A furnace is often a background player at home, helping keep you warm across the cold winter months. It frequently won't be noticed until a malfunction appears. 

One cause may be that your furnace has a cracked heat exchanger. It can potentially be hazardous, so it’s critical to learn the signs of a cracked heat exchanger and what to do if you suspect that is the problem.  

What Is a Heat Exchanger in a Furnace? 

A heat exchanger helps transition heat from the combustion chamber in your furnace to the air that moves throughout the air ducts. It typically does this using coils or tubes that heat the air while functioning as a barrier to keep the gasses formed in the combustion chamber, called flue gasses, from getting out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Given its central role, it’s no surprise that a damaged heat exchanger can be hazardous. Cracks in the heat exchanger can enable dangerous gasses – such as carbon monoxide, which can be lethal – to flow through your home. 

For obvious reasons, don't ever turn on your furnace if you suspect there's a crack in the heat exchanger, as letting it run could make the entire family ill. Call an HVAC professional as soon as possible if you are worried your heating has a cracked heat exchanger that should be repaired. 

Four Signs of a Cracked Heat Exchanger: 

  • Furnace turns off: Cracks in the heat exchanger can cause your furnace to turn off. 
  • Strange Smells: If the air escaping your furnace has an intense chemical scent, it may be a sign gasses are seeping through cracks in your heat exchanger. These byproducts, which will often smell like formaldehyde, are a common warning sign. 
  • Carbon monoxide alarm initiates or you recognize symptoms of poisoning: If a cracked heat exchanger is emitting carbon monoxide inside your home, your carbon monoxide alarm should go off or household members could experience signs of carbon monoxide poisoning. Symptoms include headaches, dizziness, weakness, nausea, vomiting or feeling drowsy. If your alarm goes off or you feel unusually tired, get out of the home right away and then call for help. 
  • Soot: If you notice black sooty collecting near the exterior of your furnace, it’s another sign something may be seriously wrong.

What You Can Do if a Furnace Heat Exchanger is Cracked 

If you suspect 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, start a furnace heat exchanger replacement. Costs often differ 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 covered by the warranty. It's a good idea to check the warranty paperwork on your furnace, since while the warranty might not cover the entire cost of repairs, it still may significantly lower your bill.  

How to Avoid a Cracked Heat Exchanger in Your Home  

One of the most convenient ways to minimize the risk of problems in your furnace overall is with routine furnace maintenance. Furnaces provide the best possible return on investment when they operate efficiently. Calling a trained professional to examine your furnace for broken-down parts, clogs in the air filters and other likely problems can help you avoid getting a big bill later on.  

It’s also helpful to review your furnace filters every few months – it’s ideal some filters be changed every 90 days or sooner if they are dirty or grimy. While the filters are not part of the heat exchanger itself, the strain of drawing air through a clogged filter makes the entire furnace work harder to complete its job. And the harder your furnace needs to run, the more deterioration parts like the heat exchanger will sustain.