AIR CONDITIONING SYSTEM(for Automatic Air Conditioning System) 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.

PROCEDURE

1. Click here

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

   
   

   1. Remove the A/C IG fuse from the cowl side junction block LH.

   2. Remove the ECU-B1 fuse from the engine room relay block.

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

      Standard Resistance
      Tester Connection Condition Specified Condition A/C IG fuse Always Below 1 Ω ECU-B1 fuse Always Below 1 Ω

   
   
   • OKClick here
   • NG

     REPLACE FUSE

2. Click here

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

   
   
   1. 

      Table 1.

      *1	Front view of wire harness connector: (to No. 1 Cooler Wiring Harness Sub-assembly)

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

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

      Standard Voltage
      Tester Connection Condition Specified Condition 4 (+B) - Body ground Always 11 to 14 V 1 (B) - Body ground Engine switch off Below 1 V Engine switch on (IG) 11 to 14 V

   
   
   • OKClick here
   • NG

     REPAIR OR REPLACE HARNESS OR CONNECTOR

3. Click here

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

   
   
   1. 

      Table 2.

      *1	Front view of wire harness connector: (to No. 1 Cooler Wiring Harness Sub-assembly)

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

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

      Standard Resistance
      Tester Connection Condition Specified Condition 6 (L) - Body ground Always Below 1 Ω

   
   
   • OKClick here
   • NG

     REPAIR OR REPLACE HARNESS OR CONNECTOR

4. Click here

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

   
   

   1. 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.

   
   
   • OK

     REPLACE NO. 1 COOLER WIRING HARNESS SUB-ASSEMBLY

   • NGClick here
5. Click here

   CHECK NO. 3 COOLER THERMISTOR

   
   
   1. 

      Remove the No. 3 cooler thermistor (Click here).

   2. 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

      Note:
      

      • 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.

      Tip:

      As the temperature increases, the resistance decreases (see the graph).

   
   
   • OK

     REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY (for Cool Box) (Click here)

   • NG

     REPLACE NO. 3 COOLER THERMISTOR (Click here)