Completed 3 system furnace repair and preventative maintenance check. Found the upstairs and main level to be running with no issues. They are 4 years old and still clean. There is no wearing of the components. The basement level is pushing 12 years old and shows signs of a possible leak and corrosion around the coil. The blower wheel is dirty and the capacitor is rusted. Recommended having a consultant come out and give an estimate on replacing the system.