A customer reported that their AC was running constantly but the air from the vents felt cool, not cold, and the house could not get below 78 degrees. I connected refrigerant gauges and confirmed the system was critically low, indicating a leak. Using an electronic leak detector, I pinpointed the source at a solder joint on the indoor evaporator coil. I recovered the remaining refrigerant, repaired the leak, pressure-tested the system to ensure it was sealed, and then recharged it to the precise factory-specified level. The customer was happy that the root cause was found and fixed properly and called back an hour later to say the air from the vents was "ice cold."