San Antonio · Heat Exchanger Inspection & Replacement · Same-Day Service
A cracked heat exchanger can leak carbon monoxide into your home — it's the one furnace failure we treat with zero tolerance. Sometimes it's a $1,500 part swap; sometimes it means replacing the furnace. We'll show you photos and give you the straight math.
Typical price
$2,500–$4,500 repair; $3,500–$5,500 full replacement
Level IV · Critical System Repair
Time to fix
4–8 hours for heat exchanger swap; 6–10 hours for full replacement
Same-day available
Urgency
Critical — CO safety. Furnace stays off until repaired or replaced.
Free diagnostic · Written price before any work · No call center — Clint or one of his sons picks up
15+
Years in San Antonio
Same-Day
Service window
$0
Diagnostic fee
TACLB29435E
Texas Master License
The heat exchanger is the metal chamber that separates the combustion side of your furnace (hot gases from burning fuel) from the air side (the air that gets blown into your house). When it cracks, those combustion gases — including carbon monoxide — can leak into your supply air.
Cracked heat exchangers are serious. CO is colorless, odorless, and deadly. If we find a crack, we red-tag the furnace and shut it down until it's fixed. No exceptions, no 'just run it for the weekend.'
The math: replacement heat exchangers are $1,200–$2,800 part-only, plus 4–8 hours labor — usually $2,500–$4,500 installed. On a furnace under 10 years old with good parts coverage, repair makes sense. On a furnace older than 12–15 years, you're usually money ahead replacing the whole thing for $3,500–$5,500. We'll show you photos and walk through the numbers honestly.
What it costs in San Antonio
$2,500–$4,500 repair; $3,500–$5,500 full replacement — We'll give you the math on repair vs. full replacement. On older furnaces, replacement is usually smarter. Diagnostic is free and the written price comes before any work — you only pay if you green-light the fix.
Repair Tier · $2,000+
Critical System Repair
Repair vs. replacement — how our flat-rate pricing works
If two or more of these sound familiar, it's probably your heat exchanger inspection & replacement.
Want a written price today?
Snap the data plate, send it to (210) 600-5091. We'll text back a real price range — usually within an hour during business hours.
Here's exactly what a Carnes and Sons tech does at your house — no mystery, no upselling.
Camera through the burner area and inducer port to look at every accessible surface of the heat exchanger. We photograph everything.
Measure CO in supply air with a calibrated combustion analyzer. Any CO crossover above safe limits is conclusive evidence of a crack.
With the blower running, watch the burner flame. A flame that flickers or distorts when the blower kicks on indicates a crack letting blower air pressurize the combustion chamber.
Pull the model number, check warranty coverage, get the part price, and compare to a new furnace installed. We present both options and let you decide — no pressure.
Heat Exchanger Inspection & Replacement repair on residential systems from every major manufacturer — same parts inventory on the truck, same flat price.
Don't see your brand? If it's residential split-system or package, we work on it. Most heat exchanger inspection & replacement parts are universal — what changes is the wiring diagram, not the part.
Yes. Carbon monoxide can leak into your supply air and into your home. CO poisoning kills hundreds of Americans every year. We don't take chances — if we find a crack, the furnace stays off until it's fixed or replaced.
$2,500–$4,500 installed in San Antonio. The part alone is $1,200–$2,800 depending on furnace brand. On older furnaces, full replacement at $3,500–$5,500 is usually the smarter financial choice.
Often yes. Most manufacturers warranty heat exchangers for 20 years or lifetime to original owner. We always check warranty status before quoting and pass through any covered parts cost. Labor is usually not covered.
Yes — we use a borescope camera and photograph the exchanger. You see exactly what we see. We do not condemn heat exchangers without proof.
Absolutely get one. We'll give you our photos and combustion analysis readings to share. Any honest tech should reach the same conclusion. The only people we worry about are the ones who push for replacement without proof.
15–25 years typically. Oversized or short-cycling furnaces wear them out faster. Annual maintenance with combustion analysis catches early signs of trouble.
No. CO detectors only alarm at high levels — by the time they go off you've already had unsafe exposure. And running a cracked furnace risks fire damage to the surrounding cabinet. We'll red-tag the unit until it's safe.
If yours is 12+ years old, yes — almost always. New furnaces are 95–97% efficient (vs. 80% on old units), come with full warranty, and the heat exchanger isn't the only old part. $3,500–$5,500 for a complete replacement vs. $2,500–$4,500 for one part on an old unit is usually a no-brainer.
We're based in Stone Oak and roll trucks across San Antonio and the surrounding Hill Country every day.
License TACLB29435E · Family-Owned Since 2010
Cities & neighborhoods we serve
San Antonio · Stone Oak · Alamo Heights · Hollywood Park · Hill Country Village · Shavano Park · Castle Hills · Leon Valley · Helotes · Boerne · Fair Oaks Ranch · Bulverde · Timberwood Park · Garden Ridge · Schertz · Cibolo · Selma · Universal City · Live Oak · Converse · Windcrest · New Braunfels
No call center. The owner or one of his sons picks up.
(210) 600-5091