Performed single system heating maintenance. Filter is not too bad. Customer states that they are receiving them tomorrow and will change. Inspected electrical connections, and components of indoor air handler. Tested and inspected emergency heat strips. Used lemon scented sanitizer to clean surfaces and treat evaporator. Blew out the drain line and treated with sanitizer. Operated system to inspect zoning and refrigerant levels. Tested the defrost cycle. System is operating properly at this time.