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 zoning operations and damper motor response. Checked primary drain to ensure no obstructions. Used alkaline treatment to reduce bacterial growth within lines. Replaced existing media filter 20x25. Checked temperature differential across indoor coil within target range. Air Purification system was currently due for UV replacement cartridge to restore Air Purifier to working order. Replaced UV bulb accordingly with customer approval with 36 month rating on replacement. Otherwise all checks are good at this time. System is currently operating within desirable specifications. Applied $25 referral discount to invoice balance.