Performed the heater tune-up on a Carrier gas system. Checked the electrical, mechanical and performance systems of the unit. Cleared, cleaned, flushed and treated the drain line and cleaned the exterior of the furnace. I replaced the high voltage wire nuts with a Wago wire connector. I also replaced the return air filter. I checked the static pressure of the system and found that the fan speed was set to deliver roughly 1800 cfm on a 5-ton system. This air flow is good for this size system, but the total static pressure reading is .83 which is high. No other major issues were found, and the system is operational at this time.