Furnace Repair Cost in 2026

The two cheapest fixes are the two most common causes of "furnace won't stay on"

A flame sensor detects whether the burner has actually ignited; if it's dirty or failing, the furnace's control board reads it as "no flame" and shuts the gas valve as a safety measure, even though the burner lit fine: producing a furnace that fires briefly, then shuts off, over and over. An igniter that's cracked or weakening causes a similar symptom from the opposite direction: it fails to light the burner at all, or lights it unreliably. Together these two parts account for a large share of "furnace won't stay running" service calls, and both are inexpensive, fast repairs, which is exactly why a technician should check them before quoting anything more expensive for the same symptom.

Blower motor problems

The blower motor pushes heated air through the ductwork, and it's one of the harder-working mechanical parts in the system, it runs every time the furnace calls for heat, for the entire heating season, in a cold-climate market like Duluth, MN, that can mean months of near-continuous cycling. A failing motor often shows up as weak airflow, unusual noise, or the furnace overheating and shutting down on its high-limit safety switch because air isn't moving fast enough across the heat exchanger. A repair (bearing, capacitor, or motor cleaning) runs $150–$900; if the motor itself has failed, full replacement can run up to $2,000 depending on motor type: variable-speed ECM motors cost significantly more than older single-speed motors.

Heat exchanger: the one repair that's also a safety call

The heat exchanger separates the combustion gases (including carbon monoxide) from the air that actually circulates through your home: it transfers heat across that barrier without letting the two air streams mix. A cracked heat exchanger breaks that separation, and it is treated as a genuine safety issue, not just a performance problem: the Consumer Product Safety Commission warns carbon monoxide from heating equipment is an "invisible killer" precisely because it's odorless and colorless: most technicians will red-tag a furnace with a confirmed cracked heat exchanger and shut off the gas until it's replaced or the furnace itself is replaced. Replacement alone runs $1,000–$3,000; given a cracked heat exchanger usually shows up on an older furnace already near the end of its life, it's one of the most common points where "repair or replace the whole furnace" becomes a real, immediate decision rather than a someday question.

What's safe to check yourself, and what isn't

A dirty air filter restricting airflow, a thermostat with dead batteries or a wrong setting, or a closed supply/return vent are all things a homeowner can check and fix before calling anyone, and they genuinely do cause a meaningful share of "furnace isn't working" calls. Anything involving the gas valve, the burner assembly, the heat exchanger, or the electrical control board should go to a licensed technician: these involve combustion safety, carbon monoxide risk, or line-voltage electrical work, none of which are reasonable DIY territory regardless of how simple a YouTube video makes it look.