Heating repair: what to know

What the job involves, what changes the price, and what to ask a pro.

What heating repair is

Heating repair diagnoses and fixes a furnace, boiler or heat pump that will not start, blows cold air, cycles on and off or makes noise. People usually call when the house stops getting warm during a cold snap.

Signs you need it

  • The blower runs but the air from the registers stays cold.
  • The burners light and then shut off within a minute or two.
  • The system runs nonstop and some rooms never reach the set temperature.
  • A boiler pressure gauge drops below its normal range, or the boiler knocks, gurgles or stops heating radiators.
  • A carbon monoxide alarm goes off, or you smell gas or see a yellow, flickering burner flame. Leave the house first, then call the gas utility from outside.
  • The furnace squeals, rattles or bangs when it starts.

What the pro does

  • Check the thermostat settings and wiring, the furnace switch and breaker, and read the fault code on the control board.
  • Test the ignitor or pilot, the flame sensor and the gas valve signal, and measure flame current with a meter.
  • Check the blower motor, capacitor, limit switch and airflow at the filter and registers.
  • Run a combustion analyzer at the flue to check for carbon monoxide and look for cracks or soot that point to a failing heat exchanger.
  • Replace the failed part, such as a flame sensor, control board, igniter, pump or valve, and confirm the cause is fixed.
  • Run the system through a full heating cycle to confirm it heats, reaches temperature and shuts off on its own.

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Which part failed. A flame sensor or control board is a smaller job than a blower motor or a heat exchanger.
  • Fuel type. Gas, oil, electric and heat pump systems use different parts and different safety checks.
  • Age and parts availability for the model. Older units can need parts that take time to source.
  • Access to the unit, such as a tight attic, a crawl space or a basement packed with stored items.
  • Whether the repair involves refrigerant, which is the case with heat pumps and commonly requires a refrigerant handling certification.
  • Whether the system needs gas line or venting fixes before the repair can be finished.
  • Repair versus replacement when the unit is old and several parts have failed.

What a written quote should spell out

  • The diagnosed fault and the reason the part failed, not only the part that was replaced.
  • Each part listed by model number, and whether it is new, refurbished or used.
  • Whether the combustion test and carbon monoxide reading are included, and the readings you will record.
  • Any venting, gas or electrical fix needed for the repair to be safe, listed as a separate line.
  • Warranty terms on the part and on the labor.

Questions to ask before you hire

  • Did you find the cause of the failure, or are you only replacing the part that failed last?
  • Will you run a carbon monoxide test and check the heat exchanger before you close the unit?
  • Are the parts you plan to use available for my model, and how long will they take if they are not on the truck?
  • Will the repair include cleaning the burners and the flame sensor, or only replacing parts?
  • If the unit is older, what would make you recommend replacing it instead of repairing it?
  • Does your labor warranty cover the same fault if it returns?
  • Are you licensed for this work where I live, and can you show proof before the visit?

Red flags

  • The pro says the furnace is dead and must be replaced without testing the ignition, controls or heat exchanger.
  • The pro wants to swap a control board or sensor without checking the wiring or what caused the fault.
  • The pro will not show the combustion readings or the failed part.
  • The estimate is verbal only, with no written list of parts and labor.

What you can do yourself

You can check the thermostat batteries and settings, replace a clogged filter, and clear snow or debris from around the outdoor unit or exhaust vent. Leave the burners, gas valve, control board and heat exchanger to a licensed technician. If you smell gas or a carbon monoxide alarm goes off, leave the house and call the gas utility from outside.

Licenses and permits

Heating repair is commonly done by licensed HVAC contractors, and gas or electrical work may need a licensed trade. Check with your state or local licensing agency to confirm what your repair requires.

Heating repair questions

How do I tell if the problem is the furnace or the thermostat?

Set the thermostat to heat, a few degrees above the room temperature, and listen for the furnace to start. If nothing starts, the thermostat or its wiring may be the cause. If the furnace starts and then shuts down or the house stays cold, the fault is more likely in the furnace or the airflow.

Is it worth repairing an older furnace?

It depends on what fails. A single inexpensive part on a sound unit is usually worth fixing. Repeated failures across several components, a cracked heat exchanger or parts that are hard to find usually make replacement the better choice.

Why does my furnace turn on and off every few minutes?

Short cycling can come from a dirty filter that overheats the unit, a dirty flame sensor, a blocked exhaust, or a limit switch that trips because airflow is poor. A technician should find the cause before the heat exchanger is stressed.

Can I run a space heater until the repair?

Use one plugged directly into a wall outlet, not an extension cord, with clear space from furniture and curtains. Turn it off when you leave the room.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

Edit history

How it works

  1. 1. Describe the job

    Pick the service, add your ZIP and a sentence about what is going on.

  2. 2. Pick the pros you want

    See screened pros who serve your ZIP and choose who you want to hear from.

  3. 3. They reach out

    They contact you the way you chose: phone, email or in-app messages.

More heating and cooling guides

Find a pro near you

Find a pro

About this guide

Request heating repair