Furnace Heat Exchanger Replacement Cost

The heat exchanger separates the burner flames from the air that circulates through your home. A crack can let combustion gases, including carbon monoxide, into the airflow, so a cracked heat exchanger is treated as a safety problem. HomeGuide puts replacement at $1,000 to $3,000, with a national average of $2,000. Angi's average is $1,750, with most homeowners paying $1,250 to $3,000.

Part and labor

Labor makes up most of the cost.

Under warranty vs out of warranty

HomeGuide notes warranties usually cover the part only, not labor. Check the furnace's warranty registration before paying.

Other heat exchanger types

Other costs

Repair or replace the furnace?

HomeGuide says technicians usually replace rather than repair heat exchangers. It recommends replacing just the heat exchanger only when the furnace is under 10 years old with no other problems and the job costs much less than a new furnace. HomeGuide lists furnace replacement at $3,500 to $7,500+. See furnace replacement cost.

Signs of a cracked heat exchanger

• A carbon monoxide alarm going off.
• Soot around the burners or unusual flame color.
• A burning or chemical smell when the furnace runs.
• Visible cracks or rust found during an inspection.

If a CO alarm sounds, leave the house and call for help. Angi notes gas and oil furnace inspections include carbon monoxide testing; see furnace tune-up cost.

What the heat exchanger does

The heat exchanger separates the burner flame and combustion gases from the air that flows through the house. Air passes over its outside surface and warms up, while the exhaust stays inside and is vented outdoors.

Why a crack is serious

A crack or hole can let combustion gases, including carbon monoxide, mix with the household air. That is why many technicians will shut down a furnace with a cracked heat exchanger. Every home with a gas furnace should have working carbon monoxide detectors.

Signs of a problem

• Soot or rust inside the furnace cabinet.
• Burner flames that waver or change when the blower starts.
• A carbon monoxide alarm going off.
• The furnace shutting down on its high-limit safety switch.

Getting a second opinion

A cracked heat exchanger is a costly finding, and it can be hard to see. It is reasonable to ask for photos or a camera inspection, and to get a second opinion before paying for replacement.

Replace the part or the furnace?

Replacing a heat exchanger requires taking much of the furnace apart, so labor is significant. If the furnace is out of warranty or older, many homeowners choose to replace the whole furnace instead. If the part is still under warranty, the repair can make more sense.

Questions to ask

1. Can you show me the crack in a photo or video?
2. Is the heat exchanger still under the manufacturer's warranty?
3. How does the repair cost compare with a new furnace?

In Texas

Furnaces in Texas often run fewer hours than those in northern states, but they still age. A fall inspection that includes the heat exchanger is the best way to catch a problem before the furnace is used on cold nights.

How a cracked heat exchanger is found

A technician cannot always see a crack, so a proper inspection uses several methods:

• Visual inspection with a light or camera through the burner openings or after removing parts.
• Combustion analysis, which measures gases in the flue and can show changes when the blower starts.
• Flame behavior, where a flame that wavers or changes when the blower turns on can indicate air leaking through a crack.
• Carbon monoxide testing in the supply air and around the furnace.

A diagnosis based on a single test is less reliable. If a technician says your heat exchanger is cracked, ask which tests they used and for photos or video of the crack.

Why cracks happen

Heat exchangers heat up and cool down with every cycle. Over many years, this expansion and contraction stresses the metal. Problems that make the furnace run hotter, like a dirty filter, blocked vents, an oversized furnace or poor airflow, increase the stress and can cause cracks sooner. Corrosion from condensation can also weaken the metal.

Safety first

A cracked heat exchanger can let combustion gases, including carbon monoxide, mix with the air circulating through the house. Not every crack causes a leak, but the risk is serious enough that a technician may shut the furnace off and tag it as unsafe. Carbon monoxide detectors on every floor and near bedrooms are essential in any home with a gas furnace.

Warranty

Many furnace manufacturers give longer warranties on the heat exchanger than on other parts, sometimes twenty years or a lifetime for the original owner. Check the furnace's warranty and registration before paying. Even if the part is covered, labor may not be, and labor for this job is substantial.

More on replace the part or the furnace

Replacing a heat exchanger is a major job that involves taking much of the furnace apart. If the part is not covered by warranty, the total cost can approach a new furnace. On an older furnace, replacement often makes more sense. On a newer furnace with a covered part, replacing the heat exchanger may be the better value.

Ask for proof

Ask for photos or video of the crack and the test results.

More on getting a second opinion

Because the repair is costly and the diagnosis can be hard, a second opinion from another licensed technician is reasonable before you decide.

Sources

1. HomeGuide: How Much Does a Heat Exchanger Replacement Cost? (Jun 23, 2025)
2. Angi: How Much Does It Cost to Replace a Heat Exchanger? (updated Apr 6, 2026)
3. Angi: How Much Does a Furnace Inspection Cost? (updated Jul 9, 2026)