Performed heater tune-up on two Carrier straight cool systems. Checked the electrical, mechanical and performance systems of the units. Replaced the return air filters. Cleared, cleaned, flushed and treated the drain lines. Cleaned the exterior of the furnace systems and washed both outdoor coils. I replaced the high voltage wire nuts with a Wago wire connector on both furnace systems. I also adjusted the airflow on the upstairs 3-ton system to deliver 1100 cfm. No other issues were found. Both systems are operational at this time.