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/-14 | 43.3 | 20/68 | 12.1 |
0/32 | 27.6 | 30/86 | 8.3 |
10/50 | 18 | 40/104 | 5.8 |
