Performed preventative maintenance on a Coleman furnace in basement. Upon arrival I watched system cycle on with call for heat. I performed a combustion analysis test and the results were: O2 14.2% and CO 4 ppm. I checked and cleaned carbon off flame sensor and cleaned burner section. Replaced uv bulb in system. I took amp draws from inducer motor and blower motor both were in good range. PAK is to be changed in spring. Watched system cycle off when temperature was met. System is working properly at this time. I performed a preventative maintenance on a Lennox furnace in the attic. Upon arrival I watched system cycle on with a call for heat. I performed a combustion analysis test and got the following results: O2 is 9.6% and CO is 20ppm. I checked all electrical components to ensure connections are good. Took amp draws on inducer fan and blower motor and both are in good range. I cleaned flame sensor and burner box. Watched system cycle off when temperature was met. System is working