Performed preventative maintenance on a Lennox furnace model #g60uh-48c-110-07, serial #5908a02004. Upon arrival the system was calling for heat so I took a combustion analysis test and received the following results, o2 is 13.7% and the co levels are 5ppm. The inducer motor and blower motor amp draws are within normal range. I powered the system down and removed the access panels. Removed and cleaned carbon off of the flame sensor. Cleaned out the burners and burner box. Checked the pressure switch for clogs and tested the drain line and condensate pump with several bottles of water to ensure that there are no leaks or clogs in the system. Checked all electrical connections to ensure that they are secure and in good condition. Performed humidifier service for a healthy climate humidifier. Removed and replaced the old #35 water panel. Cleaned out the housing and drain. I powered the system back on and tested for proper operation. Both systems are operating properly at this time.