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Automotive air conditioning leak detection tips and parts of three methods to determine leakage

The weather gradually turns hot, automotive air conditioning repair quickly into the season, all kinds of maintenance on the amount of air-conditioning system failure is also gradually increased. Common faults in air-conditioning system, the leak inspection and maintenance of the most failed first-line maintenance technicians to make a headache. Check air-conditioning system due to leakage points and time-consuming effort, if there is no good way, not only will greatly affect the efficiency of maintenance work, it will lead to customer satisfaction greatly reduced.

In their daily work which the author found that the vast majority of front-line technicians, carrying out air leak investigation, he will use a fluoride table (assembly of high and low pressure two headers) (Figure 1) to test: Using high-pressure pipe access system, low pressure it can not control access system, or that have access to high-low pressure pipe systems but less pressure method. The use of nitrogen pressure, the holding pressure is generally about 1 h or more, said system does not leak. But sometimes the phenomenon occurs off the table (because the air-conditioning system piping within the expansion valve, compressor and other large volume parts, the pointer will be a sharp decline in the value of direct pressure), and the generation of slow channeling gas, this phenomenon is false leak out in Table time will not longer happening again. Disadvantage of this approach is not sufficiently precise, time-consuming, the customer is often a result of waiting too long to complain. To address this issue, the author sums up their air-conditioning leak of some of the tips in this recommendation to you, hoping to help you solve this problem.

1. Normal pressure nitrogen gas leak detection method improved

   In the leak before the first fluoro-table modification this: remove the low-pressure header, and then a header instead of low-voltage high-pressure header. Such a fluorine on the table is equipped with two high-voltage header (Figure 2). Modified because, according to the method previously used low-voltage table pressurized leak detection, often will produce low-voltage table is damaged, (currently most of the pressure detection method recommended inflation pressure of 0.78 MPa or so, just the largest range range of low tables. ) I will change into two high-pressure pressure gauge header, not only can increase the pressure leak detection efficiency and convenience, but does not produce fluorine damage to the table.
 Leak detection, respectively, the two header access to high and low pressure pipe joints, using nitrogen pressure (Figure 3). Pressure should be increased to between 2.0 ~ 2.5 MPa (Figure 4), because the air-conditioning fan in general high-speed rotation when the pressure generated between 1.7 ~ 2.0 MPa, which means air-conditioning time to time in this state to work under pressure, leakage will also be occurs at this time. Most car air-conditioning system design pressure range is generally not less than 3.0 MPa, that is, in this pressure range will not damage the system, but the actual maintenance of the system, we should also consider the problem of aging, the author summed up in practice this relatively safe and fast and practical range of nitrogen pressure.

In this pressure (2.0 ~ 2.5 MPa), if the air-conditioning system to retain pressure 20 min (can not have off the table phenomenon, pointer instructions should be the slightest change), the basic system can be determined to be leak-free (but should be noted that the compressor is a functioning components). Because at this time the pressure of high pressure and low pressure two consistent on both sides of the instructions should be the same and unchanged. However, this leak detection method of operation for the compressor pump head occurs at the work of the leakage is not applicable (this failure not serious, the static pressure leak is powerless). And the general fluorine leak wears table compared to the greatest advantage of this approach is that fluoride does not damage the table (low table), measuring accurate and fast.

 With the continuous development of science and technology, many of automotive air conditioning testing and maintenance of advanced equipment is already available, today a lot of automotive air conditioning refrigerant recycling equipment filling with air-conditioning system leak detection. However, for various reasons, this type of equipment in a variety of comprehensive maintenance of the enterprise is not yet universal. In these the lack of professional equipment, the maintenance of the enterprise, these leak detection methods may be able to alleviate the short time, but he knew that was to be more professional, standardized testing equipment replaced.

 2. Determine the leak location method

    (1) pressurized bubble leak detection method: using nitrogen pressure leak was detected at the same time, the use of detergent behind the aqueous foam coated air-conditioning system pipelines, as well as exterior components (recommended by sponge painting, so that maximum bubble volume), to see if there are air bubbles produced. Recommend the use of detergent behind the reason is that its fine bubbles and keep a long time, much better than soap and other foam solutions. Use, can be coated compressor pump head office covered by the system pressure of 2.0 ~ 2.5 MPa, the up and down shaking and shaking as much as possible to increase the frequency of pump head office can check whether the leak. I have found too much from such a leak method has been applied. Such leak detection method is simple and low cost, suitable for routine air-conditioning system leak checks.

 (2) fluorescent tracer leak detection method (Figure 5): the use of fluorescent light exposure in the leak will be issued under the principle of fluorescent yellow-green, fluorescent agents will be joined by a certain percentage of air-conditioning system, the system works, after 2 h to wear special glasses, with the leak detection light radiation system, the outside of the spill will show a bright yellow fluorescence. This leak costly, but very professional and accurate, extremely small amount of leakage can be found, and now “4S” shops generally use this approach.

  However, the fluorescent leak detection method, there are still some drawbacks: fluorescence fluorescent leak detection must be poured into the pending inspection agents charge of refrigerant in the system, and co-soluble in order to run for at least 2 h after irradiation using a dedicated light detectors of their drain-source and leakage, if it is a slow leak recommendations to the owner to use a period of time, in the lack of air conditioning refrigerant re-emergence phenomenon Depot detect leakage, if found to leak point dismantling air-conditioning system components must be broken down, then added to the original leak testing system The fluorescent agent and refrigerant have to be wasted part of the lead material waste. In addition, using fluorescence leak detection, the system difficult to achieve a true cyclic pressure conditions (high temperature and pressure) running under pressure. According to the author of maintenance experience, and sometimes only at a higher leakage of the system under pressure to appear, so in leak detection, they tend to miss these obvious leakage points.

  (3) Electronic Leak Leak (Figure 6): use of specialized equipment probe in all possible leakage around the site of movement (speed not too fast), when the leak alarm device, that is that here there is leakage. Refrigerant evaporation due to fast, this method results in better use of small space, such as the evaporator and other parts. Air-conditioning fan suggested the use of low gear speed. But the instrument probe will be affected by moisture, oil and other unfavorable factors, and sometimes produce false positives, so pay attention to tips.

These three kinds of methods as long as the cross, flexible and timely application, I believe that air-conditioning system leak detection work will be a time-consuming effort to change the characteristics of the past, become easy, so as to first-line maintenance staff to bring a lot of convenience.