Performed heater tune-up on a Carrier gas furnace 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. As I was finishing the tune-up on the furnace I did notice the roof has a small water leak by the dryer vent penetration. No major issues were found. The system is operational at this time.