Thermostat Came out today to install 3 nest thermostats provided by the homeowner. I installed all 3 thermostats, set the equipment details, and the homeowner set them up for his Nest app. While making wire changes in the furnace control boards, I noticed the basement system had a burnt high limit switch. This equipment is 22 years old, Trane gas furnace. I performed a safety check on the heat exchanger after observing no burnt high limit. The heat exchanger has multiple cracks in it and is no longer safe to heat the home. I also observed that the blower wheel was dirty and the blower motor was seeping oil at the main seal, the igniter and flame rectifier are both weak and corroded, weak inducer that is over amping and has worn bearings, and no wet switch or emergency drain pan. At 22 years old this equipment is well past average life expectancy and has multiple weak/original components that are subject to failure at anytime. Due to the age, condition, and safety concern, I recommende