The short answer
When a York furnace won’t turn on in Northern Virginia, check four things first: power to the furnace, the gas valve on the pipe, the on switch on the furnace’s own gas valve, and the blower door, because the furnace has no power at all when that door is off. If those are fine, look at the light through the small window in the lower door. A slow green or amber flash is normal. Rapid red flashes mean the furnace stopped itself, and the number of flashes tells you why. After three failed tries to light, it shuts down for an hour.
Give it a minute first
A York furnace doesn’t light the moment the thermostat clicks. From York’s TM9E install guide: the inducer runs first to clear the heat exchanger, the igniter glows for about 17 seconds, the gas valve opens, and about 30 seconds after the flame lights the blower comes on. York’s user manual says the burners may take 30 to 60 seconds to light. There’s no pilot light on these furnaces, so there’s nothing to relight. If you hear the inducer and it’s been less than a minute, wait.
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The four checks from York’s user manual
- Power. The breaker, and the furnace switch on or near the furnace, which looks like a light switch. The thermostat needs this power too, so a blank thermostat screen often starts here.
- The gas handle. The handle on the gas pipe going into the furnace runs along the pipe when it’s open. Across the pipe is off.
- The switch on the gas valve. Inside the upper door, the furnace’s gas valve has its own on and off switch. It should be on.
- The blower door. Take it off and the furnace has no power at all; York’s install guide says the door switch interrupts all power at the unit. Set it back so it seats flat and presses the switch.
York’s user manual is firm on the rest: owners shouldn’t buy, install or replace furnace parts themselves. That covers sensors, switches and boards.
Read the light
The light sits on the control board, low in the cabinet, and shows through the window in the blower door. Count the red flashes between pauses. These are the ones behind most no-heat calls on York furnaces, from the TM9E and TM9V install guides:
Swipe to see all columns →
Swipe to see all columns →
| Light | What it means |
|---|---|
| Slow green flash | Normal: powered, no call for heat |
| Slow amber flash | Normal: the thermostat is calling and it’s heating |
| 3 red | Pressure switch open when it should be closed: inducer, vent, hose or switch |
| 4 red | Main limit opened: the furnace overheated, filter first |
| 5 red | Rollout switch opened; it resets by hand, and it needs a tech |
| 6 red | Pressure switch opened four times in one call; locks out for an hour |
| 7 red | No flame after three tries; locks out for an hour |
| 8 red | Flame lost five times in one call; locks out for an hour |
| 11 red | Main limit open more than five minutes, usually the blower motor or wheel |
| Steady on, any color | The control board failed |
Two-stage and modulating York furnaces add a few more; every code is in our York furnace codes guide.
Soft lockouts and hard lockouts
York boards lock out two ways. A soft lockout clears itself after an hour: three failed tries to light, the flame dropping out five times in one call, or the main limit tripping five times in one call. A hard lockout waits for someone to turn the power off and on: a rollout switch (5 red), or the main limit staying open for more than five minutes (11 red).
To clear either one: Set the thermostat to off. Turn off the breaker or the switch for the equipment, wait about five minutes, turn it back on and set the thermostat back. Do it once. If the furnace runs and locks out again, the cause is still there.
The usual causes, one at a time
3 or 6 red: the inducer runs, nothing lights
What you notice: A hum from the top of the furnace, no glow, no flame. After a few tries it stops and flashes 3 red, or 6 red once the switch has opened four times in one call.
What causes it: The pressure switch can’t prove the vent is clear. A blocked PVC vent, a clogged condensate drain or trap, a cracked hose or a slow inducer.
What you can do: Clear the white pipes outside by hand. Check the drain beside the furnace and the condensate pump if you have one. Then one power cycle.
When to call us: If it comes back. Our York pressure switch guide has each cause.
7 red: it never lit
What you notice: The igniter glows, no flame, three times. Then the furnace stops for an hour and flashes 7 red.
What causes it: Gas isn’t reaching the burners, or the igniter isn’t getting hot enough to light it. A closed gas handle, the gas valve switch off, or a worn part.
What you can do: Check the gas handle, the switch on the gas valve and your other gas appliances. York’s manual says to call after three failed tries, not to keep trying.
When to call us: If the gas is on and it still won’t light.
8 red: it lights, then goes out
What you notice: The burners light for a few seconds and go out. After five times in one call, it locks out.
What causes it: The flame sensor can’t prove the flame, usually because it’s coated. The board locks out completely once the signal falls under 0.1 microamps.
What you can do: One power cycle. Leave the sensor alone.
When to call us: If it keeps dropping out. More in our York flame sensor guide.
4 or 11 red: it overheats
What you notice: Heat for a while, then the burners shut off while the blower keeps running. 4 red is the limit tripping; 11 red means it stayed open more than five minutes.
What causes it: Not enough air through the furnace. York’s guide lists a dirty filter, a blower that failed and too many closed registers. 11 red is often the blower motor itself.
What you can do: Change the filter and open the vents.
When to call us: If it keeps tripping, or on 11 red. A blower motor or its capacitor is a tech’s job. More in our York blower motor guide.
5 red: the rollout switch
What you notice: No heat, and the board flashes 5 red. It won’t clear on its own.
What causes it: Flame came out of the burner area where it shouldn’t. York’s guide points at the combustion blower, the heat exchanger or a blocked vent.
What you can do: Nothing. The switch resets by hand, and the reason it tripped has to be found first.
When to call us: Right away. Don’t reset it and run it.
Coleman and Luxaire are the same furnace
Coleman and Luxaire furnaces come off the same line as York and use the same boards and the same lights. Everything here applies; the brand guides are Coleman furnace codes and Luxaire furnace codes. Bosch has run the home heating and cooling business behind York since July 31, 2025 (Bosch announcement), using the York name under a long-term license from Johnson Controls.
What the visit looks like
The tech reads the light and the fault history, watches a full start, and checks each step: the vent and drain, the pressure switch readings, the igniter, the gas pressure, the flame signal and the blower. You get the cause and the price before any part goes in. If you smell gas, don’t touch any switches: leave the house and call your gas company from outside.
Any brand: furnace won’t turn on and furnace blinking light. Other brands that won’t light: Lennox and American Standard. A York heat pump instead: York heat pump not heating. Every brand is in our error codes and warning lights guide, and our York repair page has what we fix and what it costs.
Book a York repair
Call (703) 997-9757 or book online. A diagnostic visit is $99, and the tech reads the code, finds the part that set it and gives you the price before any work starts. We answer day or night. Our heating check is $67 per system, through December 31: furnace, heat pump or boiler. If someone already quoted you a new system, our free second opinion looks at it first. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
Why won’t my York furnace turn on?
Check the power and furnace switch, the gas handle, the switch on the furnace’s gas valve and the blower door. If those are right, read the light in the door window: rapid red flashes mean it locked itself out, and the count says why.
How do I reset a York furnace?
Turn off the breaker or furnace switch, wait about five minutes and turn it back on. A soft lockout also clears itself after an hour. If it locks out again, call.
What does 7 red flashes mean on a York furnace?
It tried to light three times and never saw flame, so it shut down for an hour. Check the gas handle and the gas valve switch, then call if it still won’t light.
How long does it take a York furnace to light?
York’s user manual says 30 to 60 seconds. The inducer runs first, then the igniter glows for about 17 seconds before the gas opens.
Does a York furnace have a pilot light?
No. York’s gas furnaces light with a hot surface igniter, so there’s no pilot to relight.
