AIR CONDITIONING SYSTEM(for Automatic Air Conditioning System), Diagnostic DTC:B1412/12

DESCRIPTION

The cooler thermistor (ambient temperature sensor) is installed in the front part of the cooler condenser assembly to detect the ambient temperature and control the air conditioning auto mode. The sensor connected to the air conditioning amplifier assembly detects fluctuations in the ambient temperature. This data is used for controlling the room temperature. The sensor sends a signal to the air conditioning amplifier assembly. The resistance of the cooler thermistor (ambient temperature sensor) changes in accordance with the cooler thermistor temperature (ambient temperature). As the temperature decreases, the resistance increases. As the temperature increases, the resistance decreases.

The air conditioning amplifier assembly applies a voltage (5 V) to the cooler thermistor (ambient temperature sensor) and reads voltage changes as changes in the resistance of the cooler thermistor (ambient temperature sensor).

WIRING DIAGRAM

*a	Cooler Thermistor (Ambient Temperature Sensor)
*b	Air Conditioning Amplifier Assembly

PROCEDURE

1. READ VALUE USING INTELLIGENT TESTER (AMBIENT TEMPERATURE SENSOR)

   
   

   1. Use the Data List to check if the cooler thermistor (ambient temperature sensor) is functioning properly Click here.

      Air Conditioner

      Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
      Ambient Temp Sensor	Cooler thermistor (ambient temperature sensor) / Min: -23.3°C (-9.94°F) Max: 65.95°C (150.71°F)	Actual ambient temperature displayed	Open in the circuit: -23.3°C (-9.94°F). Short in the circuit: 65.95°C (150.71°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

   
   

   A

   PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Click here

   B

   REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY Click here

   C

2. INSPECT COOLER THERMISTOR (AMBIENT TEMPERATURE SENSOR)

   
   

   1. Remove the cooler thermistor (ambient temperature sensor) 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 (50°F) 3.00 to 3.73 kΩ 15°C (59°F) 2.45 to 2.88 kΩ 20°C (68°F) 1.95 to 2.30 kΩ 25°C (77°F) 1.60 to 1.80 kΩ 30°C (86°F) 1.28 to 1.47 kΩ 35°C (95°F) 1.00 to 1.22 kΩ 40°C (104°F) 0.80 to 1.00 kΩ 45°C (113°F) 0.65 to 0.85 kΩ 50°C (122°F) 0.50 to 0.70 kΩ 55°C (131°F) 0.44 to 0.60 kΩ 60°C (140°F) 0.36 to 0.50 kΩ

      Text in Illustration

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

      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.

      Tech Tips

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

   
   

   NG

   REPLACE COOLER THERMISTOR (AMBIENT TEMPERATURE SENSOR) Click here

   OK

3. CHECK HARNESS AND CONNECTOR (AMBIENT TEMPERATURE SENSOR - AIR CONDITIONING AMPLIFIER)

   
   

   1. Disconnect the A1 sensor connector.

   2. Disconnect the G25 amplifier connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition A1-1 - G25-5 (TAM) Always Below 1 Ω A1-2 - G25-13 (SG-2) G25-5 (TAM) - Body ground Always 10 kΩ or higher G25-13 (SG-2) - Body ground

   
   

   OK

   REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY Click here

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR