Performed heater tune-up on a Carrier furnace system. Checked the electrical, mechanical and performance systems of the unit. Cleared, cleaned, flushed and treated the drain line. Cleaned the exterior of the air handler and secured outdoor compressor wiring. I did find the fan setting on the thermostat was set to “circulate”. I recommended leaving the setting on “auto” to prevent excess humidity in the home during summertime. No other issues were found. The system is running at completion of service.