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3 Signs Of A Bad Heat Exchanger

The heat exchanger in your furnace is responsible for transferring the heat, while preventing dangerous exhaust fumes from entering your home – so what are the 3 signs of a bad heat exchanger?

Unfortunately, over time, heat exchangers can develop cracks and other problems that can compromise their ability to restrict the flow of those deadly exhaust gases.

1. Cracks

  • A cracked heat exchanger is one of the most basic and common symptoms, and also often the most drastic sign of a damaged heat exchanger

Over time, the constant exposure to heat and other caustic substances causes the thin metal walls of the heat exchanger to develop cracks.

These cracks often appear along the heat exchanger’s seams.

Understandably, the larger the crack, the easier it is to detect by means of visual inspection.

Furnace repair technicians can also utilize infrared light detectors to find cracks if they are not visible with the naked eye.

2. Discoloration

  • Sometimes a cracked heat exchanger has cracks that are simply too small and thin to be directly observed

These cracks are often easier to diagnose by looking for discoloration in the surrounding metal, which is the result of soot that has escaped and built up around the crack.

Any inexplicable dark spots may indicate an area where gases are escaping from the heat exchanger.

3. 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 heat exchanger problems simply by observing the flame.

If the flame starts jumping and dancing around when the blower fan engages, this is a strong sign that combustion air is escaping from the cracked heat exchanger.


If any of these 3 signs of a cracked or bad heat exchanger sound familiar, and you believe that your heat exchanger may be suffering from cracks, discoloration or has odd flame behaviour, simply Contact Us at 651-294-7798 for an immediate consultation.

We’ll make sure that your heat exchanger is working properly again in no time.

We cover Blaine, Bloomington, Brooklyn Park, Eagan, Edina, Hastings, Maplewood, Minneapolis, Minnetonka, Roseville, North Saint Paul, Saint Paul, Saint Paul Park, South Saint Paul, Stillwater, West Lakeland, West Saint Paul, White Bear Lake, Woodbury, and many more locations.

Can’t find your town listed? Contact us at 651-294-7798 to tell us where you live, so we can help you.

Schedule a HVAC repair anywhere in the Minneapolis or St. Paul area today by calling (651) 294-7798 or by requesting an estimate online.


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1220 Cope Avenue East, Maplewood, MN 55109