We came out for no cool on Lennox unit from 2012. We found high limit switch was tripped. We reset the switch and system tried to kick on. System eventually came on, but the fan did not immediately start. After several seconds the fan kicked on and system was cooling. Unfortunately it ran for about 10 minutes and the high limit switch tripped again due to extreme heat the fan motor was producing. The capacitor is out of tolerance and contactor is heavily pitted showing signs of failure. The condenser coils are extremely impacted with dirt and debris causing major air flow issues. We inspected the furnace and found the evaporator coil has major biological growth underneath it. The blower wheel has dirt and debris buildup. Furnace also has single wall flu pipe and tape around it, both major code and safety violations. Condensation pump is extremely dirty and furnace does not have drain line switch and has high static pressure of .9. Customer is getting a quote on replacing system.