Automatic A/c-Heater Systems: Other Lexus LS III

SYSTEM CONTROLS

The A/C ECU consists of a liquid crystal display and various switches to activate A/C system, set desired temperatures, direct discharged air to appropriate vents, activate defoggers, and control blower fan speed. Separate temperature control switches provide independent driver and front passenger temperature control. On models equipped with multi display screen, A/C system will include push-button control switches and an A/C system status display screen. On models equipped with rear A/C and/or an air purifier, rear A/C is controlled from front and rear controls. Rear passenger A/C controls are located in rear center armrest with rear audio controls. (Scheme 8)or (Scheme 9).

Scheme 8

Scheme 9

CENTER VENT SWING REGISTER

Angle and orientation of front center vent swing register is controlled by A/C ECU. (Scheme 10) Control is based on selected temperature and signals from in-vehicle temperature sensor, solar sensors and occupant detection sensor (from air bag system). During initial stages of cooling down or warming up, center vent register airflow is directed toward occupants to enhance feeling of cooling or heating. As temperature stabilizes, register airflow is gradually directed away from front occupants.

Scheme 10

CLEAN A/C AIR FILTER CLOGGING JUDGEMENT

A/C ECU monitors A/C intake air mode and airflow volume. As A/C air filter becomes clogged, airflow volume decreases causing insufficient cooling and heating. When A/C ECU determines that air filter is clogged it displays CHANGE A/C FILTER on multi-information display located in instrument cluster.

COMPRESSOR SOLENOID CONTROL VALVE

A continuously variable capacity swashplate type compressor is used. Compressor capacity varies in accordance with A/C system cooling load. A solenoid control valve, located at rear of compressor, controls compressor suction pressure. (Scheme 11) By changing amperage applied to solenoid control valve, A/C ECU controls compressor discharge capacity by varying suction pressure. Compressor solenoid control valve is serviced by replacing compressor as an assembly.

EXHAUST GAS SENSOR

Automatic recirculation control is based on signals from an exhaust gas (smog) sensor. (Scheme 11) Exhaust gas sensor measures amounts of CO, HC and NOx gases present in intake air. Exhaust gas sensor is used to control fresh and recirculated air modes. During automatic A/C-heater operation if excessive amounts of exhaust gases are detected in front of vehicle, intake air is switched from fresh air mode to recirculated air mode. Manually turning off A/C will cancel exhaust gas automatic mode. Selecting AUTO mode during fan operation will turn A/C on and activate exhaust gas automatic mode.

Scheme 11

REAR A/C SYSTEM & AIR PURIFICATION

Rear A/C can be controlled from front or rear controls. Front A/C must be turned on for rear A/C to operate. Rear passenger A/C controls are located in rear center armrest with rear audio controls. Rear A/C system includes an optional cool box and air purifier. Air purification operates when rear blower motor is turned on using air purifier AUTO or LO HI button. A rear smoke sensor is included with rear air purifier to improve air quality. A rear solar sensor is located on rear deck to detect sunlight entering rear window and is used for rear A/C temperature control. (Scheme 9)and (Scheme 12).

Scheme 12

WATER VALVE CONTROL CABLE

Disconnect water valve control cable. Turn ignition on. Set temperature control switches to maximum cool position. Set water valve to maximum cool position. Install control cable. Secure cable clamp while lightly pushing outer cable in direction indicated by arrow. (Scheme 13)

Scheme 13

INITIALIZATION

Initialization should be performed after all repairs are completed. Initialization involves setting the air mix film and mode control film to their initial position. This position is then memorized by the A/C ECU as the standard position.

Automatic Initialization

Automatic initializing occurs when battery is reconnected and ignition switch is turned to ON position for the first time. When this occurs, front defrost indicator will blink. (Scheme 8) If mode indication is different from actual air outlet in actuator check, press rear defrost and OFF switches simultaneously, and turn ignition switch to ON or START position. Servomotor initializing will occur and defrost indicator will blink.

Manual Initialization

To manually initialize the system, depress rear defogger and OFF switches. With switches depressed, turn ignition switch from OFF to ON position. Front defogger indicator will illuminate during automatic or manual initialization.

EXHAUST GAS SENSOR SENSITIVITY

Note. Vehicle must be stopped when adjusting exhaust gas sensor sensitivity.

Press and hold fresh/recirculated air switch until a beep is heard. (Scheme 8) Press driver side temperature control switch up or down until sensor sensitivity is at desired level. Sensor sensitivity level is displayed on driver side temperature display and can be changed from +3 to -3. Previous display will return after a few seconds if a control switch is not operated.

A/C System Does Not Operate

1. Check IG power source circuit. See «IG POWER SOURCE CIRCUIT»(ref-99101-S41436495502001061800000) under SYSTEM TESTS.
2. Check ACC power source circuit. See «ACC POWER SOURCE CIRCUIT»(ref-99101-S32976624232001061800000) under SYSTEM TESTS.

No Blower Motor Control

1. Check front blower motor circuit. See «BLOWER MOTOR CIRCUIT»(ref-99101-S10101323542001061800000) under SYSTEM TESTS.
2. Check in-vehicle temperature sensor circuit. See «DTC B1411/11: IN-VEHICLE TEMPERATURE SENSOR CIRCUIT»(ref-99101-S16966428252001061800000) under SELF-DIAGNOSTICS.
3. Check ambient temperature sensor circuit. See «DTC B1412/12: AMBIENT AIR TEMPERATURE SENSOR CIRCUIT»(ref-99101-S07905106582001061800000) under SELF-DIAGNOSTICS.
4. Check driver side solar sensor circuit. See «DTC B1424/24: DRIVER SIDE SOLAR SENSOR CIRCUIT»(ref-99101-S00046889752001061800000) under SELF-DIAGNOSTICS.
5. Check passenger side solar sensor circuit. See «DTC B1421/21: PASSENGER SIDE SOLAR SENSOR CIRCUIT»(ref-99101-S04061707492001061800000) under SELF-DIAGNOSTICS.

Insufficient Airflow

Check front blower motor circuit. See BLOWER MOTOR CIRCUIT under SYSTEM TESTS.

No Cool Air Comes Out

1. Check front blower motor circuit. See «BLOWER MOTOR CIRCUIT»(ref-99101-S10101323542001061800000) under SYSTEM TESTS.
2. Check pressure sensor circuit. See «DTC B1423/23: PRESSURE SWITCH CIRCUIT»(ref-99101-S36179179752001061800000) under SELF-DIAGNOSTICS.
3. Check air mix door control servomotor circuit. See «AIR MIX DOOR SERVOMOTOR CIRCUIT»(ref-99101-S27164299692001061800000) under SYSTEM TESTS.
4. Check in-vehicle sensor circuit. See «DTC B1411/11: IN-VEHICLE TEMPERATURE SENSOR CIRCUIT»(ref-99101-S16966428252001061800000) under SELF-DIAGNOSTICS.
5. Check ambient temperature sensor circuit. See «DTC B1412/12: AMBIENT AIR TEMPERATURE SENSOR CIRCUIT»(ref-99101-S07905106582001061800000) under SELF-DIAGNOSTICS.
6. Check evaporator temperature sensor circuit. See «DTC B1413/13: EVAPORATOR TEMPERATURE SENSOR CIRCUIT»(ref-99101-S41773127942001061800000) under SELF-DIAGNOSTICS.
7. Check compressor lock sensor circuit. See «DTC B1422/22: COMPRESSOR LOCK SENSOR CIRCUIT»(ref-99101-S27358031102001061800000) under SELF-DIAGNOSTICS.
8. Check solenoid control valve changeable compressor circuit. See «DTC B1451/51: SOLENOID CONTROL VALVE CHANGEABLE COMPRESSOR CIRCUIT»(ref-99101-S26853249192001062600000) under SELF-DIAGNOSTICS.
9. Check back-up power source circuit. See «BACK-UP POWER SOURCE CIRCUIT»(ref-99101-S26741235632001061800000) under SYSTEM TESTS.

No Warm Air Comes Out

1. Check air mix door control servomotor circuit. See «AIR MIX DOOR SERVOMOTOR CIRCUIT»(ref-99101-S27164299692001061800000) under SYSTEM TESTS.
2. Check water valve control servomotor circuit. See «WATER VALVE CONTROL SERVOMOTOR CIRCUIT»(ref-99101-S09545988002001061800000) under SYSTEM TESTS.
3. Check in-vehicle sensor circuit. See «DTC B1411/11: IN-VEHICLE TEMPERATURE SENSOR CIRCUIT»(ref-99101-S16966428252001061800000) under SELF-DIAGNOSTICS.
4. Check ambient temperature sensor circuit. See «DTC B1412/12: AMBIENT AIR TEMPERATURE SENSOR CIRCUIT»(ref-99101-S07905106582001061800000) under SELF-DIAGNOSTICS.
5. Check evaporator temperature sensor circuit. See «DTC B1413/13: EVAPORATOR TEMPERATURE SENSOR CIRCUIT»(ref-99101-S41773127942001061800000) under SELF-DIAGNOSTICS.
6. Check compressor lock sensor circuit. See «DTC B1422/22: COMPRESSOR LOCK SENSOR CIRCUIT»(ref-99101-S27358031102001061800000) under SELF-DIAGNOSTICS.
7. Check solenoid control valve changeable compressor circuit. See «DTC B1451/51: SOLENOID CONTROL VALVE CHANGEABLE COMPRESSOR CIRCUIT»(ref-99101-S26853249192001062600000) under SELF-DIAGNOSTICS.
8. Check pressure sensor circuit. See «DTC B1423/23: PRESSURE SWITCH CIRCUIT»(ref-99101-S36179179752001061800000) under SELF-DIAGNOSTICS.
9. Check back-up power source circuit. See «BACK-UP POWER SOURCE CIRCUIT»(ref-99101-S26741235632001061800000) under SYSTEM TESTS.

Output Air Is Warmer Or Cooler Than Set Temperature Or Response Is Slow

1. Check air mix door control servomotor circuit. See «AIR MIX DOOR SERVOMOTOR CIRCUIT»(ref-99101-S27164299692001061800000) under SYSTEM TESTS.
2. Check water valve control servomotor circuit. See «WATER VALVE CONTROL SERVOMOTOR CIRCUIT»(ref-99101-S09545988002001061800000) under SYSTEM TESTS.
3. Check driver side air by-pass door control servomotor circuit. See «COOL AIR BY-PASS DOOR CONTROL SERVOMOTOR CIRCUIT»(ref-99101-S31537398602001062900000) under SYSTEM TESTS.
4. Check passenger side air by-pass door control servomotor circuit. See «COOL AIR BY-PASS DOOR CONTROL SERVOMOTOR CIRCUIT»(ref-99101-S31537398602001062900000) under SYSTEM TESTS.
5. Check driver side air by-pass door position sensor circuit. See «DTC B1434/34: DRIVER SIDE COOL AIR BY-PASS DOOR POSITION SENSOR CIRCUIT»(ref-99101-S26442156442001061800000) under SELF-DIAGNOSTICS.
6. Check passenger side air by-pass door position sensor circuit. See «DTC B1435/35: PASSENGER SIDE COOL AIR BY-PASS DOOR POSITION SENSOR CIRCUIT»(ref-99101-S10536227732001061800000) under SELF-DIAGNOSTICS.
7. Check in-vehicle sensor circuit. See «DTC B1411/11: IN-VEHICLE TEMPERATURE SENSOR CIRCUIT»(ref-99101-S16966428252001061800000) under SELF-DIAGNOSTICS.
8. Check ambient temperature sensor circuit. See «DTC B1412/12: AMBIENT AIR TEMPERATURE SENSOR CIRCUIT»(ref-99101-S07905106582001061800000) under SELF-DIAGNOSTICS.
9. Check evaporator temperature sensor circuit. See «DTC B1413/13: EVAPORATOR TEMPERATURE SENSOR CIRCUIT»(ref-99101-S41773127942001061800000) under SELF-DIAGNOSTICS.
10. Check driver side air duct temperature sensor circuit. See «DTC B1415/15: DRIVER SIDE AIR DUCT SENSOR CIRCUIT»(ref-99101-S15378828032001061800000) under SELF-DIAGNOSTICS.
11. Check passenger side air duct temperature sensor circuit. See «DTC B1416/16: PASSENGER SIDE AIR DUCT SENSOR CIRCUIT»(ref-99101-S23535766832001061800000) under SELF-DIAGNOSTICS.
12. Check driver side solar sensor circuit. See «DTC B1424/24: DRIVER SIDE SOLAR SENSOR CIRCUIT»(ref-99101-S00046889752001061800000) under SELF-DIAGNOSTICS.
13. Check passenger side solar sensor circuit. See «DTC B1421/21: PASSENGER SIDE SOLAR SENSOR CIRCUIT»(ref-99101-S04061707492001061800000) under SELF-DIAGNOSTICS.

No Maximum Cooling Or Maximum Warming Temperature Control

1. Check air mix door control servomotor circuit. See «AIR MIX DOOR SERVOMOTOR CIRCUIT»(ref-99101-S27164299692001061800000) under SYSTEM TESTS.
2. Check in-vehicle sensor circuit. See «DTC B1411/11: IN-VEHICLE TEMPERATURE SENSOR CIRCUIT»(ref-99101-S16966428252001061800000) under SELF-DIAGNOSTICS.
3. Check driver side air by-pass door control servomotor circuit. See «COOL AIR BY-PASS DOOR CONTROL SERVOMOTOR CIRCUIT»(ref-99101-S31537398602001062900000) .
4. Check passenger side air by-pass door control servomotor circuit. See «COOL AIR BY-PASS DOOR CONTROL SERVOMOTOR CIRCUIT»(ref-99101-S31537398602001062900000) .
5. Check evaporator temperature sensor circuit. See «DTC B1413/13: EVAPORATOR TEMPERATURE SENSOR CIRCUIT»(ref-99101-S41773127942001061800000) under SELF-DIAGNOSTICS.
6. Check driver side solar sensor circuit. See «DTC B1424/24: DRIVER SIDE SOLAR SENSOR CIRCUIT»(ref-99101-S00046889752001061800000) under SELF-DIAGNOSTICS.
7. Check passenger side solar sensor circuit. See «DTC B1421/21: PASSENGER SIDE SOLAR SENSOR CIRCUIT»(ref-99101-S04061707492001061800000) under SELF-DIAGNOSTICS.

No Air Inlet Control

1. Check air inlet door servomotor circuit. See «DTC B1442/42: AIR INLET DOOR SERVOMOTOR CIRCUIT»(ref-99101-S39122047172001061800000) under SELF-DIAGNOSTICS.
2. Check air inlet door position sensor circuit. See «DTC B1432/32 OR B1442/42: AIR INLET DOOR POSITION SENSOR CIRCUIT»(ref-99101-S12494456362001061800000) under SELF-DIAGNOSTICS.

No Airflow Mode Control

1. Check air vent mode door control servomotor circuit. See «AIR VENT MODE DOOR CONTROL SERVOMOTOR CIRCUIT»(ref-99101-S35796685762001061800000) under SYSTEM TESTS.
2. Check back-up power source circuit. See «BACK-UP POWER SOURCE CIRCUIT»(ref-99101-S26741235632001061800000) under SYSTEM TESTS.

A/C Indicator Blinking

1. Check compressor lock sensor circuit. See «DTC B1422/22: COMPRESSOR LOCK SENSOR CIRCUIT»(ref-99101-S27358031102001061800000) under SELF-DIAGNOSTICS.
2. Check solenoid control valve changeable compressor circuit. See «DTC B1451/51: SOLENOID CONTROL VALVE CHANGEABLE COMPRESSOR CIRCUIT»(ref-99101-S26853249192001062600000) under SELF-DIAGNOSTICS.

REAR A/C

Note. Rear A/C amplifier testing is not available from manufacturer.

Rear A/C System Does Not Operate

1. Temporarily substitute known-good rear A/C amplifier, then retest system.
2. Check ACC power source circuit. See «ACC POWER SOURCE CIRCUIT»(ref-99101-S32976624232001061800000) under SYSTEM TESTS.

No Rear Blower Motor Control

1. Check body ECU. See appropriate MULTIPLEX CONTROL SYSTEMS article in ACCESSORIES & EQUIPMENT.
2. Check rear blower motor circuit. See «BLOWER MOTOR CIRCUIT»(ref-99101-S10101323542001061800000) under SYSTEM TESTS.
3. Check rear blower motor resistor. See «BLOWER MOTOR CIRCUIT»(ref-99101-S10101323542001061800000) under SYSTEM TESTS.
4. Temporarily substitute known-good rear A/C amplifier, then retest system.
5. Check rear solar sensor circuit. See «DTC B1428/28: REAR SOLAR SENSOR CIRCUIT»(ref-99101-S12314715092001062600000) under SELF-DIAGNOSTICS.

Insufficient Rear Airflow

1. Check rear blower motor circuit. See «BLOWER MOTOR CIRCUIT»(ref-99101-S10101323542001061800000) under SYSTEM TESTS.
2. Check rear blower motor resistor. See «BLOWER MOTOR CIRCUIT»(ref-99101-S10101323542001061800000) under SYSTEM TESTS.

1. Check refrigerant charge volume. Discharge and charge A/C system, using approved refrigerant recovery/recycling equipment. Correct as necessary.
2. Ensure drive belt is properly installed. On a used drive belt, tensioner should be within "A" scale. Replace drive belt if it is outside of "A" scale. On a new drive belt, tensioner should be within "B" scale. see scheme 10
3. Check refrigerant pressures. Repair as necessary.
4. Check compressor circuit. See «COMPRESSOR CIRCUIT»(ref-99101-S41694110702001070300000) under SYSTEM TESTS.
5. Check pressure sensor circuit. See «DTC B1423/23: PRESSURE SWITCH CIRCUIT»(ref-99101-S36179179752001061800000) under SELF-DIAGNOSTICS.
6. Check rear door control servomotor. See «REAR DOOR CONTROL SERVOMOTOR CIRCUIT»(ref-99101-S23519680152001070300000) under SYSTEM TESTS.
7. Check ambient air temperature sensor circuit. See «DTC B1412/12: AMBIENT AIR TEMPERATURE SENSOR CIRCUIT»(ref-99101-S07905106582001061800000) under SELF-DIAGNOSTICS.
8. Temporarily substitute known-good rear A/C amplifier, then retest system.
9. Check rear solar sensor circuit. See «DTC B1428/28: REAR SOLAR SENSOR CIRCUIT»(ref-99101-S12314715092001062600000) under SELF-DIAGNOSTICS.

Indicator Check

1. Simultaneously press and hold AUTO and fresh/recirculated air switch. (Scheme 8) Turn ignition on. All indicators will flash 4 times, at one-second on and off intervals. A tone will sound when indicators flash. To cancel indicator check, press OFF switch.
2. After indicator check is complete, system will enter self-diagnostic mode. Stored diagnostic trouble codes will appear in sequence on driver side temperature display. See «DIAGNOSTIC TROUBLE CODE IDENTIFICATION»(ref-99101-S29990725932001061800000) table.
3. To slow rate at which codes are displayed, press driver side TEMP switch up arrow to change display to step operation. Each time temperature switch is pressed, display changes by one step.
4. If tone sounds as a code is displayed, problem currently exists. If tone does not sound as code is displayed, problem does not currently exist (history code). To exit self-diagnostics, press OFF switch.

DIAGNOSTIC TROUBLE CODE IDENTIFICATION

Actuator Check

1. Activate INDICATOR CHECK. See «INDICATOR CHECK»(ref-99101-S08658108512001062500000). When system enters self-diagnostic mode, press fresh/recirculated air switch. Each mode door, motor, and relay will operate at one-second intervals. Operation codes are displayed in order, starting with "0". To display codes one at a time, press driver side TEMP switch up arrow. Perform step-by-step actuator check.
2. Check airflow and temperature place by placing hand over appropriate duct. Tone will sound each time display code changes. Each display code is associated with a system operating condition. (Scheme 14) To cancel actuator check mode, press OFF switch.

Scheme 14

SYSTEM TESTS

A/C SYSTEM PERFORMANCE

1. Park vehicle out of direct sunlight. Connect manifold gauge set. Start engine and allow to idle at 2000 RPM. Set A/C controls to outside air, blower speed to high position, temperature control to cool position, A/C switch on and doors fully open (sun roof closed).
2. With intake air temperature about 86-95°F (30-35°C), refrigerant low-side pressure should be about 21-36 psi (1.5-2.5 kg/cm 2 ) and high-side pressure should be about 199-228 psi (14-16 kg/cm 2 ). Refrigerant pressures will vary slightly due to intake air temperatures.

ACC POWER SOURCE CIRCUIT

1. Remove A/C ECU, leaving harness connectors connected. See «A/C ELECTRONIC CONTROL UNIT»(ref-99101-S36801596042001061800000) under REMOVAL & INSTALLATION. Turn ignition to ACC position. Backprobe between A/C ECU connector terminal A11-3 (Gray wire) and ground. see scheme 8 See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000).
2. If battery voltage exists, no problem is indicated at this time. If battery voltage does not exist, turn ignition off. Check P-ACC fuse (7.5-amp), located in passenger side fuse 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 P-ACC fuse.

AIR MIX DOOR SERVOMOTOR CIRCUIT

1. Warm engine to normal operating temperature. Perform «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-99101-S02949575602001061800000) procedure under SELF-DIAGNOSTICS. After system enters self-diagnostic mode, perform «ACTUATOR CHECK»(ref-99101-S21025646672001061800000) under SELF-DIAGNOSTICS.
2. Press driver side TEMP up switch to enter step mode and display codes. See «AIR MIX DOOR AIRFLOW»(ref-99101-S19804935132001061800000) table. Air mix door operation should be as specified.
3. If air mix door functions as specified, no problem is indicated at this time. If air mix door does not function as specified, test air mix door servomotor. See «AIR MIX DOOR SERVOMOTOR»(ref-99101-S34424279862001061800000) under COMPONENT TESTS. Replace air mix door servomotor as necessary. If servomotor is okay, go to next step.
4. Check wiring harness and connectors between servomotor and A/C ECU. Repair as necessary. If wiring harness and connectors are okay, substitute known-good A/C ECU. Retest system.

AIR MIX DOOR AIRFLOW

AIR VENT MODE DOOR CONTROL SERVOMOTOR CIRCUIT

1. Warm engine to normal operating temperature. Perform «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-99101-S02949575602001061800000) procedure under SELF-DIAGNOSTICS. After system enters self-diagnostic mode, perform «ACTUATOR CHECK»(ref-99101-S21025646672001061800000) under SELF-DIAGNOSTICS.
2. Press TEMP up switch to enter step mode and display codes. See «AIR VENT MODE DOOR CONTROL SERVOMOTOR AIRFLOW OPERATION»(ref-99101-S00461312562001061800000) table. Servomotor door operation should be as specified.
3. If servomotor functions as specified, no problem is indicated at this time. If servomotor does not function as specified, test air vent mode door servomotor. See «AIR VENT MODE DOOR CONTROL SERVOMOTOR»(ref-99101-S26424154332001062800000) under COMPONENT TESTS. Replace air vent mode door servomotor as necessary. If servomotor is okay, go to next step.
4. Check wiring harness and connectors between servomotor and A/C ECU. Repair as necessary. If wiring harness and connectors are okay, substitute known-good A/C ECU. Retest system.

AIR VENT MODE DOOR CONTROL SERVOMOTOR AIRFLOW OPERATION

Front

1. Remove A/C ECU, leaving harness connectors connected. See «A/C ELECTRONIC CONTROL UNIT»(ref-99101-S36801596042001061800000) under REMOVAL & INSTALLATION. Backprobe between A/C ECU connector terminal A11-21 (White/Red wire) and ground. see scheme 8 See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000).
2. If battery voltage exists, no problem is indicated at this time. If battery voltage does not exist, check A/C fuse (7.5-amp) located in driver side junction block. If fuse is okay, check wiring harness and connectors between A/C ECU and battery. Repair wiring as necessary.

Rear

1. Remove A/C amplifier, leaving connectors connected. (Scheme 12)and see scheme 28. Backprobe and measure voltage between A/C amplifier connector terminal No. 3 (Blue/White wire) and ground.
2. If battery voltage exists, no problem is indicated at this time. If battery voltage does not exist, check RR ECU-B fuse (7.5-amp) located in trunk junction block. If fuse is okay, check wiring harness and connectors connected to RR ECU-B fuse (7.5-amp). Repair wiring as necessary.

Note. Blower motor speed is controlled by a duty ratio signal from A/C ECU. Blower motor speed increases as duty ratio increases.

1. Check HEATER fuse (50-amp), located in fusible link block in right rear of engine compartment. If fuse is blown, replace fuse and check for short in wiring harness and components connected to HEATER fuse. See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000) . Repair as necessary. If fuse is okay, go to next step.
2. Check wiring harness and connectors between blower motor and battery, and between blower motor and ground. Repair as necessary. If wiring is okay, check wiring harness and connectors between blower motor and A/C ECU. Repair as necessary.
3. If wiring harness and connectors are okay, replace blower motor. See «BLOWER MOTOR»(ref-99101-S39567948422001061800000) under REMOVAL & INSTALLATION. If problem still exists, substitute known-good A/C ECU. Retest system.

1. Remove trunk junction block ECU, located at left side of trunk. Leave harness connectors connected. Turn ignition on. Using rear A/C control panel, set rear blower motor speed to off, LO and HI. (Scheme 9)
2. Backprobe and measure voltage between trunk junction block ECU terminal L14-18 (Green/Orange wire) and ground, and between terminal L14-19 (Green/Black wire) and ground. See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000). (Scheme 15) See «CHECKING TRUNK J/B ECU & REAR A/C AMPLIFIER VOLTAGE»(ref-99101-S30011506642001063000000) table. If voltage is not as specified, go to next step. If voltage is as specified, go to step 6.
3. Remove rear A/C amplifier with harness connector connected. (Scheme 12)and see scheme 28. Turn ignition on. Set rear blower motor switch to specified positions. Backprobe rear A/C amplifier connector.
4. Measure voltage between ground and A/C amplifier connector terminal No. 16 (Green/Orange wire). Measure voltage between ground and terminal No. 11 (Green/Black wire), if not equipped with rear cooler box or terminal No. 15 (Green/Black wire), if equipped with rear cooler box. (Scheme 16) See «CHECKING TRUNK J/B ECU & REAR A/C AMPLIFIER VOLTAGE»(ref-99101-S30011506642001063000000) table. CHECKING TRUNK J/B ECU & REAR A/C AMPLIFIER VOLTAGE Blower Motor Switch Position Voltage (1) Voltage (2) Off Zero Zero LO 10-14 Zero HI 10-14 10-14 (1) Voltage measured between trunk junction block ECU connector terminal L14-18 (Green/Orange wire) and ground. (Scheme 15) Voltage measured between A/C amplifier connector terminal No. 16 (Green/Orange wire) and ground. (Scheme 16) (2) Voltage measured between trunk junction block ECU connector terminal L14-19 (Green/Black wire) and ground. (Scheme 15) If not equipped with rear cooler, voltage measured between A/C amplifier connector terminal No. 11 (Green/Black wire) and ground. If equipped with rear cooler, voltage measured between A/C amplifier connector terminal No. 15 (Green/Black wire) and ground. (Scheme 16)
5. If voltage is not as specified, go to next step. If voltage is as specified, check harness and connectors between A/C amplifier and trunk junction block ECU. Repair as necessary. If harness and connectors are okay, replace trunk junction block ECU. Retest system.
6. Remove rear A/C amplifier with harness connector connected. (Scheme 12)and see scheme 28. Turn ignition on. Set rear blower motor switch to specified positions. Backprobe rear A/C amplifier connector.
7. Measure voltage between ground and A/C amplifier connector terminals No. 1 (Yellow wire), No. 2 (White/Yellow wire), and No. 8 (Blue/Red wire). (Scheme 16) See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000). See «CHECKING REAR A/C AMPLIFIER VOLTAGE»(ref-99101-S33673033972001070200000) table. CHECKING REAR A/C AMPLIFIER VOLTAGE Blower Motor Switch Position Voltage (1) Voltage (2) (3) Voltage Off Zero Zero Zero LO 10-14 Less Than One 10-14 HI 10-14 10-14 Less Than One (1) Voltage measured between A/C amplifier connector terminal No. 8 (Blue/Red wire) and ground. (Scheme 16) (2) Voltage measured between A/C amplifier connector terminal No. 1 (Yellow wire) and ground. (Scheme 16) (3) Voltage measured between A/C amplifier connector terminal No. 2 (White/Yellow wire) and ground. (Scheme 16)
8. If voltage is as specified, go to step 10. If voltage is not as specified, check rear blower motor resistor. See «BLOWER MOTOR RESISTOR»(ref-99101-S20500490192001070200000) under COMPONENT TESTS.
9. If blower motor resistor is okay, check wiring harness and connectors between blower motor resistor and rear A/C amplifier. Repair as necessary. If harness and connectors are okay, replace trunk junction block ECU. Retest system.
10. Remove blower motor. See «BLOWER MOTOR»(ref-99101-S39567948422001061800000) under REMOVAL & INSTALLATION. Check rear blower motor operation. See «BLOWER MOTOR»(ref-99101-S05681287752001070200000) under COMPONENT TESTS.
11. If blower motor is okay, check wiring harness and connectors between blower motor, blower motor resistor and ground connections. Repair as necessary. If wiring harness and connectors are okay, replace A/C amplifier. Retest system.

Scheme 15

Scheme 16

CENTER VENT SWING REGISTER CIRCUIT

1. Remove A/C ECU, leaving harness connectors connected. See «A/C ELECTRONIC CONTROL UNIT»(ref-99101-S36801596042001061800000) under REMOVAL & INSTALLATION. Turn ignition on.
2. Set mode selector switch to face or bi-level. Measure voltage between A/C ECU terminal A12-24 (Red/Green wire) and ground. If battery voltage is present, go to next step. If battery voltage is not present, check swing register step motor. See «CENTER VENT SWING REGISTER STEP MOTOR»(ref-99101-S42314699372001070500000) under COMPONENT TESTS.
3. If center vent swing register step motor is okay, check wiring harness and connectors between center vent swing register and A/C ECU. See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000) . Replace A/C ECU if wiring harness and connectors are okay. Retest system.

COMPRESSOR CIRCUIT

1. Access Engine Control Module (ECM), located behind passenger's side kick panel. Leave harness connectors connected. Turn ignition on.
2. Start engine and push AUTO switch. Backprobe and measure voltage ECM connector between terminal E3-16 (White wire) and ground. see scheme 9 Turn A/C switch on and off. When A/C switch is on, voltage should be 10.0-14.0 volts and zero volts when switch is off.
3. If voltage is not as specified, check compressor clutch relay. See «COMPRESSOR CLUTCH RELAY»(ref-99101-S28233203402001061800000) under COMPONENT TESTS. Replace clutch relay if necessary. If compressor clutch relay is okay, check compressor magnetic clutch. See «COMPRESSOR MAGNETIC CLUTCH»(ref-99101-S07952572542001070300000) under COMPONENT TESTS.
4. If compressor magnetic clutch is okay, check wiring harness and connectors between compressor clutch relay and ECM. Repair as necessary. If wiring harness is okay, check wiring harness and connector between ECM and compressor. Repair as necessary. If wiring harness is okay, check and replace ECM and/or A/C ECU. Retest system.

Driver Side

1. Perform «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-99101-S02949575602001061800000) procedure under SELF-DIAGNOSTICS. After system enters self-diagnostic mode, perform «ACTUATOR CHECK»(ref-99101-S21025646672001061800000) under SELF-DIAGNOSTICS. Press driver side TEMP switch up switch to enter step mode and display codes.
2. Press up switch in order and check operation of water valve (located in engine compartment). See «COOL AIR BY-PASS DOOR CONTROL SERVOMOTOR»(ref-99101-S04139763172001062900000) table. Cool air by-pass door position should change with change in temperature display. (Scheme 21)
3. If cool air by-pass door operates as described, go to next symptom check within symptom list. See «SYMPTOM TESTS»(ref-99101-S14647607732001062800000). If cool air by-pass door does not operate as specified, check cool air by-pass door control servomotor. See «COOL AIR BY-PASS DOOR CONTROL SERVOMOTOR»(ref-99101-S35474436202001061800000) under COMPONENT TESTS.
4. If servomotor is okay, check wiring harness and connectors between servomotor and A/C ECU. Repair as necessary. If wiring is okay, replace A/C ECU. Retest system.

COOL AIR BY-PASS DOOR CONTROL SERVOMOTOR

Passenger Side

1. Perform «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-99101-S02949575602001061800000) procedure under SELF-DIAGNOSTICS. After system enters self-diagnostic mode, perform «ACTUATOR CHECK»(ref-99101-S21025646672001061800000) under SELF-DIAGNOSTICS. Press driver side TEMP switch up switch to enter step mode and display codes.
2. Press up switch in order and check operation of water valve (located in engine compartment). See «COOL AIR BY-PASS DOOR CONTROL SERVOMOTOR»(ref-99101-S04139763172001062900000) table. Cool air by-pass door position should change with change in temperature display. (Scheme 22)
3. If cool air by-pass door operates as described, go to next symptom check within symptom list. See «SYMPTOM TESTS»(ref-99101-S14647607732001062800000). If cool air by-pass door does not operate as specified, check cool air by-pass door control servomotor. See «COOL AIR BY-PASS DOOR CONTROL SERVOMOTOR»(ref-99101-S35474436202001061800000) under COMPONENT TESTS.
4. If servomotor is okay, check wiring harness and connectors between servomotor and A/C ECU. Repair as necessary. If wiring is okay, replace A/C ECU. Retest system.

Cooling Fan On-Vehicle Check

1. Turn ignition on and engine off. With coolant temperature less than 180°F (82°C), cooling fan should be off.
2. Start engine and allow to idle. Turn A/C off. With coolant temperature less than 180°F (82°C), cooling fan should be off.
3. With engine idling. Turn A/C on. With coolant temperature less than 180°F (82°C), cooling fan should operate at low speed.
4. With engine idling. Disconnect engine coolant temperature sensor connector. With A/C on and coolant temperature less than 180°F (82°C), cooling fan should operate at high speed. If fan does not operate as specified, check cooling fan operation. See «COOLING FAN OPERATIONAL CHECK»(ref-99101-S24764846802001061800000) .

Engine Coolant Temperature Sensor Check

Remove Engine Coolant Temperature (ECT) sensor, located under throttle body. Place ECT sensor and thermometer in ice water. Measure ECT sensor resistance between sensor terminals at various temperatures. See ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE table. Replace ECT sensor if resistance is not approximately value specified.

ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE

Cooling Fan Relay Check

1. Remove cooling fan relay from fusible link block located at right rear of engine compartment. Check continuity between relay terminals. Continuity should exist between terminals No. 1 and 2, and not between terminals No. 3 and 5. (Scheme 17)
2. Using a fused jumper wire, apply battery voltage to relay terminal No. 1 and ground terminal No. 2. Continuity should exist between terminals No. 3 and 5. Replace cooling fan relay if continuity is not as specified.

Scheme 17

1. Remove A/C ECU, leaving harness connectors connected. See «A/C ELECTRONIC CONTROL UNIT»(ref-99101-S36801596042001061800000) under REMOVAL & INSTALLATION. Turn ignition on. Backprobe between A/C ECU terminals A11-9 (Light Green/Red wire) and A11-1 (White/Black wire). see scheme 8 See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000).
2. If battery voltage exists, no problem is indicated at this time. If battery voltage does not exist, turn ignition off. Check continuity between A/C ECU terminal A11-1 (White/Black wire) and ground. If continuity exists, go to next step. If continuity does not exist, repair wiring between A/C ECU and ground connection.
3. Check P-IG fuse (7.5-amp), located in passenger side fuse 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 P-IG fuse.

1. Remove A/C amplifier, leaving harness connector connected. Turn ignition on. Backprobe and measure voltage between A/C amplifier connector terminals No. 6 (White/Black wire) and No. 10 (Black/Red wire). (Scheme 16) See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000).
2. If battery voltage exists, no problem is indicated at this time. If battery voltage does not exist, turn ignition off. Check continuity between A/C amplifier connector terminal No. 6 (White/Black wire) and ground. If continuity exists, go to next step. If continuity does not exist, repair wiring between A/C amplifier and ground connection.
3. Check RR fuse (7.5-amp) located in trunk junction block. If fuse is okay, repair wiring harness between A/C amplifier and battery. If fuse is not okay, repair wiring harness between fuse and components connected to RR fuse. See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000).

IGNITOR CIRCUIT

For ignitor circuit diagnosis, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

REAR DOOR CONTROL SERVOMOTOR CIRCUIT

1. Warm engine to normal operating temperature. Perform «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-99101-S02949575602001061800000) procedure under SELF-DIAGNOSTICS. After system enters self-diagnostic mode, perform «ACTUATOR CHECK»(ref-99101-S21025646672001061800000) under SELF-DIAGNOSTICS.
2. Press driver side TEMP switch up arrow to display codes one at a time. Check rear door control servomotor operation. See «REAR DOOR CONTROL SERVOMOTOR OPERATION CODES»(ref-99101-S15405341032001070300000) table. If rear door control servomotor operation is as specified, go to next step.
3. Remove trunk junction block ECU, located at left side of trunk. Leave harness connectors connected. Turn ignition on. Operate front A/C control panel fresh air mode switch. Backprobe and measure voltage between trunk junction block terminal L14-20 (Gray/Blue wire) and ground. (Scheme 15)
4. If voltage is not 10.0-14.0 volts, go to next step. If voltage is 10.0-14.0 volts, check rear door control servomotor operation. See «REAR DOOR CONTROL SERVOMOTOR»(ref-99101-S33228483242001070300000) under COMPONENT TESTS. If servomotor is okay, go to step 8. Replace rear door control servomotor if operation is not as specified.
5. Remove A/C amplifier, leaving harness connector connected. Turn ignition on. Operate front A/C control panel fresh air mode switch. Backprobe and measure voltage between A/C amplifier connector terminal No. 4 (Violet wire) and ground.
6. If voltage is less that one volt, go to next step. If voltage is more than one volt, check rear door control servomotor operation. See «REAR DOOR CONTROL SERVOMOTOR»(ref-99101-S33228483242001070300000) under COMPONENT TESTS. If servomotor is okay, go to step 8. Replace rear door control servomotor if operation is not as specified.
7. Check wiring harness between A/C amplifier and trunk junction block ECU. Repair harness as necessary. If harness is okay, replace trunk junction block ECU. Retest system.
8. Check wiring harness between A/C amplifier and rear door control servomotor and ground connection. Repair harness as necessary. If harness is okay, replace A/C amplifier. Retest stem.

REAR DOOR CONTROL SERVOMOTOR OPERATION CODES

REAR EXPANSION VALVE MAGNETIC CONTROL CIRCUIT

1. Remove trunk junction block ECU, located at left side of trunk. Leave harness connectors connected. Turn ignition on. Turn rear A/C on. Backprobe and measure voltage between trunk junction block ECU terminal L14-11 (Green/Yellow wire) and ground. (Scheme 15) See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000).
2. If voltage is less than one volt, go to next step. If voltage is more than one volt, check rear expansion valve magnetic control. See «REAR EXPANSION VALVE MAGNETIC CONTROL»(ref-99101-S32672048112001070500000) under COMPONENT TESTS. Repair as necessary.
3. Remove A/C amplifier, leaving harness connector connected. Turn ignition on. Turn rear A/C on. Backprobe A/C amplifier connector terminal No. 5 (Green/Yellow wire) and ground. (Scheme 16) See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000).
4. If voltage is less than one volt, go to next step. If voltage is more than one volt, check Green/Yellow wire between expansion valve magnetic control connector terminal No. 1 and A/C amplifier connector terminal No. 5. See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000). Repair as necessary. If Green/Yellow wire is okay, go to next step.
5. Check Black/Red wire between expansion valve magnetic control connector terminal No. 2 and A/C amplifier connector terminal No. 10. If Black/Red wire is okay, replace A/C amplifier.

REAR SMOKE SENSOR CIRCUIT

1. Remove trunk junction block ECU, located at left side of trunk. Leave harness connectors connected. Turn ignition on. Turn rear A/C to AUTO mode. Position a lit cigarette over rear air intake. Backprobe and measure voltage between trunk junction block ECU terminal L14-16 (Pink/Green wire) and ground. (Scheme 15) See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000).
2. If voltage is more than 4.0 volts, go to next step. If voltage is less than 4.0 volts, check smoke sensor. See «SMOKE SENSOR»(ref-99101-S16002329202001070500000) under REMOVAL & INSTALLATION.
3. If smoke sensor is okay, check wiring harness between smoke sensor and trunk junction block ECU. Repair as necessary. If wiring harness is okay, go to next step.
4. Check wiring harness between smoke sensor, ground connection and A/C amplifier. If wiring harness is okay, replace trunk junction block ECU. Retest system.

WATER VALVE CONTROL SERVOMOTOR CIRCUIT

1. Perform «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-99101-S02949575602001061800000) procedure under SELF-DIAGNOSTICS. After system enters self-diagnostic mode, perform «ACTUATOR CHECK»(ref-99101-S21025646672001061800000) under SELF-DIAGNOSTICS. Press driver side TEMP switch up switch to enter step mode and display codes.
2. Press up switch in order and check operation of water valve (located in engine compartment). See «WATER VALVE CONTROL SERVOMOTOR»(ref-99101-S21105207632001062900000) table. Water valve position should change with change in temperature display.
3. If water valve operates as described, go to next symptom check within symptom list. See «SYMPTOM TESTS»(ref-99101-S14647607732001062800000) . If water valve does not operate as specified, check water valve servomotor. See «WATER VALVE CONTROL SERVOMOTOR»(ref-99101-S36110598632001062900000) under COMPONENT TESTS.

WATER VALVE CONTROL SERVOMOTOR

AMBIENT AIR TEMPERATURE SENSOR

Remove radiator grille. Disconnect ambient air temperature sensor connector. Measure resistance between sensor terminals while heating sensor with a heat gun. See AMBIENT AIR TEMPERATURE SENSOR SPECIFICATIONS table. Replace sensor if resistance is not as specified.

AMBIENT AIR TEMPERATURE SENSOR SPECIFICATIONS

AIR INLET DOOR POSITION SENSOR

1. Remove blower unit. See «BLOWER UNIT»(ref-99101-S14985704362001061800000) under REMOVAL & INSTALLATION. Remove A/C ECU. Disconnect air inlet servomotor connector and remove servomotor.
2. Measure resistance between air inlet servomotor connector terminals No. 1 (Red/White wire) and No. 2 (White/Black wire). (Scheme 18) If resistance is 4200-7800 ohms, go to next step. If resistance is not 4200-7800 ohms, replace air inlet servomotor.
3. Using a fused jumper wire, apply battery voltage to air inlet servomotor connector terminal No. 4 (Green/Yellow wire). Connect terminal No. 5 (Green/Red wire) to ground. Lever should move smoothly to recirculated air position. Reverse power and ground connections. Lever should move smoothly to fresh air position.
4. As air inlet servomotor operates, measure resistance at each door position between terminals No. 2 (White/Black wire) and No. 3 (Black/Yellow wire). Resistance should be as specified for each door position. See «AIR INLET DOOR POSITION SENSOR SPECIFICATIONS»(ref-99101-S07700705812001061800000) table. If resistance is not as specified or servomotor does not operate smoothly, replace air inlet door servomotor.

AIR INLET DOOR POSITION SENSOR SPECIFICATIONS

Scheme 18

AIR INLET DOOR SERVOMOTOR

1. Remove blower unit. See «BLOWER UNIT»(ref-99101-S14985704362001061800000) under REMOVAL & INSTALLATION. Disconnect air inlet servomotor connector and remove servomotor.
2. Using a fused jumper wire, apply battery voltage to air inlet servomotor connector terminal No. 4 (Green/Yellow wire). Connect terminal No. 5 (Green/Red wire) to ground. (Scheme 18)
3. Lever should move smoothly to recirculated air position. Reverse power and ground connections. Lever should move smoothly to fresh air position. If lever does not operate as specified, replace servomotor.

AIR MIX DOOR SERVOMOTOR

Remove air mix door servomotor. See AIR MIX DOOR SERVOMOTOR under REMOVAL & INSTALLATION. Disconnect air mix servomotor connector. Connect ohmmeter positive lead to servomotor terminal No. 3 and negative lead to specified terminals. Measure resistance between servomotor terminal No. 3 and terminals No. 1, 2, 4 and 5. (Scheme 19) Replace air mix door servomotor if resistance is not 16-18 ohms between specified terminals.

Scheme 19

AIR VENT MODE DOOR CONTROL SERVOMOTOR

Remove air vent mode door servomotor. See AIR VENT MODE DOOR SERVOMOTOR under REMOVAL & INSTALLATION. Disconnect air mix servomotor connector. Connect ohmmeter positive lead to servomotor terminal No. 3 and negative lead to other terminals. Measure resistance between servomotor terminal No. 3 and terminals No. 1, 2, 4 and 5. (Scheme 19) Replace air mix door servomotor if resistance is not 16-18 ohms between specified terminals.

Blower motor testing is not available from manufacturer. See BLOWER MOTOR CIRCUIT under SYSTEM TESTS.

Remove rear blower motor. See REAR A/C COOLING UNIT under REMOVAL & INSTALLATION. Using a fused jumper wire, connect battery voltage to blower motor terminal No. 1 (Blue/Red wire). Connect battery ground to blower motor terminal No. 3 (White/Black wire). If blower motor operates smoothly, check wiring harness and connectors between blower motor, blower motor resistor and ground connections. Repair as necessary. Replace blower motor if it does not operate smoothly.

1. Remove rear blower motor resistor. See «REAR A/C COOLING UNIT»(ref-99101-S29163365472001070200000) under REMOVAL & INSTALLATION.
2. Measure resistor resistance between terminals No. 1 (Yellow wire) and No. 3 (White/Yellow wire), and terminals No. 2 (Blue/Red wire) and No. 3 (White/Yellow wire). See «WIRING DIAGRAMS»(ref-99101-S32973477022001061800000) . See «CHECKING REAR BLOWER MOTOR RESISTOR RESISTANCE»(ref-99101-S02436149862001070200000) table.
3. If resistance is as specified, check wiring harness and connectors between blower motor resistor and rear A/C amplifier. Repair as necessary. Replace blower motor resistor if resistance is not as specified.

CHECKING REAR BLOWER MOTOR RESISTOR RESISTANCE

COMPRESSOR CLUTCH RELAY

1. Remove compressor clutch relay. Relay is located in engine compartment junction block. Check resistance between relay terminals. Resistance between terminals No. 1 and 2 should be 62.5-90.9 ohms. (Scheme 20) Continuity should not exist between terminals No. 3 and 5.
2. Using a fused jumper wire, apply battery voltage to relay terminal No. 1. Connect terminal No. 2 to ground. Continuity should exist between terminals No. 3 and 5. If continuity is not as specified, replace compressor clutch relay.

Scheme 20

COMPRESSOR MAGNETIC CLUTCH

Disconnect compressor magnetic clutch connector. Using a fused jumper wire, connect battery voltage to magnetic clutch connector terminal No. 3 (Black/White wire). Replace magnetic clutch if it is not energized.

COMPRESSOR LOCK SENSOR

Raise and support vehicle. Remove engine undercover. Disconnect compressor lock sensor connector. Measure resistance between sensor terminals No. 1 (Blue/White wire) and No. 2 (Brown wire). If resistance is not 160-320 ohms at 68°F (20°C), replace compressor lock sensor.

1. Remove cool air by-pass door servomotor. See «COOL AIR BY-PASS DOOR SERVOMOTOR»(ref-99101-S06502392032001062700000) under REMOVAL & INSTALLATION. Disconnect cool air by-pass door servomotor connector.
2. Measure resistance between servomotor connector terminals No. 1 (Red wire) and No. 2 (White/Blue wire). (Scheme 21) If resistance is 4200-7200 ohms, go to next step. If resistance is not 4200-7200 ohms, replace cool air by-pass door servomotor.
3. Using a fused jumper wire, apply battery voltage to servomotor connector terminal No. 5 (Green/Red wire). Connect terminal No. 4 (Gray wire) to ground. Lever should move smoothly to shut position. Reverse power and ground connections. Lever should move smoothly to open position. (Scheme 21)
4. As servomotor operates, measure resistance at each lever position between terminals No. 2 (White/Blue wire) and No. 3 (Black/Red wire). Resistance should be as specified for each lever position. See «COOL AIR BY-PASS DOOR POSITION SENSOR SPECIFICATIONS»(ref-99101-S42755503352001061800000) table. If resistance is not as specified or servomotor does not operate smoothly, replace cool air by-pass door servomotor.

Scheme 21

1. Remove cool air by-pass door servomotor. See «COOL AIR BY-PASS DOOR SERVOMOTOR»(ref-99101-S06502392032001062700000) under REMOVAL & INSTALLATION. Disconnect cool air by-pass door servomotor connector.
2. Measure resistance between servomotor connector terminals No. 1 (Red/White wire) and No. 2 (White/Black wire). (Scheme 22) If resistance is 4200-7200 ohms, go to next step. If resistance is not 4200-7200 ohms, replace cool air by-pass door servomotor.
3. Using a fused jumper wire, apply battery voltage to servomotor connector terminal No. 5 (Green/Orange wire). Connect terminal No. 4 (Green/Black wire) to ground. Lever should move smoothly to shut position. Reverse power and ground connections. Lever should move smoothly to open position. (Scheme 22)
4. As servomotor operates, measure resistance at each lever position between terminals No. 2 (White/Black wire) and No. 3 (Black/Blue wire). Resistance should be as specified for each lever position. See «COOL AIR BY-PASS DOOR POSITION SENSOR SPECIFICATIONS»(ref-99101-S42755503352001061800000) table. If resistance is not as specified or servomotor does not operate smoothly, replace cool air by-pass door servomotor.

COOL AIR BY-PASS DOOR POSITION SENSOR SPECIFICATIONS

Scheme 22

1. Remove cool air by-pass door servomotor. See «COOL AIR BY-PASS DOOR SERVOMOTOR»(ref-99101-S06502392032001062700000) under REMOVAL & INSTALLATION. Disconnect cool air by-pass door servomotor connector.
2. Using a fused jumper wire, apply battery voltage to servomotor terminal No. 5 (Gray/Red wire). Connect terminal No. 4 (Gray wire) to ground. Lever should move smoothly to shut position. (Scheme 21)
3. Reverse power and ground position. Lever should move smoothly to open position. If servomotor does not operate or does not operate smoothly, replace cool air by-pass door servomotor.

1. Remove cool air by-pass door servomotor. See «COOL AIR BY-PASS DOOR SERVOMOTOR»(ref-99101-S06502392032001062700000) under REMOVAL & INSTALLATION. Disconnect cool air by-pass door servomotor connector.
2. Using a fused jumper wire, apply battery voltage to servomotor connector terminal No. 5 (Green/Orange wire). Connect terminal No. 4 (Green/Black wire) to ground. (Scheme 22)
3. Lever should move smoothly to shut position. Reverse power and ground connections. Lever should move smoothly to open position. If servomotor does not operate or does not operate smoothly, replace cool air by-pass door servomotor.

DUCT TEMPERATURE SENSORS

Remove suspect duct sensor. See DUCT SENSORS under REMOVAL & INSTALLATION. Remove appropriate sensor for testing. Measure resistance between sensor terminals at specified temperatures. See DUCT TEMPERATURE SENSOR RESISTANCE SPECIFICATIONS table. If resistance is not as specified, replace sensor.

DUCT TEMPERATURE SENSOR RESISTANCE SPECIFICATIONS

EVAPORATOR TEMPERATURE SENSOR

Remove evaporator temperature sensor. See EVAPORATOR TEMPERATURE SENSOR under REMOVAL & INSTALLATION. Measure resistance between sensor terminals at specified temperatures. See EVAPORATOR TEMPERATURE SENSOR SPECIFICATIONS table. If resistance is not as specified, replace sensor.

EVAPORATOR TEMPERATURE SENSOR SPECIFICATIONS

HC & CO Circuit

Remove exhaust gas sensor located on front radiator support, next to horn. Using a fused jumper wire, connect battery voltage to exhaust sensor terminal No. 3 (Light Green/Red wire) and battery negative to terminal No. 6 (White/Black wire). (Scheme 23) Apply voltage for more than 30 seconds, then measure resistance between terminals No. 1 (Yellow wire) and No. 2 (Brown/Red wire). Resistance should be 5-100 k/ohms at 50-95°F (10-35°C). When exhaust gas sensor is exposed to exhaust gases, resistance should decrease. If resistance is not as specified, replace sensor.

NOx Circuit

Remove exhaust gas sensor located on front radiator support, next to horn. Using a fused jumper wire, connect battery voltage to exhaust sensor terminal No. 3 (Light Green/Red wire) and battery negative to terminal No. 6 (White/Black wire). (Scheme 23) Apply voltage for more than 120 seconds, then measure resistance between terminals No. 1 (Yellow wire) and No. 4 (Blue/Black wire). Resistance should be 1-100 k/ohms at 50-95°F (10-35°C). When exhaust gas sensor is exposed to exhaust gases, resistance should increase. If resistance is not as specified, replace sensor.

Scheme 23

IN-VEHICLE TEMPERATURE SENSOR

Remove left instrument panel undercover. Disconnect in-vehicle temperature sensor. Measure resistance between in-vehicle temperature sensor terminals while heating sensor with a heat gun. See IN-VEHICLE TEMPERATURE SENSOR SPECIFICATIONS table. If resistance is not as specified, replace sensor.

IN-VEHICLE TEMPERATURE SENSOR SPECIFICATIONS

PRESSURE SWITCH

1. Pressure switch is located on liquid line, next to high-pressure charging port, in front of condenser. (Scheme 24) Install manifold gauge set. Disconnect pressure switch connector.
2. Connect positive lead from three, 1.5-volt dry cell batteries to switch terminal No. 3. Connect negative lead to switch terminal No. 1. Measure voltage between pressure switch terminals No. 1 and 2. (Scheme 24)
3. Voltage should be 1.0-4.8 volts with refrigerant pressure of 57-463 psi (4.0-32.5 kg/cm 2 ). If voltage is not as specified, replace pressure switch.

Scheme 24

REAR DOOR CONTROL SERVOMOTOR

1. Remove rear door control servomotor. See «REAR DOOR CONTROL SERVOMOTOR»(ref-99101-S17002749252001070300000) under REMOVAL & INSTALLATION.
2. Using a fused jumper wire, connect battery voltage to servomotor terminal No. 7. Connect battery ground to terminal No. 8. (Scheme 25) Connect specified servomotor terminals, in turn, to ground. Servomotor lever should move smoothly to specified positions. See «TESTING REAR DOOR CONTROL SERVOMOTOR»(ref-99101-S40457473232001070300000) table. Replace rear door control servomotor if operation is not as specified.

TESTING REAR DOOR CONTROL SERVOMOTOR

Scheme 25

REAR EXPANSION VALVE MAGNETIC CONTROL

1. Remove rear expansion valve. See «REAR A/C COOLING UNIT»(ref-99101-S29163365472001070200000) under REMOVAL & INSTALLATION. Using a fused jumper wire, apply battery voltage and ground to expansion valve magnetic control connectors. Check air passage with battery voltage applied and removed.
2. When battery voltage is applied, air passage should be open. When battery voltage is removed, air passage should be closed. Replace expansion valve magnetic control if operation is not as specified.
3. If operation of expansion valve magnetic control is as specified, check wiring harness between magnetic control and trunk junction block ECU. Repair as necessary. If wiring harness is okay, replace trunk junction block ECU.

REAR SOLAR SENSOR

1. Using a flat-blade screwdriver with tip taped, remove solar sensor. Disconnect solar sensor harness connector. Cover sensor with cloth. Connect voltmeter positive lead to rear solar sensor terminal No. 1 (Gray wire) and negative lead to sensor terminal No. 2 (White/Blue wire). Cover sensor with a cloth and measure voltage between terminals. Voltage should be less than one volt.
2. Remove cloth. Subject sensor to a bright light and measure voltage. Voltage should be about 0.4 volt. As light intensity decreases, voltage should increase. If voltage is not as specified, replace sensor.

SMOKE SENSOR

Note. Smoke sensor detects smoke using light, check sensor in the dark.

1. Remove smoke sensor. See «REAR A/C COOLING UNIT»(ref-99101-S29163365472001070200000) under REMOVAL & INSTALLATION. Using a fused jumper wire, apply battery voltage to smoke sensor connector terminal No. 3 (Black/Red wire). Connect smoke sensor connector terminal No. 1 (White/Black wire) to battery ground. (Scheme 26)
2. Position a lit cigarette below smoke sensor air intake. Measure voltage between sensor terminals No. 1 (White/Black wire) and No. 2 (Blue/Yellow wire). With no smoke present, voltage should be less than one volt. With smoke present, voltage should be more than 4.0 volts. Replace rear smoke sensor if voltage is not as specified.

Scheme 26

SOLENOID OF EXTERNALLY CHANGEABLE COMPRESSOR

Raise and support vehicle. Remove engine undercover. Disconnect solenoid of externally changeable compressor 2-pin connector. Measure resistance between solenoid terminals No. 1 and 2. Resistance should be 10-11 ohms at 68°F (20°C). If resistance is not 10-11 ohms, replace A/C compressor. See A/C COMPRESSOR under REMOVAL & INSTALLATION.

CENTER VENT SWING REGISTER STEP MOTOR

Note. Swing register terminals No. 1, 2, 6 and 7 are for passenger side. Terminals No. 3, 4, 5 and 10 are for driver side. Terminal No. 8 is not used.

Remove center vent swing register from instrument panel. Measure swing register resistance with ohmmeter positive lead at terminal No. 9. (Scheme 27) Resistance measured between swing register terminal No. 9 and terminals No. 1, 2, 3, 4, 5, 6, 7 and 10 should be 279-321 ohms. Replace center vent swing register if resistance is not as specified.

Scheme 27

WATER VALVE CONTROL SERVOMOTOR

1. Remove blower unit. See «BLOWER UNIT»(ref-99101-S14985704362001061800000) under REMOVAL & INSTALLATION. Disconnect water valve servomotor connector. Disconnect water valve control cable and remove servomotor.
2. Using a fused jumper wire, connect battery voltage to servomotor terminal No. 1 (Green wire). Connect terminal No. 3 (Orange wire) to ground. (Scheme 28) Servomotor lever should move smoothly to open position.
3. Using fused jumper wire, connect battery voltage to servomotor terminal No. 2 (Green/White wire). Connect terminal No. 1 (Green wire) to ground. Servomotor lever should move smoothly to shut position. If servomotor does not operate or does not operate smoothly, replace water valve control servomotor.
4. If water valve control servomotor operates as specified, check wiring harness and connectors between servomotor and A/C ECU. Repair as necessary. If wiring is okay, replace A/C ECU. Retest system operation.

Scheme 28

HEATER CORE

Note. It is not necessary to remove front A/C-heater unit to replace heater core.

RECEIVER-DRIER

Note. DO NOT remove drier bag from vinyl bag until ready to insert into modulator tank.