Air Conditioning System (Diagnostic Codes & Circuit Tests): Overview Lexus CT I

DESCRIPTION

The room temperature sensor is installed in the instrument panel. It detects the cabin temperature to control air conditioning AUTO mode. The resistance of the room temperature sensor changes in accordance with the cabin temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

The air conditioning amplifier assembly applies voltage (5 V) to the room temperature sensor and reads voltage changes as the resistance of the room temperature sensor changes. This sensor also sends appropriate signals to the air conditioning amplifier assembly.

Scheme 117

The ambient temperature sensor is installed in front of the condenser. It detects the ambient temperature to control air conditioning AUTO mode. This sensor is connected to the air conditioning amplifier assembly and detects fluctuations in the ambient temperature. This data is used for controlling the cabin temperature. The sensor sends a signal to the air conditioning amplifier assembly. The resistance of the ambient temperature sensor changes in accordance with the ambient temperature. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

The air conditioning amplifier assembly applies voltage (5 V) to the ambient temperature sensor and reads voltage changes as the resistance of the ambient temperature sensor changes.

Scheme 118

The evaporator temperature sensor is installed on the evaporator in the air conditioning unit to detect the cooled air temperature that has passed through the evaporator and to control the air conditioning. It sends appropriate signals to the air conditioning amplifier assembly. The resistance of the evaporator temperature sensor changes in accordance with the cooled air temperature that has passed through the evaporator. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

The air conditioning amplifier assembly applies voltage (5 V) to the evaporator temperature sensor and reads voltage changes as the resistance of the evaporator temperature sensor changes. This sensor is used for frost prevention.

Scheme 119

Scheme 120

1. READ VALUE USING TECHSTREAM Connect the Techstream to the DLC3. Turn the power switch on (IG). Turn the Techstream on. Enter the following menus: Body Electrical / Air Conditioner / Data List. Check the value(s) by referring to the table below. AIR CONDITIONER Tester Display Measurement Item/Range Normal Condition Diagnostic Note Evaporator Fin Thermistor Evaporator temperature sensor / Min.: -29.7°C (-21.46°F) Max.: 59.55°C (139.19°F) Actual evaporator temperature displayed - OK The display is as specified in the Normal Condition column. Result Result Proceed to NG A OK (When troubleshooting according to Problem Symptoms Table) B OK (When troubleshooting according to the DTC) C B --> See step 5 C --> See step 4 A: Go to next step
2. INSPECT EVAPORATOR TEMPERATURE SENSOR Remove the evaporator temperature sensor. Disconnect the e2 evaporator temperature sensor connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition e2-1 - e2-2 -10°C (14°F) 7.30 to 9.10 kohms e2-1 - e2-2 -5°C (23°F) 5.65 to 6.95 kohms e2-1 - e2-2 0°C (32°F) 4.40 to 5.35 kohms e2-1 - e2-2 5°C (41°F) 3.40 to 4.15 kohms e2-1 - e2-2 10°C (50°F) 2.70 to 3.25 kohms e2-1 - e2-2 15°C (59°F) 2.14 to 2.58 kohms e2-1 - e2-2 20°C (68°F) 1.71 to 2.05 kohms e2-1 - e2-2 25°C (77°F) 1.38 to 1.64 kohms e2-1 - e2-2 30°C (86°F) 1.11 to 1.32 kohms NOTE: Hold the sensor only by its connector. Touching the sensor may change the resistance value. When measuring, the sensor temperature must be the same as the ambient temperature. HINT: As the temperature increases, the resistance decreases (see the graph (Scheme 120) ). TEXT IN ILLUSTRATION *a Component without harness connected (Evaporator Temperature Sensor) *b Sensing Portion *c Resistance (kohms) *d Allowable Range *e Temperature (°C (°F)) NG --> See step 7 OK: Go to next step
3. INSPECT AIR CONDITIONING HARNESS ASSEMBLY (AIR CONDITIONING AMPLIFIER - EVAPORATOR TEMPERATURE SENSOR) Remove the air conditioning harness assembly. Refer to «DISASSEMBLY»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information). Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition z1-6 (TEA) - e2-2 Always Below 1 ohms z1-5 (SGA) - e2-1 Always Below 1 ohms z1-6 (TEA) - Body ground Always 10 kohms or higher z1-5 (SGA) - Body ground Always 10 kohms or higher NG --> See step 8 OK --> See step 6
4. REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)
5. PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to «PROBLEM SYMPTOMS TABLE»(ref-568603-S01769296392013072300000)
6. REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)
7. REPLACE EVAPORATOR TEMPERATURE SENSOR. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)
8. REPLACE AIR CONDITIONING HARNESS ASSEMBLY. Refer to «DISASSEMBLY»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)

This DTC is stored when refrigerant pressure on the high pressure side is extremely low (190 kPa (1.9 kgf/cm 2 , 28 psi) or less) or extremely high (3140 kPa (32.0 kgf/cm 2 , 455 psi) or more). The air conditioning pressure sensor is installed on the high pressure line. It detects refrigerant pressure to output a refrigerant pressure signal to the air conditioning amplifier assembly. The air conditioning amplifier assembly converts this signal to a pressure value according to the sensor characteristics to control the compressor.

Scheme 121

Scheme 122

Scheme 123

Scheme 124

1. CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT) Disconnect the A30 air conditioning pressure sensor connector. Measure the voltage according to the value(s) in the table below. Standard Voltage Tester Connection Switch Condition Specified Condition A30-3 (+) - Body ground Power switch on (IG) 4.75 to 5.25 V NG --> See step 5 OK: Go to next step
2. CHECK HARNESS AND CONNECTOR (GROUND CIRCUIT) Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition A30-1 (-) - Body ground Always Below 1 ohms NG --> See step 6 OK: Go to next step
3. INSPECT AIR CONDITIONING PRESSURE SENSOR (SENSOR SIGNAL CIRCUIT) Reconnect the A30 air conditioning pressure sensor connector. Remove the air conditioning amplifier assembly with the connectors still connected. Measure the voltage according to the value(s) in the table below. Standard Voltage Tester Connection Condition Specified Condition H85-9 (PRE) - Body ground Power switch on (IG) (A/C switch: off) 0.73 to 4.84 V HINT: If the voltage is not as specified, there may be a malfunction in the air conditioning amplifier assembly, A/C pressure sensor or wire harness. It is also possible that the amount of refrigerant may not be appropriate. TEXT IN ILLUSTRATION *a Component with harness connected (Air Conditioning Amplifier Assembly) NG --> See step 7 OK: Go to next step
4. INSPECT AIR CONDITIONING PRESSURE SENSOR (SENSOR SIGNAL CIRCUIT) Measure the voltage when the following conditions are met: Item Condition Vehicle Doors Fully open Compressor speed 5200 rpm Temperature Setting MAX COLD Blower Speed HI A/C Switch on R/F Switch RECIRCULATION Interior Temperature 25 to 35°C (77 to 95°F) NOTE: If refrigerant pressure in the high pressure line becomes extremely high during the inspection (if the voltage exceeds 4.84 V), the fail-safe function stops compressor operation. Therefore, measure the voltage before the fail-safe function operates. It is necessary to measure the voltage over a period of time (approximately 10 minutes) because the problem symptom may recur after a while. HINT: When the outside air temperature is low (below -1.5°C (29.3°F)), the compressor stops due to signals from the ambient temperature sensor and the evaporator temperature sensor to prevent the evaporator from freezing. In this case, perform the inspection in a warm indoor environment. Measure the voltage according to the value(s) in the table below. Standard Voltage Tester Connection Condition Specified Condition H85-9 (PRE) - Body ground Power switch on (IG) (A/C: on) 0.73 to 4.84 V Result Result Proceed to OK (When troubleshooting according to the DTC) A OK (When troubleshooting according to Problem Symptoms Table) B NG C TEXT IN ILLUSTRATION *a Component with harness connected (Air Conditioning Amplifier Assembly) B --> See step 21 C --> See step 13 A --> See step 22
5. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - A/C PRESSURE SENSOR) Disconnect the H85 air conditioning amplifier assembly connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition A30-3 (+) - H85-10 (S5-3) Always Below 1 ohms H85-10 (S5-3) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> See step 22
6. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - A/C PRESSURE SENSOR) Disconnect the H85 air conditioning amplifier assembly connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition A30-1 (-) - H85-13 (SG-2) Always Below 1 ohms H85-13 (SG-2) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> See step 22
7. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - A/C PRESSURE SENSOR) Disconnect the H85 air conditioning amplifier assembly connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition A30-2 (PR) - H85-9 (PRE) Always Below 1 ohms A30-2 (PR) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
8. CHECK FOR A/C SYSTEM LEAK Install the manifold gauge set. Recover the refrigerant from the A/C system using a refrigerant recovery unit. Evacuate the A/C system and check that vacuum can be maintained. OK Vacuum can be maintained in the A/C system. HINT: If vacuum cannot be maintained in the A/C system, there may be a refrigerant leak. In this case, it is necessary to repair or replace the leaking part of the A/C system. NG --> See step 12 OK: Go to next step
9. CHARGE REFRIGERANT Add an appropriate amount of refrigerant. Refer to «REPLACEMENT»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information) . NEXT: Go to next step
10. RECHECK FOR DTC Recheck for the DTC when the following conditions are met: Item Condition Vehicle Doors Fully open Compressor Speed 5200 rpm Temperature Setting MAX COLD Blower Speed HI A/C Switch on R/F Switch RECIRCULATION Interior Temperature 25 to 35°C (77 to 95°F) NOTE: If refrigerant pressure in the high pressure line is excessive, this DTC will be stored. Therefore, it is necessary to measure the voltage over a period of time (approximately 10 minutes) because this DTC may be stored after the A/C has been operating for a while. HINT: When the outside air temperature is low (below -1.5°C (29.3°F)), the compressor stops due to signals from the ambient temperature sensor and the evaporator temperature sensor to prevent the evaporator from freezing. In this case, perform the inspection in a warm indoor environment. Result Result Proceed to DTC B1423/23 is output A DTC B1423/23 is not output B NOTE: If the DTC was stored due to an insufficient or excessive amount of refrigerant, the problem may have been solved after performing the previous step. However, the root cause of insufficient refrigerant may be refrigerant leaks. The root cause of excessive refrigerant may be adding refrigerant when the level was insufficient. Therefore, identify and repair any refrigerant leaks as necessary. B --> END A: Go to next step
11. INSPECT AIR CONDITIONING PRESSURE SENSOR Install the manifold gauge set. Reconnect the air conditioning pressure sensor connector. Turn the power switch on (IG). Measure the voltage according to the value(s) in the table below. Standard Voltage Tester Connection Condition Specified Condition H85-9 (PRE) - H85-13 (SG-2) Refrigerant pressure: Normal pressure (less than 3187 kPa (32.5 kgf/cm 2 , 462 psi) and more than 390 kPa (4.0 kgf/cm 2 , 57 psi)) 0.73 to 4.84 V HINT: The A/C pressure sensor power source voltage is 5 V. TEXT IN ILLUSTRATION *a Component with harness connected (Air Conditioning Amplifier Assembly) *b Voltage (V) *c kPa (kgf/cm 2 , psi) NG --> See step 19 OK --> See step 22
12. REPAIR A/C SYSTEM LEAK Identify the area where refrigerant leaks from. Refer to «REPLACEMENT»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information) . Repair the identified area of the A/C system. Evacuate the A/C system. NEXT --> See step 23
13. INSPECT COOLING FAN SYSTEM Check that the cooling fan(s) operates normally. HINT: Refer to Cooling Fan Circuit. Refer to «ON-VEHICLE INSPECTION»(ref-568758-S36172857642013072300000) . NG --> REPAIR COOLING FAN SYSTEM OK: Go to next step
14. CHARGE REFRIGERANT Use a refrigerant recovery unit to recover refrigerant. Evacuate the A/C system. Add an appropriate amount of refrigerant. Refer to «REPLACEMENT»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information) . HINT: If refrigerant is added and the system has not been properly evacuated (insufficient vacuum time), moisture in the air remaining in the system will freeze in the expansion valve, blocking the flow on the high pressure side. Therefore, recover the refrigerant and properly evacuate the system. Add an appropriate amount of refrigerant, and check for DTCs. NEXT: Go to next step
15. RECHECK FOR DTC Recheck for the DTC when the following conditions are met: Item Condition Vehicle Doors Fully open Compressor Speed 5200 rpm Temperature Setting MAX COLD Blower Speed HI A/C Switch on R/F Switch RECIRCULATION Interior Temperature 25 to 35°C (77 to 95°F) NOTE: If refrigerant pressure in the high pressure line is excessive, this DTC will be stored. Therefore, it is necessary to measure the voltage over a period of time (approximately 10 minutes) because DTC may be stored after the A/C has been operating for a while. HINT: When the outside air temperature is low (below -1.5°C (29.3°F)), the compressor stops due to signals from the ambient temperature sensor and the evaporator temperature sensor to prevent the evaporator from freezing. In this case, perform the inspection in a warm indoor environment. If refrigerant is added and the system has not been properly evacuated (insufficient vacuum time), moisture in the air remaining in the system will freeze in the expansion valve, blocking the flow on the high pressure side. Therefore, recover the refrigerant and properly evacuate the system. Add an appropriate amount of refrigerant, and check for the DTC. If the DTC is not output, it indicates that the cooler dryer in the condenser is not able to absorb moisture in the refrigerant. In this case, to complete the repair, it is necessary to replace the cooler dryer. Result Result Proceed to DTC B1423/23 is output A DTC B1423/23 is not output B B --> See step 25 A: Go to next step
16. REPLACE EXPANSION VALVE Replace the expansion valve with a new or a known good one. Refer to «DISASSEMBLY»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information) . HINT: Replace the expansion valve with a new or a known good one because the expansion valve is either stuck or clogged. NEXT: Go to next step
17. CHARGE REFRIGERANT Add an appropriate amount of refrigerant. Refer to «REPLACEMENT»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information) . NEXT: Go to next step
18. RECHECK FOR DTC Recheck for the DTC when the following conditions are met: Item Condition Vehicle Doors Fully open Compressor Speed 5200 rpm Temperature Setting MAX COLD Blower Speed HI A/C Switch on R/F Switch RECIRCULATION Interior Temperature 25 to 35°C (77 to 95°F) NOTE: If refrigerant pressure in the high pressure line is excessive, this DTC will be stored. Therefore, it is necessary to measure the voltage over a period of time (approximately 10 minutes) because this DTC may be stored after the A/C has been operating for a while. HINT: When the outside air temperature is low (below -1.5°C (29.3°F)), the compressor stops due to signals from the ambient temperature sensor and the evaporator temperature sensor to prevent the evaporator from freezing. In this case, perform the inspection in a warm indoor environment. If refrigerant pressure is not normal after replacing the expansion valve with a new or a known good one, the condenser or pipes may be clogged with dirt, dust or other contaminants. In this case, clean or replace the condenser or pipes. Result Result Proceed to DTC B1423/23 is not output A DTC B1423/23 is output B B --> See step 24 A --> END
19. REPLACE AIR CONDITIONING PRESSURE SENSOR Replace the air conditioning pressure sensor. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information) . HINT: Since the air conditioning pressure sensor cannot be inspected while it is removed from the vehicle, replace the air conditioning pressure sensor with a new or a known good one and check that the condition returns to normal. NEXT: Go to next step
20. RECHECK FOR DTC Recheck for the DTC when the following conditions are met: Item Condition Vehicle Doors Fully open Compressor Speed 5200 rpm Temperature Setting MAX COLD Blower Speed HI A/C Switch on R/F Switch RECIRCULATION Interior Temperature 25 to 35°C (77 to 95°F) NOTE: If refrigerant pressure in the high pressure line is excessive, this DTC will be stored. Therefore, it is necessary to measure the voltage over a period of time (approximately 10 minutes) because this DTC may be stored after the A/C has been operating for a while. HINT: When the outside air temperature is low (below -1.5°C (29.3°F)), the compressor stops due to signals from the ambient temperature sensor and the evaporator temperature sensor to prevent the evaporator from freezing. In this case, perform the inspection in a warm indoor environment. Result Result Proceed to DTC B1423/23 is not output A DTC B1423/23 is output B B --> See step 22 A --> END
21. PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to «PROBLEM SYMPTOMS TABLE»(ref-568603-S01769296392013072300000)
22. REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)
23. CHARGE REFRIGERANT. Refer to «REPLACEMENT»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)
24. REPLACE CONDENSER ASSEMBLY. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)
25. REPLACE COOLER DRYER. Refer to «DISASSEMBLY»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)

The air mix control servo motor (for front passenger side) sends pulse signals to indicate the damper position to the air conditioning amplifier assembly. The air conditioning amplifier assembly activates the motor (normal or reverse) based on these signals to move the air mix control servo motor (for front passenger side) to any position. As a result, the amount of air passing through the heater core after passing through the evaporator is adjusted, and the temperature of the air blowing toward the passenger side is controlled.

The air conditioning amplifier assembly communicates with the servo through a communication/driver IC and wiring assembly called the air conditioning harness assembly.

HINT

Confirm that no mechanical problem is present because this DTC can be stored when either a damper link or the damper is mechanically locked.

Scheme 125

The air inlet control servo motor sends pulse signals to indicate the damper position to the air conditioning amplifier assembly. The air conditioning amplifier assembly activates the motor (normal or reverse) based on these signals to move the air inlet mode selection air inlet control damper to any position, which controls the intake air settings (FRESH, FRESH/RECIRCULATION, and RECIRCULATION).

The air conditioning amplifier assembly communicates with the servo through a communication/driver IC and wiring assembly called the air conditioning harness assembly.

HINT

Confirm that no mechanical problem is present because this DTC can be stored when either a damper link or the damper is mechanically locked.

Scheme 126

The air outlet control servo motor sends pulse signals to indicate the damper position to the air conditioning amplifier assembly. The air conditioning amplifier assembly activates the motor (normal or reverse) based on these signals to move the air outlet control servo motor to any position, which controls the air outlet switching.

The air conditioning amplifier assembly communicates with the servo through a communication/driver IC and wiring assembly called the air conditioning harness assembly.

HINT

Confirm that no mechanical problem is present because this DTC can be stored when either a damper link or the damper is mechanically locked.

Scheme 127

The air mix control servo motor (for driver side) sends pulse signals to indicate the damper position to the air conditioning amplifier assembly. The air conditioning amplifier assembly activates the motor (normal or reverse) based on these signals to move the air mix control servo motor (for driver side) to any position. As a result, the amount of air passing through the heater core after passing through the evaporator is adjusted, and the temperature of the air blowing toward the driver side is controlled.

The air conditioning amplifier assembly communicates with the servo through a communication/driver IC and wiring assembly called the air conditioning harness assembly.

HINT

Confirm that no mechanical problem is present because this DTC can be stored when either a damper link or the damper is mechanically locked.

Scheme 128

The A/C inverter assembly monitors the voltage of the battery. It stops compressor control and stores the DTC when the monitored voltage is outside the specified range.

The output DTC is memorized as previous trouble. Compressor control may not resume unless the power switch is turned off.

Scheme 129

The inverter in the compressor with motor assembly outputs high-voltage to operate the motor. If there is an open or short in the output circuit, the ECU will stop compressor operation and store the DTC. The DTC will be stored as a history DTC. The compressor operation remains stopped until both the history and current DTCs are cleared.

The inverter activation signal is sent to the compressor with motor assembly from the power management control ECU. Compressor control is stopped and the DTC is stored if there is an open or short in the signal circuit.

Scheme 130

The temperature sensor of the compressor with motor assembly detects its inverter temperature.

If the temperature exceeds the maximum, the compressor with motor assembly stops compressor operation, and this DTC will be stored.

The compressor with motor assembly stops compressor control and outputs this DTC if the rotation load is too large or too small while controlling motor rotation in the compressor with motor assembly.

Possible causes are refrigerant gas leakage, overcharged refrigerant gas, insufficient cooling because of a condenser fan circuit malfunction, or compressor lock.

The compressor with motor assembly monitors the control power voltage in the circuit. It stops the compressor circuit and stores the DTC when the monitored voltage is outside the specified range.

The output DTC is memorized as previous trouble. Compressor control may not resume unless the power switch is turned off.

The air conditioning harness assembly connects the air conditioning amplifier assembly and the servo motors. The air conditioning amplifier assembly supplies power and sends operation instructions to each servo motor through the air conditioning harness assembly. Each servo motor sends damper position information to the air conditioning amplifier assembly.

Scheme 131

The power management control ECU and compressor with motor assembly transmit information to one another via a communication line. Compressor control is stopped and the DTC is stored if communication information is cut off or abnormal information occurs.

The DTC is also detected if high-voltage power supplied from the inverter with converter assembly to the compressor control circuit is shut off.

The output DTC is memorized as previous trouble.

Scheme 132

The automatic light control sensor (solar sensor) is installed on the upper side of the instrument panel. It detects sunlight to control air conditioning AUTO mode. The output voltage from the automatic light control sensor (solar sensor) varies in accordance with the amount of sunlight. When the amount of sunlight increases, the output voltage increases. As the sunlight decreases, the output voltage decreases. The air conditioning amplifier assembly detects changes in the output voltage from the automatic light control sensor (solar sensor).

Scheme 133

The air conditioning amplifier assembly detects the windshield glass surface temperature from this circuit. The air conditioning amplifier assembly applies voltage to the air conditioning thermistor assembly (glass temperature sensor). As the windshield glass surface temperature rises, the resistance decreases. The air conditioning amplifier assembly detects the resistance change as the windshield glass surface temperature changes.

HINT

The whole air conditioning thermistor assembly should be replaced if the glass temperature sensor is malfunctioning.

Scheme 134

Scheme 135

1. READ VALUE USING TECHSTREAM Connect the Techstream to the DLC3. Turn the power switch on (IG). Turn the Techstream on. Enter the following menus: Body Electrical / Air Conditioner / Data List. Check the value(s) by referring to the table below. AIR CONDITIONER Tester Display Measurement Item/Range Normal Condition Diagnostic Note Glass Temperature Glass temperature/ Min.: -327.68°C (-557.82°F) Max.: 327.67°C (621.81°F) Actual glass temperature displayed - OK The display is as specified in the Normal Condition column. NG --> See step 2 OK --> See step 4
2. INSPECT AIR CONDITIONING THERMISTOR ASSEMBLY (GLASS TEMPERATURE SENSOR) Remove the air conditioning thermistor assembly (glass temperature sensor). Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition T11-1 (SEG3) - T11-4 (TFG) 10°C (50°F) 5.92 to 6.09 kohms T11-1 (SEG3) - T11-4 (TFG) 15°C (59°F) 4.94 to 5.07 kohms T11-1 (SEG3) - T11-4 (TFG) 20°C (68°F) 4.20 to 4.29 kohms T11-1 (SEG3) - T11-4 (TFG) 25°C (77°F) 3.64 to 3.70 kohms T11-1 (SEG3) - T11-4 (TFG) 30°C (86°F) 3.19 to 3.26 kohms T11-1 (SEG3) - T11-4 (TFG) 35°C (95°F) 2.85 to 2.91 kohms T11-1 (SEG3) - T11-4 (TFG) 40°C (104°F) 2.58 to 2.64 kohms T11-1 (SEG3) - T11-4 (TFG) 45°C (113°F) 2.37 to 2.43 kohms T11-1 (SEG3) - T11-4 (TFG) 50°C (122°F) 2.21 to 2.26 kohms T11-1 (SEG3) - T11-4 (TFG) 55°C (131°F) 2.07 to 2.12 kohms T11-1 (SEG3) - T11-4 (TFG) 60°C (140°F) 1.97 to 2.01 kohms NOTE: Hold the sensor only by its connector. Touching the sensor may change the resistance value. When measuring, the sensor temperature must be the same as the ambient temperature. TEXT IN ILLUSTRATION *a Heat Conduction Sheet Part *b Component without harness connected (Air Conditioning Thermistor Assembly (Glass Temperature Sensor)) *c Resistance (kohms) *d Temperature (°C (°F)) NG --> See step 5 OK: Go to next step
3. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - GLASS TEMPERATURE SENSOR) Disconnect the T11 air conditioning thermistor assembly (glass temperature sensor) connector. Disconnect the H86 air conditioning amplifier assembly connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition T11-4 (TFG) - H86-15 (TFG) Always Below 1 ohms T11-4 (TFG) - Body ground Always 10 kohms or higher T11-1 (SEG3) - H86-7 (LBLO) Always Below 1 ohms T11-1 (SEG3) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> See step 4
4. REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)
5. REPLACE AIR CONDITIONING THERMISTOR ASSEMBLY. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)

The air conditioning amplifier assembly detects the temperature of the area near the windshield glass using this circuit. The air conditioning amplifier assembly applies voltage to the air conditioning thermistor assembly (glass surroundings temperature sensor). As the temperature of the area near the windshield glass rises, the resistance decreases. The air conditioning amplifier assembly detects the resistance change as the windshield glass surroundings temperature changes.

HINT

The whole air conditioning thermistor assembly should be replaced if the glass surroundings temperature sensor is malfunctioning.

Scheme 136

Scheme 137

1. READ VALUE USING TECHSTREAM Connect the Techstream to the DLC3. Turn the power switch on (IG). Turn the Techstream on. Enter the following menus: Body Electrical / Air Conditioner / Data List. Check the value(s) by referring to the table below. AIR CONDITIONER Tester Display Measurement Item/Range Normal Condition Diagnostic Note Glass Surroundings Temperature Glass surroundings temperature/ Min.: -327.68°C (-557.82°F) Max.: 327.67°C (621.81°F) Actual glass surroundings temperature displayed - OK The display is as specified in the Normal Condition column. NG --> See step 2 OK --> See step 4
2. INSPECT AIR CONDITIONING THERMISTOR ASSEMBLY (GLASS SURROUNDINGS TEMPERATURE SENSOR) Remove the air conditioning thermistor assembly (glass surroundings temperature sensor). Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition T11-1 (SEG3) - T11-2 (TNG) 10°C (50°F) 5.92 to 6.09 kohms T11-1 (SEG3) - T11-2 (TNG) 15°C (59°F) 4.94 to 5.07 kohms T11-1 (SEG3) - T11-2 (TNG) 20°C (68°F) 4.20 to 4.29 kohms T11-1 (SEG3) - T11-2 (TNG) 25°C (77°F) 3.64 to 3.70 kohms T11-1 (SEG3) - T11-2 (TNG) 30°C (86°F) 3.19 to 3.26 kohms T11-1 (SEG3) - T11-2 (TNG) 35°C (95°F) 2.85 to 2.91 kohms T11-1 (SEG3) - T11-2 (TNG) 40°C (104°F) 2.58 to 2.64 kohms T11-1 (SEG3) - T11-2 (TNG) 45°C (113°F) 2.37 to 2.43 kohms T11-1 (SEG3) - T11-2 (TNG) 50°C (122°F) 2.21 to 2.26 kohms T11-1 (SEG3) - T11-2 (TNG) 55°C (131°F) 2.07 to 2.12 kohms T11-1 (SEG3) - T11-2 (TNG) 60°C (140°F) 1.97 to 2.01 kohms NOTE: Hold the sensor only by its connector. Touching the sensor may change the resistance value. When measuring, the sensor temperature must be the same as the ambient temperature. TEXT IN ILLUSTRATION *a Heat Conduction Sheet Part *b Component without harness connected (Air Conditioning Thermistor Assembly (Glass Surroundings Temperature Sensor)) *c Resistance (kohms) *d Temperature (°C (°F)) NG --> See step 5 OK: Go to next step
3. CHECK HARNESS AND CONNECTOR (A/C AMPLIFIER - GLASS SURROUNDINGS TEMPERATURE SENSOR) Disconnect the T11 air conditioning thermistor assembly (glass surroundings temperature sensor) connector. Disconnect the H86 air conditioning amplifier assembly connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition T11-2 (TNG) - H86-16 (TNG) Always Below 1 ohms T11-2 (TNG) - Body ground Always 10 kohms or higher T11-1 (SEG3) - H86-7 (LBLO) Always Below 1 ohms T11-1 (SEG3) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> See step 4
4. REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)
5. REPLACE AIR CONDITIONING THERMISTOR ASSEMBLY. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)

The air conditioning amplifier assembly detects the windshield glass humidity from this circuit. The air conditioning amplifier assembly applies voltage to the air conditioning thermistor assembly (glass humidity sensor). As the humidity rises, the voltage output of the sensor increases. The air conditioning amplifier assembly detects the voltage change as the humidity changes.

HINT

The whole air conditioning thermistor assembly should be replaced if the glass humidity sensor is malfunctioning.

Scheme 138

Scheme 139

Scheme 140

1. READ VALUE USING TECHSTREAM Connect the Techstream to the DLC3. Turn the power switch on (IG). Turn the Techstream on. Enter the following menus: Body Electrical / Air Conditioner / Data List. Check the value(s) by referring to the table below. AIR CONDITIONER Tester Display Measurement Item/Range Normal Condition Diagnostic Note Glass Humidity Glass humidity/ Min.: 0 (%) Max.: 100 (%) Actual glass humidity displayed - OK The display is as specified in the Normal Condition column. NG --> See step 2 OK --> See step 6
2. INSPECT AIR CONDITIONING AMPLIFIER ASSEMBLY Disconnect the T11 air conditioning thermistor assembly (glass humidity sensor) connector. Measure the voltage according to the value(s) in the table below. Standard Voltage Tester Connection Condition Specified Condition T11-5 (S5V) - Body ground Power switch on (IG) 4.5 to 5.5 V TEXT IN ILLUSTRATION *a Front view of wire harness connector (to Air Conditioning Thermistor Assembly (Glass Humidity Sensor)) NG --> See step 5 OK: Go to next step
3. INSPECT AIR CONDITIONING THERMISTOR ASSEMBLY (GLASS HUMIDITY SENSOR) Remove the air conditioning thermistor assembly (glass humidity sensor) with the connector still connected. Turn the power switch on (IG). Measure the voltage according to the value(s) in the table below. Standard Voltage Tester Connection Condition Specified Condition T11-1 (SEG3) - T11-3 (RH) Power switch on (IG) Humidity is 5 to 15% Approximately 1.01 V T11-1 (SEG3) - T11-3 (RH) Power switch on (IG) Humidity is 15 to 25% Approximately 1.37 V T11-1 (SEG3) - T11-3 (RH) Power switch on (IG) Humidity is 25 to 35% Approximately 1.73 V T11-1 (SEG3) - T11-3 (RH) Power switch on (IG) Humidity is 35 to 45% Approximately 2.09 V T11-1 (SEG3) - T11-3 (RH) Power switch on (IG) Humidity is 45 to 55% Approximately 2.45 V T11-1 (SEG3) - T11-3 (RH) Power switch on (IG) Humidity is 55 to 65% Approximately 2.81 V T11-1 (SEG3) - T11-3 (RH) Power switch on (IG) Humidity is 65 to 75% Approximately 3.17 V T11-1 (SEG3) - T11-3 (RH) Power switch on (IG) Humidity is 75 to 85% Approximately 3.53 V T11-1 (SEG3) - T11-3 (RH) Power switch on (IG) Humidity is 85 to 95% Approximately 3.89 V NOTE: Do not touch the sensor as body heat will affect the inspection results. When performing the inspection, hold the sensor by its connector. Allow the sensor to acclimate to the ambient temperature and humidity before performing the inspection. The specified voltages in the table above are based on inspections performed when the ambient temperature is 25°C (77°F). HINT: As the humidity increases, the voltage increases (see the graph (Scheme 140) ). TEXT IN ILLUSTRATION *a Heat Conduction Sheet Part *b Component with harness connected (Air Conditioning Thermistor Assembly (Glass Humidity Sensor)) *c Voltage (V) *d Relative Humidity (%) NG --> See step 7 OK: Go to next step
4. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - GLASS HUMIDITY SENSOR) Disconnect the T11 air conditioning thermistor assembly (glass humidity sensor) connector. Disconnect the H85 and H86 air conditioning amplifier assembly connectors. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition T11-3 (RH) - H85-28 (RH) Always Below 1 ohms T11-3 (RH) - Body ground Always 10 kohms or higher T11-1 (SEG3) - H86-7 (LBLO) Always Below 1 ohms T11-1 (SEG3) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> See step 6
5. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - GLASS HUMIDITY SENSOR) Disconnect the T11 air conditioning thermistor assembly (glass humidity sensor) connector. Disconnect the H85 air conditioning amplifier assembly connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition T11-5 (S5V) - H85-31 (S5-4) Always Below 1 ohms T11-5 (S5V) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> See step 6
6. REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)
7. REPLACE AIR CONDITIONING THERMISTOR ASSEMBLY. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)

The DTC is stored if there is insulation trouble with the high-voltage circuit in the air conditioning system. Possible causes are poor insulation in the compressor with motor assembly, or mixing of any oil other than ND-OIL 11 in the refrigerant cycle.

A high-voltage motor is built into the electrical compressor and is cooled directly with refrigerant. Compressor oil (ND-OIL 11) with high insulation performance is used because a leakage of electrical power may occur if regular compressor oil (ND-OIL 8) is used.

Scheme 141

w/ Navigation System

1. Center cluster module circuit (air conditioning control assembly) switch signals are sent to the air conditioning amplifier assembly via LIN communication. The air conditioning amplifier assembly then sends these signals to the navigation computer sub-assembly*1 or display and navigation module display*2 via CAN communication.
2. *1: w/ Navigation system (for HDD)
3. *2: w/ Navigation system (for DVD)

w/o Navigation System

1. Center cluster module circuit (air conditioning control assembly) switch signals are sent to the air conditioning amplifier assembly via LIN communication.

Scheme 142

Scheme 143

1. w/ Navigation System
2. w/o Navigation System

The blower with fan motor sub-assembly (blower motor) is operated by signals from the air conditioning amplifier assembly. Blower motor speed signals are transmitted in accordance with changes in the duty ratio.

Scheme 144

The PTC heater assembly is installed in the heater radiator unit and operates when engine coolant temperature is low and normal heater effectiveness is insufficient.

The A/C control assembly switches the circuit in the PTC relay and operates the PTC heater assembly when the operating conditions (cooling water temperature is below 65°C (149°F), setting temperature is MAX. HOT, ambient temperature is below 10°C (50°F) and blower switch is not OFF) are met.

The number of circuits operated in the PTC heater is controlled according to the overall electric load of the vehicle and charging system output (DC-DC converter built into inverter with converter assembly). therefore, troubleshooting should be performed with other electrical components turned off.

Scheme 145

Scheme 146

1. INSPECT PTC HEATER ASSEMBLY Remove the PTC heater assembly. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition A17-3 (B) - A18-2 (E) Always Below 1 ohms A17-2 (B) - A18-2 (E) Always Below 1 ohms A17-2 (B) - A18-1 (E) Always Below 1 ohms A17-1 (B) - A18-1 (E) Always Below 1 ohms TEXT IN ILLUSTRATION *a Component without harness connected (PTC Heater Assembly) NG --> See step 7 OK: Go to next step
2. CHECK HARNESS AND CONNECTOR (PTC HEATER ASSEMBLY - BODY GROUND) Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition A18-1 (E) - Body ground Always Below 1 ohms A18-2 (E) - Body ground Always Below 1 ohms NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
3. CHECK HARNESS AND CONNECTOR (PTC HEATER ASSEMBLY - NO. 1 INTEGRATION RELAY) Disconnect the PTC heater assembly connector. Disconnect the engine room relay block and junction block (No. 1 integration relay) connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition A17-1 (B) - 1H-10 (PTC1) Always Below 1 ohms A17-2 (B) - 1H-6 (PTC2) Always Below 1 ohms A17-3 (B) - 1H-9 (PTC3) Always Below 1 ohms A17-1 (B) - Body ground Always 10 kohms or higher A17-2 (B) - Body ground Always 10 kohms or higher A17-3 (B) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
4. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - NO. 1 INTEGRATION RELAY) Disconnect the air conditioning amplifier assembly connector. Disconnect the engine room relay block and junction block (No. 1 integration relay) connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition H85-18 (PTC1) - 1G-17 (PTCA) Always Below 1 ohms H85-38 (PTC2) - 1G-26 (PTCB) Always Below 1 ohms H85-16 (PTC3) - 1G-25 (PTCC) Always Below 1 ohms H85-18 (PTC1) - Body ground Always 10 kohms or higher H85-38 (PTC2) - Body ground Always 10 kohms or higher H85-16 (PTC3) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
5. REPLACE NO. 1 INTEGRATION RELAY Replace the No. 1 integration relay. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/body-electrical/#power-distribution-service-information) . HINT: Since the No. 1 integration relay cannot be inspected while it is removed from the vehicle, replace the No. 1 integration relay with a new or a known good one and check that the condition returns to normal. Check if the same problem occurs again. OK Same problem does not occur. NG --> See step 6 OK --> END (NO. 1 INTEGRATION RELAY WAS DEFECTIVE)
6. PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to «PROBLEM SYMPTOMS TABLE»(ref-568603-S01769296392013072300000)
7. REPLACE PTC HEATER ASSEMBLY. Refer to «DISASSEMBLY»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)

When the combination switch assembly (ECO switch) is turned on, the air conditioning amplifier assembly receives an ECO switch ON signal and controls the air conditioning to enhance fuel efficiency.

When the heater is on, the engine ON request coolant temperature will be set to a lower level. Thus, the length of time that the engine operates to generate the heat necessary to operate the heater will be limited. When the engine coolant temperature drops, the amount of air flow of the blower motor will also decrease. If FOOT/DEF or DEF is selected, or if the temperature is set to MAX HOT, the fuel efficiency control due to the combination switch assembly (ECO switch) operation will be canceled.

When the air conditioning is used to cool the vehicle, the power consumption of the compressor will be limited. Initially, the air conditioning will operate normally until the cabin temperature stabilizes. After the cabin temperature stabilizes, the power consumption of the compressor will be limited while stabilizing the cabin temperature. If the temperature is set to MAX COOL, the fuel efficiency control due to the combination switch assembly (ECO switch) operation will be canceled.

Scheme 147

Scheme 148

1. READ VALUE USING TECHSTREAM Connect the Techstream to the DLC3. Turn the power switch on (IG). Turn the Techstream on. Enter the following menus: Body Electrical / Air Conditioner / Data Test. Check the values by referring to the table below. AIR CONDITIONER Tester Display Measurement Item/Range Control Range Diagnostic Note ECO Switch ECO switch / OFF or ON ECO switch not operated: OFF (when knob is not held in ECO position) - ECO switch operated: ON (when knob is held in ECO position) OK ECO switch condition displayed on the Techstream changes with the actual switch operation. NG --> See step 2 OK --> See step 4
2. INSPECT COMBINATION SWITCH ASSEMBLY (ECO SWITCH) Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition H72-5 (ECO) - H72-13 (E) ECO MODE switch off (when knob is not held in ECO position) 10 kohms or higher H72-5 (ECO) - H72-13 (E) ECO MODE switch on (when knob is held in ECO position) Below 1 ohms TEXT IN ILLUSTRATION *a Component without harness connected (Combination Switch Assembly (ECO Switch)) NG --> See step 5 OK: Go to next step
3. CHECK HARNESS AND CONNECTOR (COMBINATION SWITCH - AIR CONDITIONING AMPLIFIER) Disconnect the H72 combination switch assembly (ECO switch) connector. Disconnect the H85 air conditioning amplifier assembly connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition H85-15 (ECON) - H72-5 (ECO) Always Below 1 ohms H85-15 (ECON) - Body ground Always 10 kohms or higher H85-35 (SG-4) - H72-13 (E) Always Below 1 ohms H85-35 (SG-4) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> See step 6
4. PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to «PROBLEM SYMPTOMS TABLE»(ref-568603-S01769296392013072300000)
5. REPLACE COMBINATION SWITCH ASSEMBLY (ECO SWITCH). Refer to «REMOVAL»(ref-568590-S38400569132013072300000)
6. REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to «REMOVAL»(/lexus/ct/i-2010-2014/remont/automatic-hvac-system/#air-conditioning-system-service-information)

Power is supplied to the air conditioning amplifier assembly when the power switch is turned on (IG).

The power is used for operating the air conditioning amplifier assembly, servo motors, etc.

Scheme 149

The back-up power source circuit for the air conditioning amplifier assembly is shown below. Power is supplied even when the power switch is turned off. The power is used for DTC memory etc.

Scheme 150

See also:
• REMOVAL
• REMOVAL