The Evaporator sensor located on heater unit detects the core temperature. It is a negative type thermistor whose resistance is inversely proportional to temperature. Evaporator sensor transforms measured temperature into voltage value and delivers it to A/C ECU. when core temperature is blow threshold value, A/C ECU interrupts compressor relay power, in order to prevent evaporator freezing by excessive cooling.
The ECM sets DTC B1241 if there is a short circuit in evaporator sensor signal harness or the measured voltage value of the sensor is less than the threshold value(0.1V)
Item | Detecting Condition | Possible Cause |
DTC Strategy | ● Voltage check | ● Short circuit in harness ● Faulty Evaporator sensor ● Faulty A/C Control Unit |
Threshold value | ●< 0.1V | |
Detecting time | ● 0.3sec | |
FAIL SAFE | ● Control with the value of -2℃ |
※ Resistance value of evaporator sensor as a function of temperature.
Temperature(℃) | Resistance(㏀) | Temperature(℃) | Resistance(㏀) |
-10 | 13.56 | 20 | 3.06 |
0 | 8 | 30 | 1.97 |
10 | 4.87 | 40 | 1.31 |
