Perfomed first furnace and ac check on system. System at one point was converted from electric to gas. Installer left old system and installed system 2 ft away. Created huge bypass for airflow. Informed customer that is a issue and both units won’t run properly until bypass is removed. Also informed customer temperature reading won’t be accurate or will I be able to tell how systems are actually running. Found humidifier doesn’t have feed tube and needs new pad. informed he will need a new humidifier. Cleaned both units, found voltage absorption system in furnace is outside manufacture specifications. Also found flue pipe set in boot. No tightening mechanism sealed with thumb gum. Informed customer of health concern. Informed customer possibly a design flaw could be install flaw. Customer hoping furnace and/or ac will fail sooner rather then later due to having home warranty and expecting replacement soon.0ppm co in supply. 9ppm co in flu. Within manufacture specifications as far as I