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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The $79 trip charge on a Hopkins furnace repair is waived as soon as you approve the work, and you see the written price before any of it starts. That includes condos and apartments where the furnace lives in a hallway closet.
Two kinds of furnace calls come up often in Hopkins. The first is the tight basement near Mainstreet, where the furnace sits wedged against the water heater and a blower motor or inducer swap takes some planning just to get the old part out the front. The second is the condo or apartment closet furnace. Those units breathe through a louvered door, share space with storage and often drain into a small condensate pump, so many of our fixes there come down to airflow, combustion air and drainage.
The 1950s and 1960s ramblers around Interlachen Park usually have roomier basements and a furnace on its second or third generation. Near Minnehaha Creek, damp lower levels leave rust on burners and flame sensors, and a sensor coated with corrosion is a common reason a furnace lights, runs a few seconds and shuts down.
Updated October 27, 2026
National averages (HomeGuide, 2026), not our prices: a flame sensor $80–$250, a pressure switch $150–$400, a limit switch $100–$375. More in the furnace repair cost guide.
Symptom guides: Blinking light codes · Pressure switch trips · Strange noises · Leaking water · Signs your furnace needs a technician
Mostly airflow and air supply. A closet furnace needs the louvered door or grilles the installer provided, and boxes stacked against it starve the burners and the blower. Filters in those slide-in slots get forgotten. Many closet units drain into a condensate pump, and when its float sticks, the safety switch shuts the furnace down. Check the filter and the pump first. If your association controls the vent or roof, we'll coordinate with them.
Yes. Most repairs, including the igniter, flame sensor, inducer, pressure switch and control board, happen through the front panel. A blower motor is the tricky one, because the blower assembly slides out the front and needs about a furnace's depth of clear floor. Moving storage and laundry baskets out of the way before we arrive saves time. If a furnace truly can't be serviced where it sits, that matters for the next replacement.
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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