Cooling Box Sensor Circuit

HEATING / AIR CONDITIONING: AIR CONDITIONING SYSTEM: Cooling Box Sensor Circuit
- Cooling Box Sensor Circuit

DESCRIPTION

The No. 3 cooler thermistor is installed on the evaporator in the cooling box unit to detect the cooled air temperature that has passed through the evaporator and control the cooling box. It sends appropriate signals to the air conditioning amplifier assembly (for cool box). The resistance of the No. 3 cooler thermistor 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 (for cool box) applies voltage (12 V) to the No. 3 cooler thermistor and reads voltage changes as the resistance of the No. 3 cooler thermistor changes.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. INSPECT FUSE (A/C IG, ECU-B1)

(a) Remove the A/C IG fuse from the cowl side junction block LH.

(b) Remove the ECU-B1 fuse from the engine room relay block.

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

Standard Resistance:





NG -- REPLACE FUSE
OK -- Continue to next step.

2. CHECK HARNESS AND CONNECTOR (NO. 1 COOLER WIRING HARNESS - BATTERY)

(a) Disconnect the No. 1 cooler wiring harness sub-assembly connector.





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

Standard Voltage:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

3. CHECK HARNESS AND CONNECTOR (NO. 1 COOLER WIRING HARNESS - BODY GROUND)

(a) Disconnect the No. 1 cooler wiring harness sub-assembly connector.





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

Standard Resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

4. CHECK NO. 1 COOLER WIRING HARNESS SUB-ASSEMBLY (OPERATION)

(a) Replace the No. 1 cooler wiring harness sub-assembly with a normal one and check that the condition returns to normal.

OK:

Same problem does not occur.

NG -- CHECK NO. 3 COOLER THERMISTOR

OK -- REPLACE NO. 1 COOLER WIRING HARNESS SUB-ASSEMBLY

5. CHECK NO. 3 COOLER THERMISTOR

(a) Remove the No. 3 cooler thermistor Disassembly.





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

Standard Resistance:





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 (See the graph).

NG -- REPLACE NO. 3 COOLER THERMISTOR Disassembly

OK -- REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY (for Cool Box) Disassembly