I found this on my afternoon inspection today. As per my normal routine, I fired up the furnace at the end of the inspection. But, I noticed this scorch mark during my visual inspection of the furnace. The furnace fired up and was running for about 5 minutes before I snapped this image (back side of gas fired forced air furnace).
Funny thing is the the Agent broke out the sellers disclosure and it had a reciept from a HVAC technician that clearly indicated that the furnace was functional and safe to operate. How could the Tech have missed the big scorth mark in the back of the furnace is beyond me.
Anyways, any ideas as to possible cause? Cracked heat exchanger, maybe? For you HVAC Gurus out there