Furnace Tune-Up- Raised the ductwork starting at the furnace all the way to the end and properly securing the evaporator coil to the furnace. Taped and sealed the joints. Performed a heating preventative maintenance service on a gas furnace. Removed and cleaned the flame sensor. Blew out the drain line and trap. Checked the gas pressures, 16” wc incoming/ 9.6” wc at the manifold. Replaced the air filter, 14x24x1 Started and checked the safeties. Performed a combustion test. 9.0% o2, 19 ppm, 90.6% efficient. System is operating properly.