Cracked Heat Exchanger: Symptoms and How It's Confirmed
Signs of a cracked furnace heat exchanger, how a technician confirms it with a camera and CO readings, what to do after a red tag, and repair vs replace.
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Furnace repair in Independence, on propane or natural gas, starts with a $79 trip charge, waived when you approve the repair. On acreage we rule out a low tank or regulator first.
Independence furnace calls rarely look like suburban ones. Many homes run propane, so a no-heat call can start with a tank that ran low or a regulator problem before we ever open the furnace. Mechanical rooms often share space with a well pressure tank, a water softener and piping added over the decades, which means extra humidity, the odd leak onto the furnace base and cramped service access. Farmhouses with additions from different eras can have a furnace pushing air through ductwork stretched to rooms it was never meant to reach.
The larger newer homes on wooded lots may have two furnaces or a zoned system, with condensing furnaces venting through PVC out a side wall. On open ground, those pipes can drift over in a storm. Mice are a fact of rural life too, and a nest in a burner compartment, an intake pipe or a barn unit heater is a common fall problem out here.
Updated November 10, 2026
National averages (HomeGuide, 2026), not our prices: a variable-speed (ECM) blower motor $800–$2,300, an igniter $100–$250, a flame sensor $80–$250. More in the furnace repair cost guide.
Symptom guides: Carbon monoxide · Blowing cold air · Won't ignite · Short cycling · Signs your furnace needs a technician
Yes. Gas and propane unit heaters and radiant tube heaters are furnaces in a different box, and they fail in similar ways: dust and cobwebs on the burners, a mouse nest in the housing, a worn igniter or a vent problem. Clean the area around the heater before the season starts. One visit can cover both the house furnace and the barn heater.
It can. A sweating pressure tank and a softener that occasionally leaks add moisture that rusts the furnace base and burners. Bags of softener salt stacked against the cabinet shed corrosive dust, and the furnace may draw that air for combustion. Keep salt and storage away, leave the front of the furnace clear for service, and tell us about any past water on the floor so we check the cabinet bottom and wiring.
Signs of a cracked furnace heat exchanger, how a technician confirms it with a camera and CO readings, what to do after a red tag, and repair vs replace.
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