Our office is on Lafayette Center Drive in Chantilly, which makes this the shortest drive we make and the town where we can most often get somebody out the same day in January. That is worth knowing when it is 18 degrees and the furnace will not light.
Chantilly is gas furnace country. We essentially never see a boiler here, which simplifies the diagnosis considerably: when the heat stops, it is one of about six things.
Two Chantillys, ten years apart
20151, the older side toward Route 50 and Westfields. Houses and townhouses from the 1980s and 1990s, mostly on their second furnace by now, with the original ductwork still doing the distributing. Builder-grade one inch filter slots, one large return, and a bonus room over the garage that has never been warm.
20152, the South Riding side. Later construction, larger houses, frequently two systems, and a good share still on their original equipment. Those furnaces are now in the fifteen to twenty five year band where parts start asking for attention.
Six things that stop a Chantilly furnace
It lights, runs a few seconds, shuts off, then tries again. Flame sensor. A film of oxide on the rod stops it confirming the flame, so the board closes the gas as a safety. Cleaning it runs $95 to $180 and takes ten minutes. This is the most common no-heat call we run, here and everywhere.
Clicking, but no flame. Hot surface igniter. A ceramic element that glows to light the gas and gets brittle with age. $240 to $410 installed, and a normal wear item rather than a sign the furnace is finished.
It runs ten or fifteen minutes, shuts down, comes back later. Overheating, and the furnace is protecting itself. Airflow is the cause: the filter first, then the blower wheel, which collects a felt of dust that strangles it. Pulling and cleaning the wheel is $300 to $440.
Nothing happens at all. Thermostat batteries, the switch that looks like a light switch beside the furnace, then the breaker. If it has power and a call for heat and still does nothing, it is the control board at $550 to $1,180, or a clogged condensate trap at $175 to $420 on a high efficiency unit refusing to fire on purpose.
A whine or rattle before the burners light. The inducer motor, which clears the flue before ignition. When it fails, the furnace will not light at all because a pressure switch is waiting on it. About $1,950.
A squeal or grind while the fan runs. Blower motor on its way out, $670 to $2,400 depending on standard or variable speed. If it still runs, deal with it now rather than after it seizes in a cold snap.
Estimated Costs for Professional Furnace Repair
- Diagnostic visit: about $99.
- Flame sensor cleaned $95 to $180; igniter or sensor replaced $240 to $410.
- Condensate drain or trap: $175 to $420.
- Thermostat: $300 to $640.
- Blower wheel cleaned: $300 to $440. Blower motor: $670 to $2,400.
- Control board: $550 to $1,180. Inducer motor: about $1,950.
- Cracked heat exchanger: not a repair at any price. Here is how to know the diagnosis is real.
Members on our Family Care Plan take 15 percent off every one of those, plus the fall tune-up that finds a weak igniter in October instead of January.
When it is time to replace
ASHRAE puts a gas furnace’s median service life at eighteen years, and ENERGY STAR’s line for even considering replacement is fifteen. Ours: past fifteen, if the repair is more than a third of a replacement, replace it. Under ten, repair almost every time.
A furnace alone runs $4,498 to $12,300 installed. A furnace and air conditioner together run $8,898 to $23,000 depending on system size. If the air conditioner is the same age as the furnace, which in a 20152 house it almost always is, replacing both at once costs less than two separate jobs two years apart.
Washington Gas is paying $500 on a furnace at 95.1 to 96.9 percent efficiency, $700 at 97 percent and up, and $100 on a smart thermostat, when a contractor in its network does the work and files the paperwork. The federal tax credit is gone for anything placed in service after December 31, 2025.
The furnace and AC estimator shows the installed range for your system size in about two minutes, no phone number required. What moves that number is here.
Do this in October
Run the heat for an hour and stand near the furnace for the first two minutes. Inducer, igniter, burners, blower, in that order, no hesitation. Anything that stalls in that sequence is worth a call while the schedule is still open.
Change the filter, and if yours is the one inch builder slot, ask about a proper media cabinet. It is a modest add that solves a lot of the airflow complaints in these houses.
Put a carbon monoxide alarm on each sleeping floor. Virginia requires them in new construction with fuel burning appliances, so most Chantilly houses have them, but the ones from the earliest build years are well past their ten year service life.
SwiftPro is based in Chantilly and works across Northern Virginia. Call (703) 997-9757, book online, or start at the Fairfax County heating repair page. No heat right now is what the 24 hour line is for.
