Searches for furnace repair in Virginia go from about 6,600 a month in September to 18,000 in October and 22,000 in December. Almost all of that is the same story: the first night below 40°F, the thermostat calls for heat, and the furnace does nothing, or clicks and gives up, or runs while blowing cold air. A furnace won’t turn on call is the single most common heating repair we make, and most of the causes can be narrowed down before you pick up the phone.
In this article
Furnace won’t turn on: the seven usual causes
| Symptom | Likely cause | DIY-safe? | Needs a tech? |
|---|---|---|---|
| Nothing happens at all | Thermostat (dead batteries, wrong mode), tripped breaker, or furnace switch off | Check all three | Yes if all are fine |
| Clicks repeatedly, never lights | Failed hot-surface igniter or dirty flame sensor | Visual only | Yes |
| Lights, then shuts off in seconds | Dirty flame sensor, or a pressure switch not proving draft | No | Yes |
| Blower runs, air is cold | Burner locked out on a limit switch; often a clogged filter | Replace the filter | Yes if it repeats |
| Runs 1–2 minutes, off 3, repeat | Overheating on the limit switch: airflow or filter | Replace the filter | Yes |
| Blinking light on the board | Fault code — count the flashes and check the door label | Read the code | Yes |
| Smell of gas | Gas valve or supply problem | Stop — leave and call the gas company | Yes |
Furnace won’t turn on? Safe checks before you call
- Thermostat. Set to HEAT, temperature above room temp, and fresh batteries. Half of the early-season furnace won’t turn on calls end here.
- Power. The furnace has a light-switch-style disconnect on or near it and its own breaker. Both get bumped during summer basement projects.
- Filter. A filter that hasn’t been changed since spring starves the furnace of air and trips the limit switch. Replace it and try again.
- Furnace door. The blower door has a safety switch. If it isn’t fully seated after a filter change, nothing runs.
- Condensate drain (high-efficiency units). A 90%+ furnace won’t fire if its condensate trap is clogged and the float switch is up. Look for standing water in the drain line.
- Fault light. Most furnaces blink a code through a small window in the door. The legend is printed inside the door. Tell the technician the code; it shortens the visit.
- Stop if you smell gas. Don’t operate switches, leave the house, and call Washington Gas or Columbia Gas from outside.
The parts behind most furnace won’t turn on calls
Hot-surface igniters wear out every five to ten years and are the single most replaced furnace part. Flame sensors just get dirty; a technician cleans or replaces them in minutes. Pressure switches fail or their hoses crack. Limit switches trip when airflow is poor and eventually fail. Control boards fail less often but take everything down with them. Every one of these is a same-day part on Carrier, Bryant, Trane, Lennox, Goodman, Rheem, Ruud, York and Coleman furnaces, and every one costs a small fraction of a new furnace.
Why the first cold night is the worst time to learn your furnace won’t turn on
Heating companies book out fast once the first freeze hits. A furnace that gets tested in late September, before the weather turns, gets fixed on a quiet weekday with same-day service. The same furnace in the third week of October waits behind everyone else’s. Run the furnace for ten minutes on the first cool evening; if the furnace won’t turn on or does anything on the table above, call now.
Appliances Pro Inc — rated 4.8★ by 513 Google reviewers, serving Northern Virginia since 2008. Open 7 days, 5 AM–10 PM. Free service call with any completed repair, 90-day parts and labor warranty.
Furnace won’t turn on after a power outage
A share of no-heat calls every fall come the morning after a storm. If the furnace won’t turn on once the power is back, check the breaker first, because a surge trips the furnace circuit more often than any other in the house. Then look at the thermostat: many battery-backed models reset to COOL or OFF when they lose power. If both are fine and the furnace won’t turn on, the control board may have locked out; switching the furnace disconnect off for one full minute and back on clears most lockouts. If it still does nothing, the board or transformer took the surge and it is a technician visit.
When to call because the furnace won’t turn on
- The furnace clicks but never ignites
- It lights and shuts off within seconds
- It runs but blows cold air after a filter change
- The board shows a fault code
- It short-cycles on and off every few minutes
- Any gas smell — after you’ve called the gas company
Call (703) 916-1130 or book online. Same-day service is usually available when you call before noon. Every completed repair includes a FREE service call, and all work carries a 90-day parts and labor warranty.
See our furnace repair page for more detail, and if you’re nearby, our appliance repair in Manassas VA team can usually work you into the schedule quickly. For manufacturer support resources, see carrier.com residential support.
Frequently asked questions
My furnace won’t turn on but clicks: why?
The igniter is trying to light but either it has failed, the flame sensor is too dirty to confirm a flame, or the pressure switch isn’t proving the draft blower is running. All three are quick, inexpensive repairs. Repeated clicking with no ignition is the most common furnace call we take.
Why is my furnace blowing cold air?
The burners have shut off on a safety limit while the blower keeps running to cool the heat exchanger. A clogged filter is the usual cause. Replace it; if the furnace still cycles cold, the limit switch or flame sensor needs service.
Is it worth repairing an old furnace?
For igniters, sensors, switches, capacitors and blower motors, yes, at any age. The exception is a cracked heat exchanger on a furnace past 15–20 years; that’s a replacement, and we’ll show you the crack rather than ask you to take our word for it.
How soon can you fix a furnace in Northern Virginia?
Same day in most cases when you call before noon, 7 days a week from 5 AM to 10 PM. Our technicians carry common igniters, flame sensors, switches and capacitors for major brands.