Performed precision AC tune up. Checked operating refrigerant pressures to ensure peak performance and efficiency. Tested power distribution system and corresponding starting components. Verified proper amp draw; optimal. Checked temperature differential across indoor coil. Washed outdoor coils thoroughly to maintain heat rejection. Purged drain line to clear lines. Used alkaline treatment to reduce bacterial growth within lines. Tested zoning control and zoning motor response. System operating within desirable specifications. All checks are good at this time. Replaced media filter 20x25