Leak detection

Leak detection – seven methods to trace leaks

Leak detection is a hot topic in every A/C workshop – and not only for service on conventional R 134a A/C systems, but also for systems charged with alternative refrigerants, such as R 1234yf or CO2. There is an overview of the seven most commonly used methods to trace leaks, plus some recommendations from our experts.

1. UV leak detection

A special, fluorescent additive is injected into the refrigerant circuit – either via the A/C service unit or manually. Some new drier models are already fitted in the factory with such additives. When the A/C components are illuminated with a UV lamp and viewed through yellow UV protection goggles, the leak appears brightly lit up. Visibility is ensured even where oil-covered engines are concerned and even at some distance. Unlike the forming gas method, UV leak detection is also suitable for tracing ultra-fine leaks. Where vibration leaks are concerned it is the only method available.
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UV leak detection
2. Nitrogen

This method involves the production of positive pressure through nitrogen or negative pressure through vacuum by the A/C service unit. Leak detection through differential pressure is mainly suitable for the initial testing of strongly leaking or even empty systems. It only indicates that the system is leaking – not where the leak is. Testing is only possible with A/C service units that automatically stop when it is impossible to generate vacuum (e.g. all WAECO ASC service units). If the process continues without fault warning, you can be certain that the system has no leak and may be charged with refrigerant. The requirements of the Chemicals Climate Protection Ordinance are met.
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Nitrogen leak detection
3. Tracer or forming gas

Forming gas consists of 95 % nitrogen and 5 % hydrogen. The operating principle is similar to that of electronic leak detection. The difference is that the operator has to fill the system with test gas when the refrigerant has been removed. The drawback of this method is the length of time required (after 15 minutes the hydrogen has almost completely diffused and must be replaced). Another disadvantage is the fact that testing takes place when the system is not operating. “Vibration leaks” which occur while the engine is running can therefore not be detected. (The system needs refrigerant to operate, but it cannot be recharged yet because of the leak!) Moreover, leak detection with forming gas requires clean and constant ambient conditions (for example no draughts in the workshop).
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Forming gas leak detection
4. Electronic leak detection

Finding very small leaks is no problem for electronic leak detection systems. In some sections of the A/C system it is difficult though to apply the probe correctly, or at least very time-consuming.
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electronic leak detection
5. Vacuum check

Fully automatic with A/C service units from Dometic WAECO.
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Vacuum leak detection
6. Simple bubble test

Looking for a leak with lather, the so-called “bubble test”, belongs to the oldest methods of leak detection. It has become almost insignificant, however, as it is impossible to find very small leaks using this method.

7. Ultrasonic leak detection

Tracing a leak is easy and convenient with the Marksman Ultrasonic leak detector. Fitted with an Internal Noise Control system, this tool is unaffected by ambient noise, so it is also reliable in noisy surroundings. The degree of leakage is indicated by a 5-LED display and an additional warning tone.
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Ultrasonic leak detection

Leakage control – an absolute must

The utopia of a maintenance-free A/C system has been abandoned long ago. These days, A/C experts accept the fact that refrigerant losses occur with virtually every system. These losses do not always result from torn ducting or damages through accidents. Even totally intact systems lose some refrigerant – through the ducting and piping system, screw connections, sealing rings, etc. Such losses particularly affect modern systems containing far less refrigerant than former system generations.

The law forbids recharging defective A/C systems – after all, R 134a is regarded as an environmental hazard and climate killer. Regular leakage checks are in the interest of the vehicle owner to prevent compressor damage.

Decreasing refrigerant charging amounts in automotive A/C systems call for more sensitive leak detection equipment. This is where TRACER®, a quality brand, provides a convincing solution with its highly fluorescent additives and advanced LED blue light UV technology.
Left: highly fluorescent TRACER® sticks in the light of the LED blue light UV lamp – fast and reliable leak detection. With TRACER® products, the UV additive and lamp are perfectly coordinated. Right: low fluorescence no-name additive – potential leaks can only be detected with difficulty.


UV leak detection – always with the matching UV additive!

A PAG and PAO mixture do not form a consistent oil film. As PAG is heavier, it settles below the PAOs. A phase separation is clearly visible in static condition. During the start-up operation of the A/C system inconsistencies in the mixture can occur and cause damage to the compressor. Given the clear phase separation of the two oils, there can be no such thing as a universal UV additive. The UV-additive is contained in a carrier oil. If the different oils do not mix, the UV additive will not mix 100 % with the two oils either. The consequence is that it “sags through”. If the oil and the UV additive are a perfect match, the UV additive will form a stable and uniform blend with the compressor oil.

Conclusion: Always mix the right oil with the right UV additive. There are no universal solutions.


Professional standard

ASC by WAECO is, and has been for years, the abbreviation for excellent quality and cutting-edge technology in A/C service equipment. The series is constantly improved and complemented to meet future requirements. All ASC service units are state of the art and fully automatic

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