Removed, cleaned and installed gas burners Removed, cleaned and installed flame sensor Inspected heat exchanger Tested igniter Checked condensate trap Checked blower motor Checked and tested ventor motor Checked filter Adjusted gas outlet pressure to OEM spec Recommend Replace flame sensor -Flame sensor is rusty and may not read flame. Resulting in ignition failure Inducer motor- inducer is using more power than designed for. Burners- all three burners are rusted in spots that show signed of pending failure. Ex air -169 , co in home 4ppm, showed customer cracked heat exchanger Dan Fox second opinion Tech has turned off system as it is unsafe to run Now scheduling spring AC tune ups