The Evaporator sensor located on the HVAC unit and detects the evaporator core temperature. It is a negative type thermistor whose resistance is inversely proportional to temperature. The Evaporator sensor converts the measured temperature into a 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.
DTC B1242 sets if Evaporator sensor signal is at or over 4.9V for 0.3 seconds.
Item | Detecting Condition | Possible Cause |
DTC Strategy |
•
Voltage check | 1. Open in signal circuit 2. Short to battery in signal circuit 3. Faulty Evaporator sensor 4. Faulty Air conditioner control Unit |
Enable Conditions |
•
Ignition ON | |
Threshold value |
•
Evaporator sensor signal is at or over 4.9V for 0.3 seconds. | |
Failsafe |
•
Control with the value of -2℃(28.4℉) |
※ 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 |
