Performed customer 1 system fall (heat) homecare maintenance check Gas furnace is 15 years old, ac and coil is 15 years old Changed (20x25x4) media filter Did full evaluation of system. Blower wheel is very dirty, inside furnace is dirty due to dirt and rodent droppings and no top of the furnace is very dirty due to same issue. The secondary heat exchanger behind the blower compartment in very dirty and will lead to furnace overheating activating the high limit switch. Inducer draft motor is failing, windings are very loud on start up and shut down. Cleaned flame sensor and pressure switch tube port. Burners are very rusted. Heat exchange is compromised. Heat exchanger is in bad shape there is a lot of rusting on tubes, and inside the heat exchanger tubing. When system lights unit is having a rollout due to poor heat exchanger. Advised customer of issues with furnace. The duct work is not insulated all the way to the boots causing unit to sweat and will start damaging customers floors.