Furnace Repair Services
Reviewed 2026-07-30
Furnace repair finds and fixes heating problems such as no heat, cold air from vents, short cycling, and ignition failures. It also corrects unsafe combustion so the furnace runs safely again.
Symptoms furnace repair solves
- The furnace blows cold or lukewarm air instead of heat
- The furnace short cycles, turning on and off repeatedly
- No heat at all, even though the thermostat calls for it
- A carbon monoxide detector near the furnace has alarmed
- Unusual smells: burning dust at first startup is normal, but a persistent gas or scorched-metal smell is not
- Loud banging, screeching, or rattling when the furnace starts or runs
- The pilot light or ignitor won't stay lit
When to book furnace repair
- Every fall before heating season begins, per manufacturer and ENERGY STAR maintenance recommendations
- Immediately if a CO detector alarms or you smell gas — evacuate first, then call
- As soon as heat output drops or cycling becomes irregular
- When the furnace is 15+ years old, since failure risk and repair cost both climb
What happens during furnace repair
- Technician checks the thermostat, filter, and basic airflow before opening the unit
- Ignition system (pilot, hot surface ignitor, or spark ignitor) is tested along with the flame sensor
- Heat exchanger is inspected for cracks, which can leak combustion gases including carbon monoxide into supply air
- Gas pressure and burner flame pattern are checked against manufacturer specs
- Blower motor, belt, and electrical components are tested for correct operation
- Technician completes the repair and verifies safe operation with a combustion analyzer or CO meter before leaving
Furnace Repair methods and approaches
Ignition and flame sensor diagnostics
Testing the hot surface ignitor or pilot assembly and cleaning/replacing the flame sensor, the most common cause of a furnace that won't stay lit.
Heat exchanger inspection
Visual and sometimes camera inspection for cracks, which per CPSC and NFPA guidance is a safety-critical check since a cracked exchanger can introduce CO into breathing air.
Combustion analysis
A combustion analyzer measures CO, CO2, and O2 levels in flue gas to confirm the burner is combusting properly and venting safely, per NFPA 54 fuel gas code guidance.
What drives furnace repair pricing
- Which component failed (ignitor, flame sensor, blower motor, heat exchanger)
- Fuel type — gas, electric, oil, or propane repairs differ in parts and labor
- Age of the unit and part availability
- Whether ductwork or venting issues are contributing to the symptom
- Emergency/after-hours service premiums
- Whether a heat exchanger replacement is possible or the whole unit needs replacing
Questions to ask your hvac technician
- What is your diagnostic fee, and does it apply to the repair cost?
- Did you test the heat exchanger for cracks, and how?
- What CO reading did you get on the combustion analyzer?
- Is this repair covered under any existing manufacturer warranty?
- Given the furnace's age, would you recommend repair or replacement?
- Are you licensed for gas appliance work in this state?
Furnace Repair safety and licensing
- If a CO detector alarms, leave the house immediately, call 911 or the gas company, and do not re-enter until cleared — carbon monoxide is odorless and can be fatal.
- Never attempt to repair gas connections, ignition systems, or heat exchangers yourself; this is licensed technician work under NFPA 54.
- Replace CO detector batteries and test units twice a year — CPSC data shows unpowered or expired detectors are a leading factor in CO poisoning deaths.
Furnace Repair questions homeowners ask
How much does furnace repair cost?
Common repairs like an ignitor or flame sensor run $150-$400; a blower motor replacement runs $400-$900, and heat exchanger replacement can run $1,000-$2,500 or point toward full replacement.
Is it safe to run a furnace with a cracked heat exchanger?
No. A cracked heat exchanger can allow carbon monoxide into the supply air stream, and most technicians will red-tag the unit and shut it down immediately until repaired.
Why does my furnace blow cold air before heating?
A brief burst of room-temperature air during startup is normal while the heat exchanger warms up. Continuous cold air suggests an ignition failure or the blower running without a flame.
Problems that lead to furnace repair
- Why Is My House So Cold?
- Why Is My House Getting a Furnace That Blows Cold Air?
- Why Is My House Getting High Energy Bills?
- Why Is My House Making Creaking Noises at Night?
Sources for this furnace repair guide
- National Fire Protection Association, NFPA 54 National Fuel Gas Code
- U.S. Consumer Product Safety Commission carbon monoxide safety data
- ENERGY STAR furnace maintenance guidance