Toyota 4Runner: Evaporator Temperature Sensor Circuit (B1413)

Toyota 4Runner Service Manual / Vehicle Interior / Heating / Air Conditioning / Air Conditioning System(for Manual Air Conditioning System) / Evaporator Temperature Sensor Circuit (B1413)

DESCRIPTION

The No. 1 cooler thermistor is installed on the evaporator in the air conditioning unit to detect the temperature of the cooled air that has passed through the evaporator and control the air conditioning. It sends appropriate signals to the No. 1 air conditioning amplifier assembly. The resistance of the No. 1 cooler thermistor changes in accordance with the temperature of the cooled air that has passed through the evaporator. As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

The No. 1 air conditioning amplifier assembly applies voltage (5 V) to the No. 1 cooler thermistor and reads voltage changes as the resistance of the No. 1 cooler thermistor changes. This sensor is used for frost prevention.

DTC Code	DTC Detection Condition	Trouble Area
B1413	An open or short in the No. 1 cooler thermistor circuit.	No. 1 cooler thermistor Air conditioning harness assembly No. 1 air conditioning amplifier assembly

WIRING DIAGRAM

PROCEDURE

1.	READ VALUE USING TECHSTREAM (NO. 1 COOLER THERMISTOR)

(a) Use the Data List to check if the No. 1 cooler thermistor is functioning properly (See page ).

Air Conditioner

Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
Evaporator Fin Thermistor	No. 1 cooler thermistor / Min.: -29.7°C (-21.46°F) Max.: 59.55°C (139.19°F)	Actual evaporator temperature displayed	Open in the circuit: -29.7°C (-21.46°F). Short in the circuit: 59.55°C (139.19°F).

Tester Display

Measurement Item/Range

Normal Condition

Diagnostic Note

Evaporator Fin Thermistor

No. 1 cooler thermistor /

Min.: -29.7°C (-21.46°F)

Max.: 59.55°C (139.19°F)

Actual evaporator temperature displayed

Open in the circuit: -29.7°C (-21.46°F).

Short in the circuit: 59.55°C (139.19°F).

OK:

The display is as specified in the normal condition column.

Result

Result	Proceed to
OK (When troubleshooting according to problem symptoms table)	A
OK (When troubleshooting according to the DTC)	B
NG	C

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

REPLACE NO. 1 AIR CONDITIONING AMPLIFIER ASSEMBLY

2.	INSPECT NO. 1 COOLER THERMISTOR

(a) Remove the No. 1 cooler thermistor (See page ).

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
1 - 2	-10°C (14°F)	7.30 to 9.10 kΩ
	-5°C (23°F)	5.65 to 6.95 kΩ
	0°C (32°F)	4.40 to 5.35 kΩ
	5°C (41°F)	3.40 to 4.15 kΩ
	10°C (50°F)	2.70 to 3.25 kΩ
	15°C (59°F)	2.14 to 2.58 kΩ
	20°C (68°F)	1.71 to 2.05 kΩ
	25°C (77°F)	1.38 to 1.64 kΩ
	30°C (86°F)	1.11 to 1.32 kΩ

Text in Illustration

*a	Sensing Portion
*b	Resistance
*c	Allowable Range
*d	Temperature

NOTICE:

Even slightly touching the sensor may change the resistance value. Be sure to hold the connector of the sensor.
When measuring, the sensor temperature must be the same as the ambient temperature.

HINT:

As the temperature increases, the resistance decreases (refer to the graph).

REPLACE NO. 1 COOLER THERMISTOR

3.	INSPECT NO. 1 AIR CONDITIONING AMPLIFIER ASSEMBLY

(a) Remove the No. 1 air conditioning amplifier assembly (See page ).

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
z15-6 (TE) - 2	Always	Below 1 Ω
z15-5 (SG-3) - 1	Always	Below 1 Ω
z15-6 (TE) - Body ground	Always	10 kΩ or higher
z15-5 (SG-3) - Body ground	Always	10 kΩ or higher

Text in Illustration

Front view of wire harness connector

(to No. 1 Cooler Thermistor)

Front view of wire harness connector

(to No. 1 Air Conditioning Amplifier Assembly)

REPLACE NO. 1 AIR CONDITIONING AMPLIFIER ASSEMBLY

REPLACE AIR CONDITIONING HARNESS ASSEMBLY

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