A very well known HVAC company that has serviced this house for years sent a tech this morning to look at the blower. After be removed a small piece of debris from the blower it was fine. He then checked the burners and noticed that, when the blower came on, the flame on one of the burners was "rolling out the bottom" He then said the exchange was cracked and, with a unit 20 years old, it's just a matter of time before it fails which could release carbonmonoxide into the house.
Originally posted by Irascible
BTW: Who said the heat exchanger was cracked? Did they document the exact location(s) of the crack? Did they show you? Has anyone else confirmed the existence of those cracks?