Heating repair in hoschton. Homeowner stated system would run for 20 minutes then only blow cold air. Tested system and discovered weak flame safety and worn ignition. Dirty blower wheel and organic growth. Duct could use a cleaning as well. Ran system for 30 minutes without system shutting off or tripping on any safety. Furnace is 22 years old and replacement is recommended over any repairs. Installed pan switch and signed homeowner up for maintenance membership