Open 24/7 for emergencies
A Lennox furnace or AC repair in Northern Virginia starts with the $99 diagnostic, and most Lennox furnace, AC and heat pump repairs run $95 to $1,500, priced in writing before anything is touched. Every Lennox line, from a Merit ML180 to a Signature SLP99V on iComfort, is the same work to us.
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Licensed and insuredVirginia Class A contractor #2705192276
24/7 emergency serviceOften same-day, and we will tell you honestly when we can get there.
Our own HVAC installersA dedicated heating and cooling team, separate from our plumbers
Price in writing firstYou see every option priced before anything is ordered
Read your own Lennox
The things people describe on the phone, what they turn out to be on a Lennox, and what the fix costs.
The burners lit and went out, or never lit. On a Lennox that’s usually a sooted flame sensor ($95 to $180 to clean) or a cracked igniter ($240 to $410). The board’s light will be flashing a code; the table below says which. On a Lennox with a two-digit display, it’s printing the code instead of flashing it.
A furnace that keeps restarting is protecting itself: a dirty flame sensor, a clogged filter tripping the high limit, or a pressure switch that can’t prove the venting. Start with the filter. Then count the flashes.
Most of the time it’s the run capacitor ($240 to $370). Turn it off at the thermostat: a compressor that keeps trying to start against a dead capacitor can burn itself out.
In summer, ice means the coil isn’t getting enough air (a filter, a dirty blower wheel at $300 to $440) or it’s low on refrigerant, which means a leak. On a heat pump in winter, some frost is normal; a solid block of ice that never clears points at the defrost board ($450 to $1,150).
A high-efficiency furnace and every AC coil make water, and it has to drain. A clogged trap or drain line ($175 to $420 to clear, with a float switch added) is the usual answer. Water from the tank beside it is a water heater call.
A squeal or whine is usually the inducer or the blower motor’s bearings on the way out (a blower motor runs $670 to $2,400, standard against variable speed). A bang at startup is delayed ignition: gas building up before it lights. That one needs a look soon, not next month.
A system that never shuts off is short on capacity: low refrigerant, a dirty outdoor coil, a blower wheel packed with dust, or a heat pump leaning on its backup electric heat. Each one is a price, not a guess.
Leave the house, then call the gas company from outside. Once it’s safe, call us: (703) 997-9757, 24/7.
The codes on the board
Open the furnace’s lower door (gas off first if you smell anything) and look through the little window at the control board. Write the code down before you reset anything: a reset clears it.
These furnaces print an E and three digits on the board. An S30 or S40 thermostat shows the same number as an alert.
| Code | What it means | What it usually takes |
|---|---|---|
| E200 | Hard lockout: the flame rollout circuit opened | Call. Rollout means heat or flame where it shouldn’t be |
| E207 | Hot surface igniter sensed open | A new igniter |
| E223 | Low pressure switch failed open | The venting, the inducer or the pressure switch |
| E240 | Low flame current | Usually a flame sensor cleaning |
| E241 | Flame sensed out of sequence | Shut the gas off and call |
| E250 | Limit switch circuit open | Start with the filter: the furnace is overheating |
| E270 | Soft lockout: no flame after the maximum retries | Gas supply, igniter or flame sensor |
| E292 | Blower motor can’t start | A blocked wheel or a seized blower motor |
| E311 | Heat cut back to match the blower’s airflow | Check the filter and the ducts |
| E150 | Refrigerant leak alarm (K models) | A leak at or in the indoor coil |
Source: Lennox SL280UHVK installation instructions. Codes vary by model and control board: the chart printed on your unit, or its manual, is the final word.
Count the red flashes on the board through the window in the lower door.
| Flashes | What it means | What it usually takes |
|---|---|---|
| 3 | Burner failed to light, or lost flame | Gas supply, igniter or flame sensor |
| 4 | Low flame signal | A flame sensor cleaning |
| 5 | Watchguard: too many failed tries | The igniter, flame sensor or gas valve |
| 7 | A limit stayed open longer than 3 minutes | Airflow: the filter, blower or a closed vent |
| 8 | Rollout switch open | Call: a rollout trip needs a look at the burners and venting |
| 9 | Pressure switch failed to close | The venting, the inducer or the switch |
| 12 | Flame sensed with the gas valve off | Call |
Source: Lennox ML180UHE unit information. Codes vary by model and control board: the chart printed on your unit, or its manual, is the final word.
| Code | What it means | What it usually takes |
|---|---|---|
| 180 | Outdoor temperature sensor problem | A sensor |
| 400 | Compressor internal overload tripped | Often a dirty coil or a weak capacitor |
| 401 | Compressor ran over 18 hours, or refrigerant pressure is low | A leak to find |
| 403 | Compressor short-cycling | The thermostat setup, refrigerant or airflow |
| 404 | Compressor rotor locked | A capacitor, or a compressor that’s seized |
| 410 | Low pressure switch open | Low refrigerant or low airflow |
| 412 | High pressure switch open | A dirty outdoor coil or a dead outdoor fan |
| 414 | Discharge line too hot | Low refrigerant, usually |
Source: Lennox communicating systems alert code guide. Codes vary by model and control board: the chart printed on your unit, or its manual, is the final word.
What it costs
Our own repair prices, the same on a Lennox as on anything else. Tap a system to narrow the list.
Flame sensor cleaned
The thin rod that proves the burners lit. Coated in soot, it tells the board the flame went out, and the gas shuts off a few seconds after the burners light.
$95 to $180
Condensate drain cleared, trap and switch added
High-efficiency furnaces and every AC coil make water. When the drain or trap clogs, a float switch stops the system on purpose so the water doesn’t end up in the ceiling.
$175 to $420
Refrigerant topped up
One to three pounds. If it needs it again next season it’s leaking, and topping it up every year is the expensive way to lose.
$190 to $740
Run capacitor replaced
The part that kicks the compressor and fan motors into turning. The single most common reason an outdoor unit hums and never starts.
$240 to $370
Igniter or flame sensor replaced
A cracked hot surface igniter glows weakly or not at all, so the burners never light. Usually on the van.
$240 to $410
Contactor replaced
The relay that sends power to the outdoor unit. Burnt or stuck points mean it sits silent while the thermostat calls, or runs when it shouldn’t.
$290 to $425
Blower wheel pulled and cleaned
A wheel caked in dust moves a fraction of the air it should: weak airflow, a frozen coil, a furnace tripping its limit.
$300 to $440
Thermostat replaced
Standard through smart, wired and set up for the system it runs.
$300 to $640
Defrost board replaced
Heat pumps only: the board that decides when to melt the ice off the outdoor coil.
$450 to $1,150
Control board replaced
The brain in the furnace or air handler. When it goes, nothing downstream of it does what it’s told.
$550 to $1,180
Blower motor replaced
The indoor fan motor. The spread is a standard motor against a variable-speed one.
$670 to $2,400
Condenser fan motor replaced
The fan on top of the outdoor unit. If it stops while the compressor runs, the repair gets more expensive by the minute.
$1,100 to $1,500
Refrigerant leak found and repaired
Finding it, fixing it, then recharging the system.
$1,850 to $2,700
or $31/mo at 0% APR for 60 months
Compressor replaced, part under warranty
Labor and refrigerant, when the manufacturer still covers the compressor.
$1,900 to $2,500
or $32/mo at 0% APR for 60 months
Compressor replaced, out of warranty
The big one, and usually the point where replacing the system wins. You get both numbers.
$2,200 to $5,100
or $37/mo at 0% APR for 60 months
Monthly figures: 60mo @ 0% APR on each starting price, the whole price financed, on approved credit. Longer plans lower the payment and cost more in total. The lender sets the final terms. How financing works
Lennox parts aren’t a problem. Lennox’s own stores sell to licensed contractors, and common Lennox furnace parts, like the ignition control on a Merit furnace, have universal replacements. Comfort+ members get the $99 diagnostic included in the visit, 15% off any service, and 50% of each repair bill banked toward replacing that system, up to $1,500. How Comfort+ works.
Fix it or replace it
The serial number on the rating plate gives the year. Here’s how to read it.
A Lennox serial number has 10 characters. On units built since 1973, the 3rd and 4th are the year: 5899L17212 was built in 1999, 1606B13871 in 2006. Lennox doesn’t publish this key itself; it comes from home inspection references, so read it as a good guide.
A gas furnace usually lasts 15 to 20 years with yearly maintenance (how long a furnace lasts), an outdoor unit a bit less.
Gas furnace alone
$4,285 to $14,040
or $71/mo at 0% APR for 60 months
Keeping the AC you have. By size and efficiency, installed.
Furnace and AC together
$8,898 to $23,000
or $148/mo at 0% APR for 60 months
2 to 5 ton, matched, installed with the permit.
Heat pump system
$8,499 to $21,650
or $142/mo at 0% APR for 60 months
Heat pump and air handler, 2 to 5 ton, installed.
Monthly figures: 60mo @ 0% APR on each starting price, the whole price financed, on approved credit. Longer plans lower the payment and cost more in total. The lender sets the final terms. How financing works
Want your own number before anyone comes out? The HVAC estimator prices your house in a few questions.
A Lennox gas furnace on one of our repair calls in a Northern Virginia basement.
When your Lennox is done
Lennox makes good equipment. When one is past fixing, here’s why the system we put in its place is a Trane.
Holding a Lennox replacement quote? Our free second opinion looks at the system and the quote, and puts a Trane priced in writing beside it. Several Northern Virginia companies that sell Lennox have been bought by investor groups since 2022. Curious about the one that quoted you? Who owns which HVAC company, with the sale dates.
A Trane outdoor unit one of our installers just set. Trane is our first pick when a system is done.
The system we put in first
Built to take a beating. Put in by our crew.
Heat lamps, snow and rain on one outdoor unit: that’s Trane’s own film. We’re a Trane Comfort Specialist, on Trane’s own dealer locator, and when you pick a Trane, our crew puts it in.
Films: Trane’s own.
The warranty
Maybe, and the serial number tells us. Here’s how Lennox’s warranty works.
Lennox’s own terms: Lennox’s warranty page.
Where we work
Out of Chantilly and Ashburn, across six counties. Pick your town for its own furnace repair page: the houses there, the county’s permit rules, and the same prices.
Keep reading
Every make we work on, in one place: the brands we repair.
Asked on the phone
The diagnostic is $99. Most Lennox repairs run $95 to $1,500: a flame sensor cleaned is $95 to $180, an igniter $240 to $410, a capacitor $240 to $370, a control board $550 to $1,180. If it’s past fixing, a new furnace we install is $4,285 to $14,040 and a furnace with an AC is $8,898 to $23,000. From about $71 a month at 0% APR for 60 months, the whole price financed, on approved credit. How financing works
Yes: Merit, Elite and the Dave Lennox Signature Collection, gas or propane, iComfort systems included. A Lennox lights, proves its flame and moves air the way any furnace does, and the codes on its board are printed in Lennox’s own manuals, which is where the tables on this page come from.
Call us. Your Lennox doesn’t care who installed it. We find the fault, price it in writing and fix it. If a covered part is the answer, we’ll tell you which part failed, whether it’s covered, and how Lennox’s claim process works. Several Northern Virginia companies that sell Lennox have been bought by investor groups since 2022; who owns which HVAC company lists the sales.
On a Merit furnace the red light is a code: count the flashes. 3 means the burner didn’t light or lost its flame, 4 is a weak flame signal (usually the flame sensor), 7 is a limit open too long (usually airflow), 8 is the rollout switch and 9 the pressure switch. A Signature or Elite furnace prints an E-code instead; both tables are on this page.
On most Lennox equipment, yes, though Lennox says you lose some features and recommends its own thermostat (Lennox FAQ). On the top SL25KCV air conditioner and SL22KLV heat pump, no: Lennox says they only run with a Lennox communicating thermostat.
Yes. Lennox builds solid furnaces, air conditioners and heat pumps; Consumer Reports rated it Excellent for owner satisfaction in its 2018 and 2020 central air surveys, and its top Signature furnace is rated up to 99% AFUE. We’d still put in a Trane: about the same price, and a warranty claim we can file ourselves.
About as long as any gas furnace, usually 15 to 20 years with yearly maintenance. Our guide to how long a furnace lasts goes through what shortens it.
Get the Lennox running
No heat or no cooling, call: (703) 997-9757, 24/7. Not that urgent? Send the form at the top and the office calls or texts you back to set a time.
SwiftPro Heating, Cooling & Plumbing
4230 Lafayette Center Dr N, Chantilly, VA 20151
44679 Endicott Dr, Suite 211, Ashburn, VA 20147
Virginia Class A contractor license #2705192276
Repair prices are SwiftPro’s own, by part, in Northern Virginia; yours is quoted in writing after the diagnostic. Replacement prices are our installed ranges by system size.
Lennox, Merit, Elite, Dave Lennox Signature Collection and iComfort are trademarks of Lennox International Inc.