3 Signs Of A Bad Heat Exchanger

The heat exchanger in your furnace is responsible for allowing the transfer of heat, while preventing dangerous exhaust fumes from entering your home. Unfortunately, heat exchangers are liable to develop cracks and other problems that can compromise their ability to restrict the flow of those deadly exhaust gases. If you would like to learn more about how HVAC professionals can recognize a bad heat exchanger, read on. This article will discuss three common signs.


Cracks are the most basic and also the most drastic sign of a damaged heat exchanger. Over time, the constant exposure to heat and caustic substances will cause the thin metal walls of the exchanger to develop cracks. Such cracks often appear along the exchanger’s seams. The larger the crack, the easier it is to detect by means of visual inspection. Yet furnace repair people can also utilize infrared light detectors to find cracks.


Some cracks are simply too small and thin to be directly observed. Such cracks are often easier to diagnose by means of discolorations in the surrounding metal. These discolorations are the result of soot that has escaped and built up around the crack. Thus any inexplicable dark spots may indicate an area where gases are escaping from the heat exchanger.

Odd Furnace Flame Behavior

A cracked heat exchanger allows the combustion air from inside your furnace to mix with the air being sent up into your home. As these two streams of air come together, they can cause inexplicable changes in the behavior of your furnace flame. An experienced furnace technician can often diagnose exchanger problems simply by observing the flame. If it starts jumping and dancing around when the blower fan engages, this is a strong sign that combustion air is escaping from the heat exchanger.

If you believe that your heat exchanger may be suffering from cracks, contact the experts at Metro Heating & Cooling for an immediate consultation.