1.Working Principle Built-in negative temperature coefficient thermistor: Low coolant temperature → High resistance High coolant temperature → Low resistance ECU calculates temperature via voltage changes and adjusts fuel injection, ignition and cooling fan. 2. Standard Parameters R25: 2kΩ ~ 3kΩ common B value: 3950K / 3435K Working temp: -40℃ ~ 130℃ Accuracy: ±1~2℃ 3. Structure NTC thermistor chip (sealed) Brass threaded probe (contacts coolant directly) Rubber sealing ring (prevent coolant leakage) Plastic connector (2-pin most common) Mounting thread: M12, M14, 1/8NPT etc. 4. Installation Position Thermostat housing, cylinder head water channel, engine water outlet pipe. 5. Core Functions Cold start enrichment: More fuel for smooth cold startup Optimize fuel consumption after warming up Control radiator cooling fan switch Feed temperature data to dashboard water temp meter Assist transmission shift logic and EGR valve control 6. Typical Fault Symptoms Hard cold start, rough idle when cold Higher fuel consumption, black exhaust smoke Water temperature gauge shows abnormal reading Cooling fan always on or never activates Engine fault code stored, power limited 7. Application Gasoline & diesel passenger cars, trucks, motorcycles, construction machinery engines