A furnace is often a background player in your home, keeping you warm across the cold winter months. It frequently doesn’t get noticed until a malfunction appears. 

One root cause could be that your furnace has a cracked heat exchanger. It can potentially be hazardous, so it’s worthwhile to familiarize yourself with the evidence of a cracked heat exchanger and what you should do if you believe that may be the problem.  

What Is a Heat Exchanger in a Furnace? 

A heat exchanger helps move heat from the combustion chamber of your furnace to the air that moves inside the ventilation. It generally does this using coils or tubes that heat 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? 

Given its central role, it isn't surprising that a damaged heat exchanger can be very dangerous. A crack in the heat exchanger can allow dangerous gasses – such as carbon monoxide, which can be lethal – to circulate across your home. 

For obvious reasons, never run your furnace if you believe there's a crack in the heat exchanger, as doing so could make the entire household sick. Call an HVAC professional immediately if you are worried your heater has a cracked heat exchanger that needs repair. 

Four Warning Signs of a Cracked Heat Exchanger: 

  • Furnace shuts off: Cracks in the heat exchanger can cause your furnace to turn off. 
  • Odd Smells: If the air leaving your furnace has a strong chemical scent, it might be an indicator that gas is leaking through cracks in your heat exchanger. These byproducts, which will often 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 inside your home, your carbon monoxide alarm should go off or family members may start experiencing signs of carbon monoxide poisoning. Side effects include headaches, dizziness, weakness, nausea, vomiting or feeling drowsy. If your alarm goes off or you feel unwell, leave the home immediately and then call for help. 
  • Soot: If you notice black sooty collecting near the exterior of your furnace, it’s an indication something might be seriously wrong.

What to Do if a Furnace Heat Exchanger is Cracked 

If you believe your furnace has a cracked heat exchanger, call a pro experienced in furnace installation Bishop right away so they can take a look at your system and, if needed, start a furnace heat exchanger replacement. Costs should fluctuate depending on the situation, but estimates run in the neighborhood of $1,000 to $3,000. 

Estimates aside, the good news is that heat exchangers are often included in the warranty. You should review the warranty paperwork on your furnace, as while the warranty won't always cover the entire cost of repairs, it can significantly shrink your bill.  

How to Prevent a Cracked Heat Exchanger in Your Home  

One of the easiest ways to prevent a problem in your furnace overall is via routine furnace maintenance. Furnaces offer the most benefits when they run efficiently. Contacting a skilled professional to check your furnace for old parts, clogs in the air filters and other common problems can keep you from getting a big bill later on.  

It’s also helpful 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 drawing air through a clogged filter makes your entire furnace work harder to do its job. And the harder your furnace has to work, the more wear and tear components like the heat exchanger will experience.