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 Minnetonka starts with a $79 trip charge, waived when you approve it, including storm-tripped boards on wooded streets. After storms on wooded streets, control boards that won't restart cleanly are a common call.
Minnetonka's houses spread out on hilly, wooded lots, and that shapes both the furnace calls and the winters they come in. Split-levels and walkouts from the 1960s and 1970s put the furnace on a lower level that's often finished around it, and the rooms at the far end of a long floor plan are the first to fall behind when a blower weakens or a filter clogs. The 1950s ramblers near Glen Lake have simpler basements but older flues.
Storms on wooded streets knock the power out, and furnace control boards don't always come back cleanly from a surge or a rough restart. A furnace that shows a code after an outage, runs the inducer and never lights, or won't start at all is a common call. Snow sliding off roofs and drifting on slopes can also bury a side-wall PVC vent. Beyond that, the repairs are the usual ones for furnaces this age: igniters, flame sensors, inducers and pressure switches.
Updated November 10, 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: Won't ignite · Short cycling · Blinking light codes · Pressure switch trips · Signs your furnace needs a technician
Start with the breaker, the service switch near the furnace, and whether the thermostat reset itself to off. If those are fine, the control board or transformer may have taken a surge when the power returned, or the furnace locked out on a failed start. A board with a blown fuse is a common repair. Control boards are among the pricier furnace parts, so we test the board, transformer and fuse before replacing one.
Rarely. In a long, spread-out floor plan, the room farthest from the furnace sits last on the duct system, often with the most outside walls. It loses heat fastest and gets warm air last. We measure the airflow at that register and look for crushed or disconnected ducts, closed dampers and leaks in unheated spaces. Balancing the dampers or adding a return usually does more than a bigger furnace would.
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.
Read the guideWater under your furnace, even in summer? Find the source by where it drips: drain, pump, humidifier or AC coil, and what our $79 trip charge covers.
Read the guideConverting an oil furnace or boiler to natural gas in Minnesota: $6,000–$20,000 nationally, getting gas to the house, venting, the oil tank and hot water.
Read the guideHeat out? AC quit? Call or send a request.