Tested condensate pump multiple times and it drained correctly. I filled the Coil drain pan and it drained correctly. I ran the humidifier and noticed no leaks. I shortened the drain hose for the condensate pump so it was above the water in the water drain. I tested sub cooling and it was inside its passing parameters.I took the coil door off and checked and confirmed the drain pan was in the rails. I noticed the combustion air drain clamp was loose. Tightened it. The owner noticed the leak while cooling. I could not recreate the leak.