A furnace is almost always a background player in your home, ensuring you're warm during the cold winter months. It frequently isn't noticed until something breaks down. 

One cause may be that your furnace has a cracked heat exchanger. It’s a potentially dangerous issue, so it’s critical to know the symptoms of a cracked heat exchanger and what you should do if you suspect that may be the problem.  

What Is a Heat Exchanger in a Furnace? 

A heat exchanger helps transition heat from the combustion chamber of your furnace to the air that flows inside the ventilation. It usually accomplishes this using coils or tubes that warm the air while serving as a barrier to keep byproducts created in the combustion chamber, called flue gasses, from getting out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Thanks to its central role, it shouldn't come as a surprise that a damaged heat exchanger can pose a risk. Cracks in the heat exchanger can permit dangerous gasses – like carbon monoxide, which can be lethal – to circulate throughout your home. 

For this reason, do NOT turn on your heater if you think you're dealing with a cracked heat exchanger, as doing so could make the entire family ill. Reach out to an HVAC professional immediately if you think your heating has a cracked heat exchanger that should be repaired. 

Four Symptoms of a Cracked Heat Exchanger: 

  • Furnace turns off: A crack in your heat exchanger can cause your furnace to switch off. 
  • Odd Smells: If the air coming out of your furnace has a powerful chemical scent, it could be a sign gasses are seeping through cracks in your heat exchanger. These byproducts, which may smell like formaldehyde, are a common warning sign. 
  • Carbon monoxide alarm initiates or you notice poisoning symptoms: If a cracked heat exchanger is relieving carbon monoxide into your home, your carbon monoxide alarm should go off or family members might struggle with signs of carbon monoxide poisoning. Symptoms include headaches, dizziness, weakness, nausea, vomiting or feeling tired. If an alarm goes off or you feel sick, get out of the home right away and then call for help. 
  • Soot: If you notice black sooty buildup around the exterior of your furnace, it’s an indication something could be seriously wrong.

What You Can Do if a Furnace Heat Exchanger is Cracked 

If you believe your furnace has a cracked heat exchanger, contact a professional well versed in furnace installation Mission Viejo right away so they can take a look at your system and, if necessary, handle a furnace heat exchanger replacement. Costs should vary depending on the situation, but estimates often hover around $1,000 to $3,000. 

Estimates aside, the good news is that heat exchangers are often protected by the warranty. You should check the warranty paperwork on your furnace, as while the warranty might not cover the entire cost of repairs, it can significantly lower your bill.  

How to Prevent a Cracked Heat Exchanger in Your Home  

One of the easiest ways to minimize the risk of problems in your furnace overall is via consistent furnace maintenance. Furnaces work the best when they run efficiently. Hiring a trained professional to check your furnace for worn-out parts, dirty filters and other potential problems can help you avoid getting a big bill later on.  

It’s also a good idea to take a look at your furnace filters every few months – it’s encouraged some filters be changed every 90 days or sooner if they are dirty or grimy. While the filters aren't connected to the heat exchanger itself, the strain of dragging air through a clogged filter makes your entire furnace work harder to complete its job. And the harder your furnace works, the more strain parts like the heat exchanger will sustain.