What is a cracked heat exchanger and can it be fixed?
The heat exchanger is composed of one or more chambers in which the fuel is burned and through which superheated exhaust gases travel. The fan blows air around the chamber(s) to pick up heat and bring it into the house. When a crack develops exhaust gas can escape into the house. A cracked heat exchanger cannot be properly repaired by any accepted trade practice. The heat exchanger must be replaced. If the furnace is very old then the heat exchanger may not be available. In such instances the entire furnace must be replaced. Even if the heat exchanger is available it’s not always cost effective to replace it. Pictures and further explanation can be found here.
