Air conditioners do not use up refrigerant and refrigerants do not wear out. If you are low, you have a leak somewhere in your equipment. The problem is finding the leak. Sometimes the leak is obvious due to its size or location. Some leaks are very small and almost impossible to find. There are several ways to find leaks: soap bubbles, electronic leak detectors, halite torch, ultrasonic, and fluorescent dyes. It is up to the technician to decide which the best way to find the leak is. Generally an electronic leak detector is the best and easiest way to find a leak. Dyes should only be used as a last resort because you have to wait for a large enough leak to be detected by the florescent light.