Lexus NX: Evaporator Temperature Circuit or Evaporator Fin Thermistor (B1413)
DESCRIPTION
The No. 1 cooler thermistor (evaporator temperature sensor) is installed on the evaporator in the air conditioner unit to detect the temperature of the air that has passed through the evaporator and is used to control the air conditioning. It sends signals to the air conditioning amplifier assembly. The resistance of the No. 1 cooler thermistor (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 No. 1 cooler thermistor (evaporator temperature sensor) and reads voltage changes as the resistance of the No. 1 cooler thermistor (evaporator temperature sensor) changes. This sensor is used for frost prevention.
| DTC No. | Detection Item | DTC Detection Condition | Trouble Area | Memory | Note |
|---|---|---|---|---|---|
| B1413 | Evaporator Temperature Circuit or Evaporator Fin Thermistor | Open or short in No. 1 cooler thermistor (evaporator temperature sensor) circuit |
| Memorized (4 seconds or more) | - |
HINT:
The air conditioning amplifier assembly stores the DTC of the respective malfunction if it has occurred for the period of time indicated in the brackets.
WIRING DIAGRAM
CAUTION / NOTICE / HINT
NOTICE:
When the auxiliary battery is disconnected or the air conditioning amplifier assembly is replaced, be sure to perform servo motor initialization.
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PROCEDURE
| 1. | READ VALUE USING TECHSTREAM |
(a) Connect the Techstream to the DLC3.
(b) Turn the power switch on (IG).
(c) Turn the Techstream on.
(d) Enter the following menus: Body Electrical / Air Conditioner / Data List.
(e) Check the value(s) by referring to the table below.
Body Electrical > Air Conditioner > Data List| Tester Display | Measurement Item | Range | Normal Condition | Diagnostic Note |
|---|---|---|---|---|
| Evaporator Fin Thermistor | No. 1 cooler thermistor (evaporator temperature sensor) | Min.: -29.70°C (-21.46°F) Max.: 59.55°C (139.19°F) | Actual evaporator temperature displayed | - |
| Tester Display |
|---|
| Evaporator Fin Thermistor |
OK:
The display is as specified in the normal condition column.
| Result | Proceed to |
|---|---|
| OK (When troubleshooting according to Problem Symptoms Table) | A |
| OK (When troubleshooting according to the DTC) | B |
| NG | C |
| A | .gif) | PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE |
| B | | REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY |
|
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| 2. | INSPECT NO. 1 COOLER THERMISTOR (EVAPORATOR TEMPERATURE SENSOR) |
(a) Remove the No. 1 cooler thermistor (evaporator temperature sensor).
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(b) Inspect the No. 1 cooler thermistor (evaporator temperature sensor).
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| NG | | REPLACE NO. 1 COOLER THERMISTOR (EVAPORATOR TEMPERATURE SENSOR) |
|
| 3. | CHECK AIR CONDITIONING HARNESS ASSEMBLY |
| (a) Disconnect the air conditioning harness assembly connector. |
|
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| z2-6 (TEA) - aa1-1 | Always | Below 1 Ω |
| z2-5 (SGA) - aa1-2 | Always | Below 1 Ω |
| z2-6 (TEA) or aa1-1 - Body ground | Always | 10 kΩ or higher |
| z2-5 (SGA) or aa1-2 - Body ground | Always | 10 kΩ or higher |
| OK | | REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY |
| NG | | REPLACE AIR CONDITIONING HARNESS ASSEMBLY |
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