550

COMPRESSOR LOCK SENSOR SPECIFICATIONS

COOLING FAN MOTOR

Disconnect suspect cooling fan motor connector. Connect battery and ammeter in-series to fan motor connector terminal No. 2 (Blue/Black wire on condenser fan; Black wire on radiator fan). Connect terminal No. 1 (White wire on condenser fan; White/Black wire on radiator fan) to battery ground. Ensure fan motor operates smoothly and ammeter reading is 8.5-11.5 amps at 68°F (20°C).

No. 1 Engine Coolant Temperature Sensor

Drain coolant from radiator. Remove No. 1 Engine Coolant Temperature (ECT) sensor located at bottom of radiator. Immerse No. 1 ECT sensor tip and a thermometer in heated water. When temperature is more than 208°F (98°C), check continuity between sensor terminals. Continuity should not exist.
Allow water to cool. When temperature is less than 190°F (88°C), check continuity between sensor terminals. Continuity should exist. Replace sensor if continuity is not as specified. Refill cooling system, start engine and check for leaks.

No. 2 Engine Coolant Temperature Sensor

Drain coolant from radiator. Remove No. 2 Engine Coolant Temperature (ECT) sensor located at side of radiator. Immerse No. 2 ECT sensor tip and a thermometer in heated water. When temperature is more than 201°F (94°C), check continuity between sensor terminals. Continuity should not exist.
Allow water to cool. When temperature is less than 181°F (83°C), check continuity between sensor terminals. Continuity should exist. Replace sensor if continuity is not as specified. Refill cooling system, start engine and check for leaks.

EVAPORATOR TEMPERATURE SENSOR

Remove instrument panel. See «INSTRUMENT PANEL»(ref-98896-S14893859072001060500000) . Remove air duct from evaporator unit. Remove aspirator hose bolt. Disconnect sensor and carefully pry out evaporator sensor. Carefully detach sensor from bracket plate.
Measure evaporator temperature sensor resistance at specified temperature. See «EVAPORATOR TEMPERATURE SENSOR SPECIFICATIONS»(ref-98896-S41960622872001060500000) table.

Sensor Temperature - °F (°C)	(1) Ohms
32 (0)	4500-5200
59 (15)	2000-2700
(1) As temperature increases, resistance should gradually decrease.

(1)	As temperature increases, resistance should gradually decrease.

EVAPORATOR TEMPERATURE SENSOR SPECIFICATIONS

EXPANSION VALVE

Ensure A/C system is fully charged. Install manifold gauge set. Start and operate engine at 1500 RPM for at least 5 minutes. Ensure high pressure reading is 199-228 psi (14-16 kg/cm 2 ). If low pressure reading drops to 0 psi (0 kg/cm 2 ), replace expansion valve. See EXPANSION VALVE under REMOVAL & INSTALLATION.

A/C Compressor Clutch Control Circuit

Start and operate engine at 1500 RPM. Locate pressure switch in front of condenser (below high-pressure service valve) and disconnect connector. Connect A/C manifold gauge set. Set blower control switch to highest speed. Turn A/C system on and set temperature control to cool position.
Connect positive ohmmeter lead to pressure switch terminal No. 1 (Green/Red wire) and negative lead to No. 4 (White/Black wire). (Scheme 29) Observe refrigerant pressure and check for continuity between pressure switch terminals.
Continuity should exist as low-side pressure increases to more than 33 psi (2.3 kg/cm 2 ). Continuity should not exist as low-side pressure decreases to less than 28 psi (2.0 kg/cm 2 ).
Continuity should exist as high-side pressure decreases to less than 370 psi (26.0 kg/cm 2 ). Continuity should not exist as high-side pressure increases to more than 455 psi (32.0 kg/cm 2 ). If continuity is not as specified, replace pressure switch.

Scheme 29

Cooling Fan Control Circuit

Start and operate engine at 1500 RPM. Locate pressure switch in front of condenser (below high-pressure service valve) and disconnect connector. Connect A/C manifold gauge set. Set blower control switch to highest speed. Turn A/C system on and set temperature control to cool position.
Connect positive ohmmeter lead to pressure switch terminal No. 2 (White/Black wire) and negative lead to No. 3 (Red/White wire). (Scheme 29) Observe refrigerant pressure and check for continuity between pressure switch terminals.
On vehicles without towing package, continuity should exist as high-side pressure increases to more than 220 psi (15.5 kg/cm 2 ). Continuity should not exist as high-side pressure decreases to less than 178 psi (12.5 kg/cm 2 ). If continuity is not as specified, replace pressure switch.
On vehicles with towing package, continuity should exist as high-side pressure increases to more than 256 psi (18.0 kg/cm 2. Continuity should not exist as high-side pressure decreases to less than 199 psi (14.0 kg/cm 2 ). If continuity is not as specified, replace pressure switch.

A/C Compressor Magnetic Clutch Relay

Remove A/C compressor magnetic clutch (MG CLT) relay from left engine compartment junction block. Check continuity between relay terminals No. 1 and 2. (Scheme 30) Continuity should exist.
Using a fused jumper wire, connect battery voltage across relay terminals No. 1 and 2. Check for continuity between relay terminals No. 3 and 5. Continuity should exist. Replace relay if continuity is not as specified.

Scheme 30

Blower Motor Control Relay

Remove blower motor control relay, leaving harness connector attached. see scheme 18 Turn ignition on and operate blower motor at high speed. Backprobe blower motor control relay connectors and check for specified values. See TESTING BLOWER MOTOR CONTROL RELAY table. If test results are not as specified, replace blower motor control relay. If blower motor control relay is okay, repair wiring harness or connectors as necessary.

Check Between Terminals (1)	(2) Test Result
B3-1 (White/Black Wire) & Body Ground (3)	Continuity
B3-3 (Blue/Red Wire) & Body Ground (4)	Battery Voltage
B4-1 (Red Wire) & Body Ground (4)	Battery Voltage
B4-1 (Red Wire) & B4-2 (Black Wire) (5)	Battery Voltage
B3-2 (Pink/Blue Wire) & Body Ground (4)	1-3 Volts
(1) (Scheme 31) (2) Check relay with blower motor control relay connectors connected, ignition in ON position and blower motor operated at high speed. (3) Backprobe connector and check for continuity between specified relay terminal and body ground. (4) Backprobe connector and measure voltage between specified relay terminal and body ground. (5) Backprobe connector and measure voltage between specified relay terminals.

(1)	(Scheme 31)

(2)	Check relay with blower motor control relay connectors connected, ignition in ON position and blower motor operated at high speed.

(3)	Backprobe connector and check for continuity between specified relay terminal and body ground.

(4)	Backprobe connector and measure voltage between specified relay terminal and body ground.

(5)	Backprobe connector and measure voltage between specified relay terminals.

TESTING BLOWER MOTOR CONTROL RELAY

Scheme 31

No. 1 Cooling Fan Relay

Remove No. 1 cooling fan (FAN NO. 1) relay from left engine compartment junction block. Check continuity between relay terminals No. 3 and 4. (Scheme 32) Continuity should exist. Check continuity between relay terminals No. 1 and 2. Continuity should not exist.
Using a fused jumper wire, connect battery voltage across relay terminals No. 3 and 4. Check continuity between relay terminals No. 1 and 2. Continuity should exist. Replace relay if continuity is not as specified.

Scheme 32

No. 2 Cooling Fan Relay

Remove No. 2 cooling fan (FAN NO. 2) relay from left engine compartment junction block. Check continuity between relay terminals No. 2 and 4, and between terminals No. 3 and 5. (Scheme 33) Continuity should exist. Check for continuity between relay terminals No. 1 and 2. Continuity should not exist.
Using a fused jumper wire, connect battery voltage across relay terminals No. 3 and 5. Check for continuity between relay terminals No. 1 and 2. Continuity should exist. Replace relay if continuity is not as specified.

Scheme 33

No. 3 Cooling Fan Relay

Remove No. 3 cooling fan (FAN NO. 3) relay from left engine compartment junction block. Check continuity between relay terminals No. 3 and 5. (Scheme 34) Continuity should exist. Check continuity between relay terminals No. 1 and 2. Continuity should not exist.
Using a fused jumper wire, connect battery voltage across relay terminals No. 3 and 5. Check continuity between relay terminals No. 1 and 2. Continuity should exist. Replace relay if continuity is not as specified.

Scheme 34

Heater Main Relay

Remove driver side door scuff plate. Remove cowl side trim, lower finish panel and lower left insert. Remove 3 instrument panel junction block bolts. Remove heater main relay from relay block No. 1.
Check continuity between relay terminals No. 2 and 4, and between relay terminals No. 3 and 5. (Scheme 33) Continuity should exist. Check continuity between terminals No. 1 and 2. Continuity should not exist.
Using a fused jumper wire, connect battery voltage across relay terminals No. 3 and 5. Check continuity between terminals No. 1 and 2. Continuity should exist. Replace relay if continuity is not as specified.

IN-VEHICLE TEMPERATURE SENSOR

Disconnect room (in-vehicle) temperature sensor under left side of instrument panel. Measure sensor resistance while heating sensor. See IN-VEHICLE TEMPERATURE SENSOR SPECIFICATIONS table. If resistance is not as specified, replace in-vehicle temperature sensor.

Sensor Temperature - °F (°C)	(1) Ohms
77 (25)	1610-1780
122 (50)	550-650
(1) As temperature increases, resistance should gradually decrease.

(1)	As temperature increases, resistance should gradually decrease.

IN-VEHICLE TEMPERATURE SENSOR SPECIFICATIONS

SOLAR SENSOR

Remove solar sensor and disconnect sensor harness connector. Cover sensor with cloth. Connect positive lead of ohmmeter to sensor terminal No. 2 (Yellow/Black wire), and negative lead to terminal No. 1 (Blue wire). Measure and record resistance between sensor terminals.
Remove cloth. Subject sensor to bright light. Measure sensor resistance again. See «SOLAR SENSOR RESISTANCE SPECIFICATIONS»(ref-98896-S10094780482001060500000) table. If resistance is not as specified, replace sensor.

Condition	(1) Ohms
Sensor Covered By Cloth	Infinity (No Continuity)
Sensor Subjected To Bright Light	About 4000
(1) As light intensity decreases, resistance should increase.

(1)	As light intensity decreases, resistance should increase.

SOLAR SENSOR RESISTANCE SPECIFICATIONS

A/C UNIT

Note. Record rotational position of heater hose clamps for correct installation. Make match marks on drain hose for installation.

INSTRUMENT PANEL

Note. Four bolt sizes, two screw sizes, and two nut sizes are used to retain instrument panel components. Note size and shape of bolt, nut, and screw during removal.

Automatic A/c-Heater Systems: Other Lexus RX I