Performed preventative maintenance on a Lennox furnace.. upon arrival I watched the system cycle on with a call for heat. I checked and cleaned flame sensor of any carbon. I brushed out burner compartment. I checked operation of pressure switches. Replaced filter sized 16x25x1. I checked all electrical components to ensure the connections are good. Took amp readings on inducer and blower motor and both are in good range. Checked operation of condensate pump. Watched system cycle off when temperature was reached. Returned thermostat to the homeowners desired temperature. System is working properly at this time. Model # G60UH-48C-110-10 Serial # 5911G19305 Filter - 16x25x1