An aircon re-gas can detect major leaks by carrying out a vacuum check on the system and telling you how much, if any, gas was remaining. If the vacuum leak fails the machine will not allow us to put more gas into the system, at this point further investigation would be required to detect the leak location and carry out the appropriate repair. The machine also put a Ultra Violet Dye into the system which allows us to locate any leaks should one be present.