Customer states that the heat pump made a weird noise and had ice building up on the coil. Technician checked functions in heating and in cooling. Reversing valve, defrost control board, heat strips and outdoor thermostat are all in working order. Force tested defrost in front of the customer and he states that is the sould he heard. System functioning normally. There is no drain protection on the system. Highly suggest installing a drain switch to prevent possible water damage in case of a blockage in the primary drain.