Air Conditioning System Leak Testing. The customer complains of poor or no air conditioning cooling. After further diagnosis, the system is found to be low or empty of a refrigerant charge, but when using an electronic leak detector, no leak can be found. CAUSE: In most cases, an electronic leak detector is not sufficient for identifying small leaks in the system. Electronic leak detectors can give false alarms and can lead to an improper diagnosis of small leaks. A leak cannot be located exactly if accessibility is impaired (in the case of the expansion valve, evaporator or condenser).