Home inspectors do not dismantle appliances to determine their condition. Because the furnace heat exchanger is not directly visible, we use a method of testing in an effort to identify cracked heat exchangers:
- Turn the thermostat up, wait for the burners to ignite.
- After the burners ignite wait for the blower to start.
- If when the blower starts, if the burner flames change color, shape, or flicker, the heat exchanger may be cracked, and you should recommend service by a qualified HVAC contractor. Do not state that the exchanger is cracked, only that it may be, due to the change in burner flame color at blower activation.