Performed preventative maintenance for a American standard system model #Aud120r9v5k5, serial #9395ym41g. I powered the system down and removed the access panels to the system. I removed and cleaned carbon off of the flame sensor. Cleaned out the burners and burner box. Replaced the air filter size 20x25x1 supplied by the homeowner. Checked all electrical components to ensure that they are secure and in good condition. Tested the drain line and condensate pump with several bottles of water to ensure that there are no leaks or clogs. I powered up the system and called for heat. The inducer amp draw is at .85, the blower motor amp draw is at 8.4. I took a combustion analysis test and got the following readings 02 is at 11%, co is at 7ppm and the system is operating at 83% efficiency. I ended the call for heat and observed the system shut down normally. The system is operating properly at this time.