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.
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For furnace repair in Roseville, the visit starts with a $79 trip charge, waived when you approve the repair, and a flat-rate price in writing before anything starts. Techs cover Roseville 7am–9pm, seven days. The city's 1950s ramblers often vent furnace and water heater into one chimney, so draft gets tested.
The typical Roseville furnace sits in a 1950s rambler or story-and-a-half, at the end of a basement that has since been finished, behind a door in a room just big enough for the furnace, water heater and softener. That setup causes a specific set of problems. An 80% furnace walled into a small room can run short of combustion air, which shows up as lazy flames, rollout trips or a water heater that spills at its draft hood. The shared masonry chimney has had seventy years to deteriorate, and a partly blocked flue affects both appliances.
The ductwork is original trunk-and-branch, with dampers now hidden above finished ceilings, so rooms at the far end of the trunk run cool and owners blame the furnace. Most furnaces here are second or third replacements, so failures are the ordinary ones: igniters, flame sensors, inducers and blower motors. Xcel Energy supplies the gas citywide.
Updated September 23, 2026
Every furnace repair call in Roseville starts with a $79 trip charge, waived when you approve the repair, and a written price before any work. Same prices in Roseville as in every town we serve. National averages (HomeGuide, 2026), not our prices: a pressure switch $150–$400, a limit switch $100–$375, a control board $300–$650. More in the furnace repair cost guide. For what drives a quote locally, see HVAC cost in Roseville.

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
Possibly. Scorching at the water heater's draft hood means flue gas is spilling out instead of rising up the chimney. In Roseville ramblers the two appliances usually share a flue, so a blocked or deteriorated chimney, a starved furnace room or a furnace inducer pushing into a shared vent can all cause it. It's a carbon monoxide risk. Check your CO alarms, and have us test draft with the furnace and water heater both running.
Usually the ductwork. In a 1950s trunk-and-branch system, the last branches off the trunk get the least air, and leaky joints along the way lose more. Balancing dampers on the branches are often buried above a finished basement ceiling, sometimes left half closed. We measure airflow at the registers and static pressure at the furnace, then adjust dampers, seal joints we can reach or suggest a return for that room.
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