1.Working Principle Equipped with negative temperature coefficient NTC thermistor: Temperature rises → resistance drops; Temperature falls → resistance rises. The ECU converts resistance value into refrigerant temperature data to execute anti-freeze, compressor protection and cooling logic. 2. Common Electrical Specifications R25: 10kΩ / 5kΩ mainstream B value: 3435K, 3950K Temperature accuracy: ±1℃ Operating temperature range: -40℃ ~ 125℃ Fast heat-conducting copper tube shell for rapid temperature response 3. Internal Structure Epoxy/glass sealed NTC thermistor core Thin copper tube sensing head Spring fixing clip for tight fitting on AC copper pipes Heat-resistant automotive wiring harness wire Vehicle-specific plastic plug (custom terminals) 4. Core Functions Evaporator anti-freeze protection Prevent the evaporator from icing up due to ultra-low refrigerant temperature, which would block air flow and damage the compressor. Compressor cycle control Adjust compressor clutch on/off according to pipe temperature to keep stable cooling effect. Refrigerant leakage auxiliary judgment Abnormal low pipe temperature without cooling indicates insufficient refrigerant. Overheat protection Detect overhigh temperature of high-pressure refrigerant pipeline to cut off compressor power for safety. 5. Typical Fault Performance Car air conditioner blows weak cold air, evaporator freezes heavily Compressor frequently engages and disengages On-board computer reports AC temperature fault code Cooling effect unstable, sometimes cold sometimes warm 6. Application Range Passenger cars, SUVs, pickup trucks, vans, engineering vehicle air conditioning systems