A/c-Heater System - Automatic: Other Lexus GS I

SYSTEM CONTROLS

The A/C control assembly consists of a liquid crystal display, a temperature control knob, fan speed control knob, airflow control knob, and various buttons which activate A/C-heater system, set desired temperature, direct discharged air to appropriate outlets, activate rear defogger, and control blower speed. (Scheme 23)

Scheme 23

HEATER CONTROL VALVE CABLE

Disconnect heater control valve cable, located in heater inlet line near engine bulkhead. Turn ignition on. Press A/C button. Set temperature control knob for maximum cooling. Set heater valve to cool position. (Scheme 24) Install control cable, and secure it with clamp.

Scheme 24

Indicator Check

1. While pressing and holding AUTO button and recirculated/fresh air button, turn ignition on. Indicators will flash on and off at one-second intervals, 4 times in succession, and a tone will sound as an indicator check. Press OFF button to cancel indicator check.
2. After indicator check is complete, system will enter self-diagnostic mode. Stored trouble codes will appear in sequence on temperature display panel. See «AUTOMATIC A/C-HEATER SYSTEM TROUBLE»(ref-36446-S22076091012001010900000) CODES table.
3. Press A/C switch button to display codes one at a time. If tone sounds when code is displayed, problem causing code currently exists. If tone does not sound when code is displayed, associated problem is past history, and does not currently exist. Press OFF button to exit self-diagnostics.

AUTOMATIC A/C-HEATER SYSTEM TROUBLE CODES

CLEARING CODES

Remove ECU-B fuse from No. 2 junction block for 10 seconds or longer to clear memory. Junction block is located at left side of engine compartment. After reinstalling fuse, verify only normal code (Code 00) appears.

ACTUATOR CHECK

1. Perform INDICATOR CHECK under «RETRIEVING CODES»(ref-36446-S17949974872001010900000). When system enters self-diagnostic mode, press recirculated/fresh air button. Each mode door, motor, and relay will operate at one-second intervals. Press A/C switch to display codes one at a time and to step through checks one at a time.
2. Check airflow and temperature by hand. Tone will sound each time display code changes. Each display code is associated with a system operating condition. (Scheme 25)or (Scheme 26). Press OFF button to cancel actuator check mode.

Scheme 25

Scheme 26

CODE 11: - IN-VEHICLE TEMPERATURE SENSOR CIRCUIT

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-36446-S21826621372001010900000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe A/C control assembly connector between terminalsA9-2 (Green wire) and A9-5 (Black/White wire). (Scheme 27) Measure voltage while heating the in-vehicle temperature sensor. Refer to the «IN-VEHICLE TEMPERATURE SENSOR CIRCUIT VOLTAGE SPECIFICATIONS»(ref-36446-S09602584022001010900000) table. IN-VEHICLE TEMPERATURE SENSOR CIRCUIT VOLTAGE SPECIFICATIONS Sensor Temperature °F (°C) (1) Volts 77 (25) 1.8-2.2 104 (40) 1.2-1.6 (1) As temperature increases, voltage should gradually decrease.
3. If voltage is as specified, temporarily substitute a known good A/C control assembly, then retest system. If voltage does not measure as specified, test the in-vehicle temperature sensor. Refer to the «IN-VEHICLE TEMPERATURE SENSOR TEST»(ref-36446-S01294286962001010900000) under TESTING. Replace sensor as necessary. If sensor is okay, go to next step.
4. Inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known good A/C control assembly. Retest system.

Scheme 27

CODE 12: - OUTSIDE TEMPERATURE SENSOR CIRCUIT

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-36446-S21826621372001010900000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe A/C control assembly connector between terminals A9-3 (Black wire) and A9-5 (Black/White wire). (Scheme 27) Measure voltage while heating the outside temperature sensor. Refer to the «OUTSIDE TEMPERATURE SENSOR CIRCUIT VOLTAGE SPECIFICATIONS»(ref-36446-S08156274952001010900000) table. OUTSIDE TEMPERATURE SENSOR CIRCUIT VOLTAGE SPECIFICATIONS Sensor Temperature °F (°C) (1) Volts 77 (25) 1.35-1.75 104 (40) 0.85-1.25 (1) As temperature increases, voltage should gradually decrease.
3. If voltage is as specified, temporarily substitute a known good A/C control assembly, then retest system. If voltage does not measure as specified, test outside temperature sensor. Refer to the «OUTSIDE TEMPERATURE SENSOR TEST»(ref-36446-S09020154892001010900000) under TESTING. Replace sensor as necessary. If sensor is okay, go to next step.
4. Inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known good A/C control assembly. Retest system.

CODE 13: - EVAPORATOR TEMPERATURE SENSOR CIRCUIT

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-36446-S21826621372001010900000) under REMOVAL & INSTALLATION.
2. Turn ignition on. Backprobe A/C control assembly connector between terminals A9-6 (Black/Blue wire) and A9-5 (Black/White wire). (Scheme 27)
3. Measure evaporator temperature sensor voltage at specified temperature. See «EVAPORATOR TEMPERATURE SENSOR CIRCUIT VOLTAGE»(ref-36446-S12220296852001010900000) SPECIFICATIONS table. EVAPORATOR TEMPERATURE SENSOR CIRCUIT VOLTAGE SPECIFICATIONS Sensor Temperature °F (°C) (1) Volts 32 (0) 2.0-2.4 59 (15) 1.4-1.8 (1) As temperature increases, voltage should gradually decrease.
4. If voltage is as specified, temporarily substitute a known good A/C control assembly, then retest system. If voltage does not measure as specified, test evaporator temperature sensor. Refer to the «EVAPORATOR TEMPERATURE SENSOR TEST»(ref-36446-S40927293262001010900000) under TESTING. Replace sensor as necessary. If sensor is okay, go to next step.
5. Inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known good A/C control assembly, then retest system.

CODE 14: - COOLANT TEMPERATURE SENSOR CIRCUIT

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-36446-S21826621372001010900000) under REMOVAL & INSTALLATION.
2. Turn ignition on. Backprobe A/C control assembly connector between terminals A9-7 (Green/Red wire) and A9-5 (Black/White wire). (Scheme 27)
3. Measure sensor circuit voltage at specified temperatures. See «COOLANT TEMPERATURE SENSOR CIRCUIT VOLTAGE SPECIFICATIONS»(ref-36446-S18485158372001010900000) table. COOLANT TEMPERATURE SENSOR CIRCUIT VOLTAGE SPECIFICATIONS Sensor Temperature °F (°C) (1) Volts 32 (0) 2.8-3.2 104 (40) 1.8-2.2 158 (70) 1.3-1.5 (1) As temperature increases, voltage should gradually decrease.
4. If voltage is as specified, temporarily substitute a known good A/C control assembly, then retest system. If voltage does not measure as specified, test the water temperature sensor. Refer to the «COOLANT (WATER) TEMPERATURE SENSOR TEST»(ref-36446-S14858259432001010900000) under TESTING. Replace sensor as necessary. If sensor is okay, go to next step.
5. Inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known good A/C control assembly, then retest system.

CODE 21: - SOLAR SENSOR CIRCUIT

Note. If testing is done in a dark area, Code 21 may set even though system is normal. Shine a bright light at solar sensor and recheck for Code 21.

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-36446-S21826621372001010900000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe the A/C control assembly connector between terminal A9-1 (Red/Yellow wire) and terminal A9-8 (Green/Black wire). (Scheme 27) Measure the solar sensor circuit voltage. Refer to the «SOLAR SENSOR CIRCUIT VOLTAGE SPECIFICATIONS»(ref-36446-S17116308932001010900000) table. SOLAR SENSOR CIRCUIT VOLTAGE SPECIFICATIONS Condition (1) Volts Sensor Subjected To Bright Light Less Than 0.8 Sensor Covered By Cloth 0.8-4.3 (1) As light intensity decreases, voltage should increase.
3. If voltage is as specified, temporarily substitute a known good A/C control assembly, then retest system. If voltage is not as specified, test solar sensor. See «SOLAR SENSOR TEST»(ref-36446-S13620331702001010900000) under TESTING. Replace sensor as necessary. If sensor is okay, go to next step.
4. Inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known good A/C control assembly, then retest system.

CODE 22: - COMPRESSOR LOCK SENSOR CIRCUIT

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-36446-S21826621372001010900000) under REMOVAL & INSTALLATION. Start engine. Press AUTO and A/C buttons to on position.
2. Backprobe A/C control assembly connector between terminalA8-20 (Yellow/Red wire) and ground. (Scheme 27) Measure sensor circuit voltage.
3. If battery voltage exists, no problem is indicated at this time. If voltage is not as specified, test compressor lock sensor. See «COMPRESSOR LOCK SENSOR TEST»(ref-36446-S35652119552001010900000) under TESTING. If sensor is okay, go to next step. Replace sensor as necessary.
4. Remove the A/C lock amplifier, leaving the harness connector attached. The A/C lock amplifier is located behind the glove box. Measure voltage or resistance between specified terminal and ground. Refer to the «A/C LOCK AMPLIFIER CIRCUIT SPECIFICATIONS»(ref-36446-S26878176662001010900000) table. (Scheme 28) If value is as specified, no problem is indicated at this time. If value is not as specified, go to next step.
5. Inspect wiring harness and connectors between A/C control assembly, A/C lock amplifier, and A/C compressor lock sensor. Repair harness and connectors as necessary. If wiring harness and connectors are okay, temporarily substitute known good A/C lock amplifier, and retest system.

A/C LOCK AMPLIFIER CIRCUIT SPECIFICATIONS

Scheme 28

CODE 23: - PRESSURE SWITCH CIRCUIT

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-36446-S21826621372001010900000) under REMOVAL & INSTALLATION. Install manifold gauge set. Turn ignition on.
2. Backprobe A/C control assembly connector between terminalA8-17 (Blue wire) and ground. (Scheme 27)
3. Start engine. Press A/C button to on position. Battery voltage should exist with refrigerant pressure less than 28 psi (2.0 kg/cm 2 ), or higher than 455 psi (32 kg/cm 2 ). If voltage is as specified, no problem is indicated at this time.
4. If voltage is not as specified, test pressure switch. See the «PRESSURE SWITCH TEST»(ref-36446-S16779998732001010900000) under TESTING. If switch is okay, go to next step. Replace pressure switch as necessary.
5. Inspect wiring harness and connectors between pressure switch and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known good A/C control assembly, then retest system.

CODE 31 OR 41: - AIR MIX DOOR POSITION SENSOR CIRCUIT

Note. For Code 41, see CODE 41 - AIR MIX SERVOMOTOR CIRCUIT for additional trouble shooting procedures.

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-36446-S21826621372001010900000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe A/C control assembly connector between terminals A9-9 (Blue/Orange wire) and A9-5 (Black/White wire). (Scheme 27)
3. Measure sensor circuit voltage while changing set temperature to activate air mix door. See «AIR MIX DOOR POSITION SENSOR»(ref-36446-S12644226682001010900000) SPECIFICATIONS table. AIR MIX DOOR POSITION SENSOR SPECIFICATIONS Set Temperature (1) Volts Maximum Cool 3.5-4.5 Maximum Hot 0.5-1.5 (1) As set temperature increases, voltage should gradually decrease.
4. If voltage is as specified, temporarily substitute a known good A/C control assembly, then retest system. If voltage does not measure as specified, test air mix door position sensor. Refer to the «AIR MIX DOOR POSITION SENSOR TEST»(ref-36446-S27214159182001010900000) under TESTING. If position sensor is defective, replace air mix door servomotor. If position sensor is okay, go to next step.
5. Inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known good A/C control assembly, then retest system.

CODE 32 OR 42: - AIR INLET DOOR POSITION SENSOR CIRCUIT

Note. For Code 42, see CODE 42 - AIR INLET SERVOMOTOR CIRCUIT for additional trouble shooting procedures.

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-36446-S21826621372001010900000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe A/C control assembly connector between terminals A9-10 (Red/Black wire) and A9-5 (Black/White wire). (Scheme 27)
3. Measure sensor voltage while pressing recirculation/fresh air button to change air inlet between recirculated and fresh air. As servomotor operates, note voltage. See «AIR INLET DOOR POSITION SENSOR»(ref-36446-S08570968622001010900000) SPECIFICATIONS table. AIR INLET DOOR POSITION SENSOR SPECIFICATIONS Position (1) Volts Recirculated Air 3.5-4.5 Fresh Air 0.5-1.5 (1) As door moves from recirculated air position toward fresh air position, voltage should gradually decrease.
4. If voltage is as specified, temporarily substitute a known good A/C control assembly, then retest system. If voltage does not measure as specified, test air inlet door position sensor. Refer to the «AIR INLET DOOR POSITION SENSOR TEST»(ref-36446-S36657109722001010900000) under TESTING. If air inlet door position sensor is defective, replace air inlet door servomotor. If position sensor is okay, go to next step.
5. Inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known good A/C control assembly, then retest system.

CODE 33 OR 43: - AIR OUTLET DOOR POSITION SENSOR CIRCUIT

Note. For Code 43, see CODE 43 - AIR OUTLET SERVOMOTOR CIRCUIT for additional trouble shooting procedures.

1. Remove A/C control assembly, leaving harness connectors attached. See «A/C CONTROL ASSEMBLY»(ref-36446-S21826621372001010900000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Backprobe A/C control assembly connector between terminals A9-11 (Yellow/Black wire) and A9-5 (Black/White wire). (Scheme 27)
3. Measure sensor circuit voltage while rotating airflow control knob from vent to defrost position. As servomotor operates, note voltage. See «AIR OUTLET DOOR POSITION SENSOR SPECIFICATIONS»(ref-36446-S04750014912001010900000) table. AIR OUTLET DOOR POSITION SENSOR SPECIFICATIONS Position (1) Volts Vent 3.5-4.5 Defrost 0.5-1.5 (1) As door moves from defrost position toward vent position, voltage should gradually increase.
4. If voltage is as specified, temporarily substitute a known good A/C control assembly, then retest system. If voltage does not measure as specified, test air outlet door position sensor. Refer to the «AIR OUTLET DOOR POSITION SENSOR TEST»(ref-36446-S42366983562001010900000) under TESTING. If position sensor is okay, go to next step. If air outlet door position sensor is defective, replace air outlet servomotor.
5. Inspect wiring harness and connectors between sensor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known good A/C control assembly, then retest system.

CODE 41: - AIR MIX SERVOMOTOR CIRCUIT

Note. See CODE 31 OR 41 - AIR MIX DOOR POSITION SENSOR CIRCUIT for additional trouble shooting procedures.

1. Warm engine to normal operating temperature. Perform «RETRIEVING CODES»(ref-36446-S17949974872001010900000) . After system enters self-diagnostic, perform «ACTUATOR CHECK»(ref-36446-S15494907242001010900000) . Press A/C switch button to enter step mode and display codes. See appropriate AIR MIX DOOR AIRFLOW table. Air mix door operation should be as specified. AIR MIX DOOR AIRFLOW (1995) Code Air Mix Door Expected Result 20-23 Fully Closed Cool Air Comes Out 24-25 Half Open Blend (Cool/Hot) Air Comes Out 26-29 Fully Open Hot Air Comes Out AIR MIX DOOR AIRFLOW (1996) Code Air Mix Door Expected Result 0-3 Fully Closed Cool Air Comes Out 4-5 Half Open Blend (Cool/Hot) Air Comes Out 6-9 Fully Open Hot Air Comes Out
2. If air mix door functions as specified, no problem is indicated at this time. If air mix door does not function correctly, test air mix door servomotor. See «AIR MIX DOOR SERVOMOTOR TEST»(ref-36446-S42453780482001010900000) under TESTING. If position sensor is okay, go to next step. Replace air mix door servomotor as necessary.
3. Inspect wiring harness and connectors between servomotor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known good A/C control assembly, then retest system.

CODE 42: - AIR INLET SERVOMOTOR CIRCUIT

Note. See CODE 32 OR 42 - AIR INLET DOOR POSITION SENSOR CIRCUIT for additional trouble shooting procedures.

1. Warm engine to normal operating temperature. Perform «RETRIEVING CODES»(ref-36446-S17949974872001010900000) . After system enters self-diagnostic code check mode, perform «ACTUATOR CHECK»(ref-36446-S15494907242001010900000) . Press A/C button to enter step mode and display codes. See appropriate AIR INLET DOOR AIRFLOW table. Air inlet door operation should be as specified. AIR INLET DOOR AIRFLOW (1995) Code Door Position 20-21 Fresh Air 22 Fresh/Recirculated Air 23-25 Recirculated Air 26-29 Fresh Air AIR INLET DOOR AIRFLOW (1996) Code Door Position 0-1 Fresh Air 2 Fresh/Recirculated Air 3-5 Recirculated Air 6-9 Fresh Air
2. If air inlet door functions as specified, no problem is indicated at this time. If air inlet door does not function correctly, test air inlet servomotor. See «AIR INLET DOOR SERVOMOTOR TEST»(ref-36446-S18961128042001010900000) under TESTING. Replace air inlet door servomotor as necessary. If air inlet door servomotor is okay, go to next step.
3. Inspect wiring harness and connectors between servomotor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known good A/C control assembly, then retest system.

CODE 43: - AIR OUTLET SERVOMOTOR CIRCUIT

Note. See CODE 33 OR 43 - AIR OUTLET DOOR POSITION SENSOR CIRCUIT for additional trouble shooting procedures.

1. Warm engine to normal operating temperature. Perform «RETRIEVING CODES»(ref-36446-S17949974872001010900000) . After system enters self-diagnostic mode, perform «ACTUATOR CHECK»(ref-36446-S15494907242001010900000) . Press A/C button to enter step mode and display codes. See appropriate AIR OUTLET DOOR AIRFLOW table. Air outlet door operation should be as specified. AIR OUTLET DOOR AIRFLOW (1995) Code Airflow Mode 20-21 Vent 22-24 Bi-Level 25-27 Foot 28 Foot/Defrost 29 Defrost AIR OUTLET DOOR AIRFLOW (1996) Code Airflow Mode 0-1 Vent 2-4 Bi-Level 5-7 Foot 8 Foot/Defrost 9 Defrost
2. If air outlet door servomotor functions as specified, no problem is indicated at this time. If air outlet door does not function as specified, test the air outlet servomotor. Refer to the «AIR OUTLET DOOR SERVOMOTOR TEST»(ref-36446-S39736058152001010900000) under TESTING. Replace servomotor as necessary. If air outlet servomotor is okay, go to next step.
3. Inspect wiring harness and connectors between servomotor and A/C control assembly. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known good A/C control assembly, then retest system.