Completed 2 system furnace repair and preventative maintenance check. Comfort Club Membership renewal. Replaced the filter. Checked the electrical and safety switches. All are okay at this time. Found a worn ignition and a weak flame safety sensor. Will replace both parts during the next appointment in the fall. Found the system production over 100ppm for carbon monoxide. Performed a combustion calibration and replaced the UV bulb. Tested and the system is heating normally at this time.