Performed heating maintenance on 4 year old Lennox unit. Checked filters and found them in good condition, Mr. Martian replaces his own filters. Temperature rise is within limits. Inspected blower compartment and found blower wheel to be clean and balanced. Inspected flame sensor and found it to be clean. Checked all electrical connections. Tested resistance of hot surface igniter. Measured external static pressure and found it to be near mfg’s recommendation. Flushed condensate drain with water. All electrical amp draws are within tolerances. Prior to departure I ensured the furnace was operating normally after my maintenance inspection.