A furnace is almost always a background player for your home, helping keep you warm in the cold winter months. It frequently isn't noticed until something goes wrong. 

One root cause may be that your furnace has a cracked heat exchanger. It can be a safety risk, so it’s worthwhile to learn the evidence of a cracked heat exchanger and what you can do if you suspect that may be the problem.  

What Is a Heat Exchanger in a Furnace? 

A heat exchanger transfers heat from the combustion chamber of your furnace to the air that flows throughout the system. It usually accomplishes this with coils or tubes that heat up the air while serving as a barrier to keep gas created in the combustion chamber, called flue gasses, from leaking out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Because of its important role, it’s no surprise that a damaged heat exchanger can pose a risk. Cracks in the heat exchanger can enable dangerous gasses – such as carbon monoxide, which can be lethal – to circulate across your home. 

For obvious reasons, don't ever turn on your furnace if you believe you're dealing with a cracked heat exchanger, as this could make your entire family sick. Contact an HVAC professional right away if you think your heater has a cracked heat exchanger that needs repair. 

Four Warning Signs of a Cracked Heat Exchanger: 

  • Furnace shuts off: A crack in your heat exchanger could cause your furnace to shut off. 
  • Unusual Smells: If the air escaping your furnace has a strong chemical odor, it may be evidence gas is slipping through cracks in your heat exchanger. These byproducts, which may smell like formaldehyde, are a major warning sign. 
  • Carbon monoxide alarm initiates or you feel health problems: If a cracked heat exchanger is relieving carbon monoxide into your home, your carbon monoxide alarm could go off or household members may start experiencing signs of carbon monoxide poisoning. Side effects include headaches, dizziness, weakness, nausea, vomiting or feeling drowsy. If the alarm goes off or you feel unusually tired, exit the home immediately and then call for help. 
  • Soot: If you spot black sooty accumulating around the exterior of your furnace, it’s an indication something could be seriously wrong.

What You Should Do if Your Furnace Heat Exchanger is Cracked 

If you worry your furnace has a cracked heat exchanger, call a pro with extensive experience in furnace installation Phoenix as soon as possible so they can examine your system and, if needed, perform a furnace heat exchanger replacement. Costs often fluctuate depending on the situation, but estimates run in the neighborhood of $1,000 to $3,000. 

However, the good news is that heat exchangers are regularly covered by the warranty. You’ll want to confirm the warranty paperwork on your furnace, because while the warranty might not cover the entire cost of repairs, it could significantly reduce your bill.  

How to Prevent a Cracked Heat Exchanger in Your Home  

One of the most convenient ways to minimize the risk of problems in your furnace overall is via regular furnace maintenance. Furnaces work the best when they work efficiently. Contacting a skilled professional to examine your furnace for broken-down parts, dirty filters and other common problems can help you avoid getting a big bill later on.  

It’s also a good idea to inspect your furnace filters every few months – it’s recommended some filters be changed every 90 days or sooner if they are dirty or grimy. While the filters aren't a part of the heat exchanger itself, the strain of dragging air through a clogged filter makes the entire furnace work harder to do its job. And the harder your furnace has to work, the more deterioration pieces like the heat exchanger will endure.