Cracked Heat Exchanger: Symptoms, How It's Confirmed and What to Ask For
Signs of a cracked furnace heat exchanger, how a technician confirms one, what to ask for if your furnace is red-tagged, and when to repair or replace it.
Read the guide
Mendota Heights homeowners can reach us 7am–9pm every day for furnace repair, with a written flat-rate price before work and the $79 trip charge waived once you approve the repair. Xcel Energy delivers the gas citywide, and the houses run from 1950s builds to 1990s subdivisions.
Furnace calls in Mendota Heights follow the building decades. About 850 houses went up in the 1940s and 50s, and those that still run an 80% furnace vent it through a masonry chimney, where draft problems and worn inducers show up. The 1980s and 90s houses, the city's biggest wave, mostly have condensing furnaces by now, vented in PVC, and those fail in their own ways: a condensate trap clogged with sludge, a pressure switch hose split or full of water, an inducer that howls at startup, a flame sensor coated with residue.
Lot size shapes a few calls too. On large wooded lots the PVC intake can pull in leaves or sit buried under snow on the far side of the house, and a blocked pipe shuts the furnace down. In houses tightened by the airport sound insulation program, we confirm that any older atmospheric appliance still gets enough combustion air.
Updated September 26, 2026
Every furnace repair call in Mendota Heights starts with a $79 trip charge, waived when you approve the repair, and a written price before any work. Same prices in Mendota Heights as in every town we serve. National averages (HomeGuide, 2026), not our prices: a PSC blower motor $500–$1,400, a variable-speed (ECM) blower motor $800–$2,300, an igniter $100–$250. More in the furnace repair cost guide.

More detail on our furnace repair page.
Symptom guides: Blowing cold air · Won't ignite · Short cycling · Blinking light codes · Pressure switch trips · Strange noises · Leaking water · Burning smell · Red tag · Carbon monoxide
The pressure switch confirms the inducer is moving exhaust, and it opens when something restricts that flow. Check the PVC pipes outside first: leaves, a wasp nest or packed snow is the easiest fix. Inside, water trapped in the switch hose, a clogged condensate trap or a weak inducer causes the same code, and sometimes the switch itself fails. We test it with a manometer before replacing anything.
Wind across the chimney top can push exhaust back down, and the furnace's pressure switch or a spill switch shuts the burners off to protect you. A missing or damaged chimney cap, a flue too short for the roofline, or trees grown up around the chimney make it worse. We measure draft and CO at the furnace and water heater, and a cap, a liner or a sealed-combustion furnace solves it.
Signs of a cracked furnace heat exchanger, how a technician confirms one, what to ask for if your furnace is red-tagged, and when to repair or replace it.
Read the guideKeep the boiler or switch to a furnace? How Saint Paul radiator homes and postwar houses decide, what each costs to replace, and how to add AC without ducts.
Read the guideThe blinking light on a furnace is a fault code from the control board. How to read it safely, what common codes mean, and when a reset is fine or not.
Read the guideFurnace repair in Mendota Heights? Call or send a request.