Function and Application of Air Conditioner Evaporator Temperature Sensor

The problem of the air conditioner evaporator temperature sensor, this time focusing on the small components of the air conditioning system, may actually encounter abnormal cooling.

The air conditioner evaporator temperature sensor involves principles, fault manifestations, maintenance cases, enz. It is necessary to focus on integrating this information: the core function of the evaporator temperature sensor is to prevent frost protection (turn off the compressor when it is close to 0℃) and maintain refrigeration stability. The installation location is usually on the surface of the evaporator fins or nearby pipes. Failures can cause the air conditioner to “exhaust cooling” – hot and cold, or even ice on the evaporator blocking the air outlet.

Pay special attention to several technical details: most sensors are NTC thermistors (high resistance is about 10kΩ at low temperatures), and resistance drift may occur after failure (such as resistance increases, causing the compressor to stop prematurely). The repair cost varies greatly. The replacement assembly of a 4S shop may cost thousands of yuan, while the self-purchased sensor is only a few dozen yuan.

Users may be more concerned about fault judgment and solutions. It is necessary to highlight typical fault characteristics: Bijvoorbeeld, the air volume drops sharply after 10 minutes of refrigeration (a sign of evaporator icing), or a biting cold wind appears when the temperature is set to 26℃ (temperature control failure). The solution should distinguish between professional repairs and DIY processing, with particular emphasis on safe operation – some models require the dashboard to be disassembled, and non-professionals can easily damage the air duct.

The following is a system analysis of the air conditioner evaporator temperature sensor, integrating core functions, fault characteristics and maintenance solutions:
I. Core functions and technical principles

‌‌Anti-frost control‌
Real-time monitoring of the evaporator surface temperature (working range ‌-30℃~120℃‌), when the temperature is close to ‌0℃‌, the compressor circuit is immediately cut off to prevent the evaporator from freezing and blocking the air duct; the compressor is automatically restarted after the temperature rises to ‌3-4℃‌ to ensure the continuity of refrigeration.

‌Energy efficiency optimization‌
By dynamically adjusting the compressor start-stop cycle, idling energy consumption is reduced, and the refrigeration efficiency can be increased by ‌25-30%‌ during normal operation.
‌Sensor technology‌
The mainstream adopts ‌NTC thermistor‌ (resistance is about ‌10kΩ‌ at 20℃). The lower the temperature, the higher the resistance. The signal is transmitted to the air conditioning control unit (ACU) to achieve closed-loop control.

Air Conditioner Evaporator Temperature Sensor

Car air conditioner evaporator temperature thermistor switch sensor 97143-C5000

6445XL air conditioning evaporator temperature sensor suitable for Peugeot 508, Renault N100468

II. Fault symptoms and failure consequences
Geval: Due to sensor failure, the evaporator of Hongguang S model was frozen and dripping during high-speed driving. The cost of replacing the sensor was only 20 yuan (original parts), avoiding the cost of replacing the assembly.

III. Installation location and maintenance points
‌Hidden location‌
Located on the surface of the evaporator fin inside the center console (see the schematic diagram). The glove box and cover need to be removed to access. Some models need to remove the elastic buckle.
Installation diagram
‌Detection method‌
‌Resistance test‌: Standard resistance at 25℃ ‌5-15kΩ‌ (measured deviation>20% requires replacement).
‌Voltage diagnosis‌: Disconnect the plug to measure the ACU terminal voltage (usually 5V), and check the circuit short circuit if abnormal.

Iv. Maintenance plan and technological evolution
‌Low-cost replacement‌
DIY replacement: Online purchase of the adapter model (such as Peugeot 307 requires ‌CTS-08‌ model), the whole process takes about 30 notulen.
4S shop maintenance: including labor costs of about $200.
‌New generation technology‌
‌Bimetallic sensor‌: Direct mechanical temperature control using the difference in metal expansion coefficients, strong anti-electromagnetic interference.
‌Redundant design‌: High-end models add auxiliary sensors, and automatically switch to backup signals when the main sensor fails.

V. Preventive maintenance recommendations
‌Regular cleaning‌: Clean the evaporator fins every 2 years to prevent dirt from wrapping the sensor and causing temperature measurement delays.
‌Filter replacement‌: Air conditioning filter blockage will increase the risk of evaporator frosting, and it is recommended to replace it every 10,000 kilometers.

‌Industry trend‌: In 2025, the new photoelectric sensor will enter the testing phase, and the response speed will be increased to 0.1 seconden (5 times faster than NTC).