Cracked heat exchanger? It gets red-tagged.
A cracked heat exchanger is not a repair I put on the fix-it-later list. Carbon monoxide is colorless, odorless, and at high enough levels fatal. When I confirm a crack, I red-tag the furnace, and it does not run again until the heat exchanger is replaced or the furnace is.
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Older furnaces, older heat exchangers
- Furnaces from the 1970s to 1990sThe 80 percent AFUE furnaces from that era have heat exchangers approaching 30 to 40 years old.
- Over 20 years with no recent analysisSchedule a combustion analysis before this heating season.
- Restricted airflowDirty filters, blocked vents or a failed blower overheat the heat exchanger and speed up cracking.
- Thermal cyclingEvery cycle it expands and contracts. After 15 to 25 years, cracks start at the stress points.
- CO alarm or yellow flameShut the furnace off and call 405-375-4822. Do not restart it.
- Delayed ignitionA bang at startup stresses the heat exchanger every time it happens.
Analyzer, camera, then a straight answer
- Full fireThe furnace runs at full fire while I test.
- Every passageA combustion analyzer samples for CO at every heat exchanger passage and port.
- Supply airI also sample the supply air stream you breathe.
- Camera inspectionWith the burners off, a camera looks for cracks, rust perforation or separation at the stress points.
- Confirmed crackRed tag. The furnace does not run again until it is repaired or replaced.
What heat exchanger work costs in Oklahoma
Plus the $99 dispatch on every visit. Repair or replacement work is quoted in writing before approval.
| Item | Typical price |
|---|---|
| Combustion analysisCO, CO2, O2, flue temperature, efficiency. | $195 |
| CO crack detection diagnosticCombustion gas leak detection at all passages. | $345 |
| Heat exchanger clean and inspectFull visual and combustion inspection. | $395 |
| HX replacement, 80% AFUE, warrantyManufacturer provides the part. Labor only. | $1,895 |
| HX replacement, 80% AFUEParts and labor, non-warranty. | $2,295 |
| HX replacement, 90%+ AFUEParts and labor, includes the secondary heat exchanger. | $2,695 |
| Secondary HX, 90%+ furnaceThe condensing section of a high-efficiency furnace. | $1,195 |
| OEM inducer motorSingle or two stage, 80% or 90% furnace. | $1,084 to $2,250 |
| OEM pressure switchSingle or dual port. | $477 to $539 |
The right call depends on age
Under 15 years old with a valid warranty, replacing the heat exchanger is the right call. Twenty years or more, no warranty, and an aging blower and controls: replacing the whole furnace usually makes more financial sense, and it comes with a fresh manufacturer warranty.
Replace the HX
The manufacturer supplies the part. You pay labor.
$1,895 laborRebuild
Replace the major components and keep the rest, against $15,000 to $30,000 for a full replacement.
$3,500 to $5,500 installedHow a rebuild worksReplace the furnace
A new high-efficiency furnace, sized for the house.
Estimate freeFurnace installationWhat customers say
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Katie B. · Google review · May 2025
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Straight answers
What is a heat exchanger and why does it matter?
It is the metal chamber that separates combustion gases from the air you breathe. Exhaust passes inside, the blower pushes house air across the outside. If it cracks, carbon monoxide can enter your living space. This is a life-safety issue.
What causes a heat exchanger to crack?
Age and thermal cycling. It expands every time the furnace fires and contracts when it shuts off. After 15 to 25 years, cracks develop at stress points. Overheating from dirty filters, blocked vents or a failed blower speeds it up.
How do you detect a cracked heat exchanger?
A CO and combustion gas leak test with an analyzer at each passage while the furnace runs at full fire, plus a camera inspection with the burners off. A confirmed crack means a red tag.
What does heat exchanger replacement cost in Oklahoma?
Warranty replacements where the manufacturer provides the part run $1,895 in labor. Non-warranty replacements are $2,295 for 80 percent AFUE furnaces and $2,695 for 90 percent plus. On furnaces 15 or more years old, replacing the whole furnace is often the better choice.
What does the inducer motor have to do with it?
The inducer pulls combustion gases through the heat exchanger and out the flue before the burners fire. A failed inducer almost always trips a pressure switch and locks out the heat. Inducer replacements run $1,084 to $2,250.
My CO alarm is going off. What do I do?
Get everyone out of the house and call 911. Do not restart the furnace. Once it is safe, call me at 405-375-4822.
Get it tested before winter
If it has not had a combustion analysis recently, schedule one before the first cold snap. It is the most important HVAC inspection an older home can get.
Call 405-375-4822Kingfisher, Enid, Yukon, Mustang, Edmond, Guthrie, El Reno and every town between. Counties: Kingfisher, Canadian, Oklahoma, Garfield, Major, Logan, Blaine.
