There are different methods to detect refrigerant leaks.
UV liquid is injected to the A/C system, then leak source is searched with UV lamp and special glasses. A bright reflection can be seen on the leak spot. The amount of UV liquid to be injected depends on the oil in the system. UV leak detection is the most popular detection method. Some car manufacturers inject UV liquid in the production line to assist customers.
Gas Leak Detector is another method which gives audio warning when gas is detected. Since sensor in the detector is sensible to other substances, it should be used carefully.
Recently, “spectrometers” are being used which are very sensitive and sensible only to the gas in question. These devices can even detect the leakage rate, however they are extremely costly.
Helium gas can also be injected to the A/C system and leak can be detected via helium detector. Since helium detectors are only sensitive to helium, leak detection is fast and accurate, however it is costly.
What is an air purge system?
In time, air sucked in from the leaks or hoses accumulates in the storage tank, which needs to be purged. In “semi-automatic” machines, purge must be done manually by the user. Storage tank pressure and temperature must be monitored closely to determine when air needs to be purged. Full automatic machines detect air in the system via electronic pressure and temperature sensors and purge it automatically.
How to determine the amount of refrigerant in car A/C system?
Refrigerant is recovered and weighed via electronic scale. The amount of refrigerant can be monitored continuously during recovery. Weighing is the only valid method.
What is a vacuum leak test?
Even though this is not a reliable leak detection method, it is easy to apply and must definitely be performed. The only problem is the moisture in the system which reduces current vacuum level and might create a false positive. If the system is vacuumed sufficiently, moisture will dry which will reduce the chance of getting a false positive. It should be kept in mind that no test has 100% success rate. Vacuum leak test is useful for checking the system after repairs. Vacuum gauge should be accurate and sensitive enough since it is monitored throughout this test.