Refrigerant leakage is the most common fault in air conditioning in summer. Refrigerants need to be added once a year, and some may be added once every 2 months. Refrigerant leakage is likely to cause environmental pollution and increase vehicle owners' maintenance costs and time. The following are the seven methods of automobile air conditioning leak detection. If there is oil stain somewhere, it may be a leak point. Visual leak detection is simple and easy to do, but there is no cost, but there are great defects, unless the system suddenly breaks large leaks, and the system leakage is liquid colored medium, otherwise the visual leak detection can not be located, because the place of leakage is very fine, and the automobile air tone itself has many parts almost invisible. 10-20kg/cm2 pressure nitrogen is added to the system and soap water is applied to all parts of the system. The bubble point is the leakage point. This method is the most common method of leak detection at the current roadside repair factory, but the human arm is limited, the range of human vision is limited, and many times can not see the leak at all. 10-20kg/cm2 pressure nitrogen is added to the system to immerse the system into water. The bubble point is the leakage point. This method is the same as the previous method of soapy water leak detection, although the cost is low, but it has obvious disadvantages: the moisture of the leak detection is easy to enter the system, causes the material in the system to be corroded, and the high pressure gas may cause more damage to the system. The cost of maintenance and maintenance is rising. Light the leak light, hold the air tube on the halogen lamp, and when the pipe is close to the system leakage, the color of the flame turns to purple and blue, which indicates that there is a lot of leakage. In this way, open flames are not only dangerous, but also harmful gas generated by the combination of open flames and refrigerants, and it is not easy to locate the leak spots accurately. So this method is almost useless now. If you can see it, it may be in the stage of uncivilized society. Using the pressure difference inside and outside the system, the pressure difference is amplified by the sensor, and the result of the leak detection is expressed in the way of digital or sound or electronic signal. This method can only know qualitatively whether the system is leaking and not accurately find the leak point.