2020 Trane AC running in great condition. 20x25x4 air filter is new today. Whistling noise was due to air filter door not being closed all of the way and allowing some air to pass through. Visual inspection of indoor coil. Flush drain pan and drain lines. Run test unit in cooling mode from thermostat. Delta t of 20F with supply temp of 44F. Refrigerant pressures are within spec. High 240psi with 11F SC, low 110psi with 8F SH. Outdoor coils are in clean condition. Outdoor fan motor and compressor are operating within specs. System is operating properly, efficiently and ready for Summer.