10/31/2026
How Do I Know If My Heat Exchanger Is Cracked? ☕️ SATURDAY MORNINGS: Ask Lee!
Every Saturday morning, Lee answers one of your real HVAC questions right here.
Today’s Question:
“Lee — I keep hearing that a cracked heat exchanger is dangerous. How would I even know if mine was cracked?”
Lee’s Answer:
This is an important question — and the honest answer is that most homeowners can’t tell on their own. A cracked heat exchanger doesn’t usually announce itself with obvious symptoms until the crack is significant. That’s why professional inspection matters.
That said, here are the signs worth paying attention to:
🔴 **Carbon monoxide detector alarm.** This is the most serious signal. If your CO detector goes off when your furnace is running, leave the house immediately and call 911. Don’t go back in until it’s been inspected.
⚠️ **Yellow or orange burner flame instead of blue.** A properly burning gas furnace has a steady blue flame. Yellow or orange flames can indicate incomplete combustion — sometimes associated with heat exchanger issues.
⚠️ **Soot or black marks around the furnace.** Can indicate combustion gases escaping where they shouldn’t.
⚠️ **Physical symptoms when the heat runs.** Headaches, dizziness, nausea, or fatigue that improve when you leave the house and return when you come back can be symptoms of low-level carbon monoxide exposure. Take these seriously.
⚠️ **Furnace that’s 15+ years old.** Heat exchangers can develop cracks from years of thermal expansion and contraction. Older systems warrant closer inspection.
The most reliable way to know is a professional inspection with proper equipment — which is exactly what a fall tune-up includes. If it’s been more than a year since your furnace was inspected, schedule one before you rely on it this winter.
🙋♂️ Drop your question in the comments for next Saturday. 👇
