Your furnace relies on the heat exchanger to properly warm your home. A cracked heat exchanger releases dangerous fumes into your home, so it’s a problem we recommend addressing right away. How can you tell if a heat exchanger cracked?

Review signs that you’re dealing with a cracked heat exchanger with our team at Service Emperor. Contact us at (912) 231-5430 to set up a repair appointment for your heat exchanger.

How Heat Exchangers Work

Many property owners don’t know exactly what a heat exchanger does. Depending on your understanding of your heating system, you may not have known that your furnace included a heat exchanger.

Each gas furnace contains a minimum of one heat exchanger. The heat exchanger looks like a large set of coils. A furnace heat exchanger carries the heat generated by burning flue gas, allowing the warm air to change the temperature in your home.

A properly functioning heat exchanger provides heat while protecting you from chemical compounds like sulfur dioxide, nitrous oxide, nitrogen dioxide, and carbon monoxide.

Many furnaces have only a single heat exchanger. However, if you have a new furnace or a high-efficiency model, your furnace may contain two heat exchangers.

How to Tell If Your Gas Furnace Has a Cracked Heat Exchanger

The heat exchanger is a vital component in your furnace. However, your furnace may develop cracks but continue running, making it difficult to know when a heat exchanger gets damaged. We recommend keeping an eye out for these signs of a crack.

Your Carbon Monoxide Detector Goes Off

A crack in your heat exchanger often leads to a carbon monoxide (CO) leak. If you have a working CO detector, it should go off, notifying you of this potential health hazard. Note that CO detectors often sound the alarm only when they detect significant amounts of harmful gases.

Take any CO alarm seriously. Contact an HVAC company to have a trained professional assess your whole furnace, looking for any evidence of a crack.

Protect your family by keeping working batteries in your CO detector. We recommend replacing the batteries every six months or when the time changes in spring and fall if you need a reminder. Taking this step helps you keep your family safe.

Family Members Complain of Flu-Like Symptoms

Sometimes, CO and other gases leak out of a malfunctioning heat exchanger in insufficient quantities to set off your CO detector. In other cases, you may not have a working CO detector in your home.

In these situations, signs of illness in your family may become the first sign that you have heat exchanger cracks. Carbon monoxide causes several adverse health effects when inhaled. Monitor your family’s health and seek help if family members complain of:

  • Headaches
  • Drowsiness
  • Dizziness
  • Nausea
  • Breathlessness
  • Problems with vision

In extreme cases, carbon monoxide poisoning leads to unconsciousness and even death. This threat makes keeping your furnace’s heat exchanger in good condition essential.

You Notice Strange Smells

Carbon monoxide gas has no odor. However, some of the other gases emitted by a damaged heat exchanger do generate odors. In some concentrations, people smell carbon dioxide and sulfur dioxide (SO₂), for example.

Many people describe the smell of SO₂ as a just-struck match. If you notice this odor in the air in your home, treat it like a big deal. Reach out to a professional HVAC technician before the gas begins causing illness for your family members.

Malfunctions with Your Heating

Cracked heat exchangers often continue to function long after they begin releasing combustion gases into the air. However, in some cases, they do begin showing signs of a breakdown.

Your entire furnace may stop working in rare cases. In other situations, problems with a furnace heat exchanger cause the system to start short cycling. Short cycling occurs when furnaces turn off before appropriately heating your home.

The Furnace Produces More Soot

A cracked heat exchanger introduces excess carbon into your heating system. Depending upon the extent of the crack, your unit may begin producing excessive amounts of soot, sometimes releasing this byproduct into the air. Incomplete combustion may also increase soot from your furnace.

You also want to check the flame of your furnace if you suspect you have a cracked heat exchanger. Your burners should have a blue flame. If the flame appears yellow, you may be dealing with a leak in the system.

You Find Water Around the Furnace

Water vapor often collects around cracks in a heat exchanger. The water gathers around and under the unit, providing a noticeable sign of an issue with your system.

Causes of a Crack in a Heat Exchanger

Why do some heat exchangers crack, releasing natural gas and other dangerous chemical compounds into your property?


Normal wear and tear represent one of the most common reasons for a cracked heat exchanger. Generally, you can expect a heat exchanger to last for around 15 years. After this point, many furnace components begin to wear out and break.

Over time, the heat inside your furnace causes stress cracks in the heat exchanger’s walls. Manufacturers design the metal to withstand heat, but eventually, even the best-made components wear down.

Limited Airflow

Blockages in your heating and cooling vents often cause pressure to back up in your system. Your furnace must get enough air to function correctly, making it vital that you:

  • Keep your air ducts clean.
  • Change your air filters regularly.
  • Prevent blocked registers.

Allowing obstructions to develop often causes cracks in the metal of the furnace. A poorly maintained system may have more issues with airflow, cracks, and overheating.

Improperly Sized Furnace

Furnaces that are too small to heat your home have higher odds of developing cracks. They pass the high limit to overheat more often, causing repeated damage to the metal. Eventually, the metal snaps, leading to a cracked heat exchanger.

Over-sized furnaces also run the risk of cracking. The heat exchanger in a large heating system ends up turning on and off frequently. The burners get worn out more quickly, and that encourages condensation to form inside, leading to rust.

Options to Handle a Cracked Heat Exchanger

What should you do if you have a cracked heat exchanger? Generally, you cannot repair a broken heat exchanger that releases gas into the air. Instead, you have two options:

Replace the Heat Exchanger

HVAC professionals replace damaged heat exchangers to protect property owners from dangerous CO gas in the air. Crews use a combustion analyzer to identify the issue before beginning replacement. In some cases, crews notice your heat exchanger is cracked during a furnace tune-up.

Replace Your Furnace

A cracked heat exchanger poses serious threats to your health. Issues with the heat exchanger often indicate other problems with your furnace, which may go beyond the scope of a furnace repair. In this situation, a professional may recommend replacing your furnace instead of just the heat exchanger.

Contact Us for Heat Exchanger Replacement

Get help when your heat exchanger cracks by contacting us for HVAC service. Reach the main office for Service Emperor by calling (912) 231-5430. We get your warm air working again and handle all of your air conditioning repairs as well.