Lexus NX: Evaporator Temperature Circuit or Evaporator Fin Thermistor (B1413)

Lexus NX Service Manual / Vehicle Interior / Heating / Air Conditioning / Air Conditioning System / 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

  • No. 1 cooler thermistor (evaporator temperature sensor)
  • Air conditioning harness assembly
  • Air conditioning amplifier assembly

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

-

Body Electrical > Air Conditioner > Data List

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

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

B

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY

C

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)

OK

3.

CHECK AIR CONDITIONING HARNESS ASSEMBLY

(a) Disconnect the air conditioning harness assembly connector.

*1

Air Conditioning Harness Assembly

*a

Front view of air conditioning harness assembly

(to Air Conditioning Amplifier Assembly)

*b

Front view of air conditioning harness assembly

(to No. 1 cooler thermistor [evaporator temperature sensor])

(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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