Completed two system, furnace, maintenance and inspection. I tested components and amp draws. I tested temp splits and cleaned flame sensors. I wiped both units down. I changed out. Customer provided air filters. I changed out the water panel for the humidifier. The blower wheel on the main floor system is getting layers of dirt built on the fins. I showed customer the current condition and due to it being colder out. I recommended that we revisit the conversation of cleaning the blower wheel in the spring. Both furnaces are operating properly at departure.