Performed heater tune-up on a Carrier dual fuel system and a York 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 on both furnace systems. No major issues were found. All air purifiers are on and working. Both systems are operational at this time.