Furnace tune-up and maintenance: checklist and cost

The details vary by company, and a thorough furnace inspection covers these points:

• Combustion. Burners inspected and cleaned, ignitor tested, flame sensor cleaned and its signal measured, gas pressure checked.
• Heat exchanger. Inspected for cracks, rust and soot.
• Venting. Flue or PVC vent pipes checked for blockage, corrosion, slope and secure joints.
• Safety controls. Limit switch, rollout switches and pressure switch tested.
• Airflow. Filter checked, blower wheel and motor inspected, capacitor tested, temperature rise measured against the rating plate.
• Condensate. Trap and drain line cleaned on high-efficiency furnaces.
• Electrical. Connections tightened, wiring checked for heat damage, voltage and current measured.
• Controls. Thermostat operation and a full start-up and shutdown cycle observed.
• Carbon monoxide. A combustion or CO test at the furnace.

• Change the filter on the schedule printed on its packaging, and sooner if it looks gray.
• Keep supply registers and return grilles open and uncovered.
• Keep the area around the furnace clear. Store paint, solvents and anything flammable somewhere else.
• Keep the outdoor intake and exhaust pipes of a high-efficiency furnace free of snow, leaves and nests.
• Test carbon monoxide alarms and replace them when the manufacturer says to.
• Run the heat briefly before the first cold night so problems show up while appointments are easy to get.

The furnace repair guide covers what to check if something does go wrong.

A tune-up is priced as a flat visit. The price moves with your region, the season, the type of furnace and how thorough the visit is. A high-efficiency furnace has more to clean and test than a standard one. Early-fall and off-season appointments are often cheaper than the first cold week, when every company is busy.

Very cheap tune-up offers exist to get a technician into your home, and some of those visits turn into a sales call. Price alone tells you little. Compare what is on the checklist and whether readings are reported.

It pays off when you would book the visits anyway and the terms are clear.

A real visit takes time, involves tools and ends with numbers. Ask for a written report that lists the temperature rise, the flame sensor reading, gas pressure and the combustion or carbon monoxide test result. If a repair is recommended, ask to see the part and the reading that failed.

Be wary of a visit that takes only a few minutes, a technician who never removes a panel, or an urgent recommendation to replace the furnace with no evidence shown. A second opinion is reasonable for any large recommendation.

The CDC advises having your heating system serviced every year by a qualified technician as a way to prevent carbon monoxide poisoning. A yearly visit also catches a weak ignitor, a fouled flame sensor or a blocked drain before it becomes a no-heat call in January. Many manufacturer warranties expect regular maintenance too, so keep your service records.