Furnace inducer runs but burners never light

The small blower at the top of the furnace spins up and keeps running, but the igniter never glows and the burners never light. The furnace is waiting for a signal that never comes.

Some of the faults listed here are gas-safety faults. Those ones involve the gas valve, the burner compartment, or the heat exchanger — the parts whose failure can put combustion products, including carbon monoxide, into the air the house breathes, and each carries this warning on its own page. Do not keep resetting a furnace that reports one of them in order to hold the heat on. Have it looked at by a licensed technician, and make sure there is a working carbon monoxide alarm on every level of the home, including the level the furnace is on. The conditions that mean stop now.

What is actually happening

The inducer starts first in every heating sequence. Before the control will go any further, it has to see the pressure switch close — a diaphragm switch connected by a small hose to the inducer housing, which closes when the inducer generates enough suction. That switch is what proves the flue is clear and the inducer is actually moving air. Until it closes, the control will not energise the igniter, and it will certainly not open the gas valve.

What causes it

In cold weather the most common cause is a blocked intake or exhaust termination outside — snow, ice, a bird's nest, or a plastic cap left on. Then: water in the pressure switch hose or in the condensate trap, a cracked, kinked or disconnected hose, a blocked condensate drain backing water into the collector box, a failing inducer that spins but does not develop enough suction, or a failed switch. An inducer that hums, spins slowly, or has a bearing noise will look alive and still not close the switch.

The codes that report this

22 codes across 10 control families. Each links to what that manufacturer says about it.

Brand	Code	What it reports
Armstrong	9 flashes	Pressure switch failed to close, or opened during a heat demand
Armstrong	10 flashes	Watchguard — pressure switch opened five times during one heat demand
Carrier	Status code 31	Pressure switch did not close, or reopened
Goodman	3 flashes	Pressure switch will not close
Goodman	9 flashes	High stage pressure switch stuck open
Goodman	E2	Low stage pressure switch stuck open
Goodman	E9	High stage pressure switch stuck open
Goodman	3 red flashes	First stage pressure switch stuck open, or an inducer error
Goodman	3 double red flashes	Second stage pressure switch stuck open, or an inducer error
Heil	3 flashes	Low pressure switch still open 30 seconds after the inducer started
Heil	9 flashes	High pressure switch open when it should be closed
Lennox	Alert code 223	Low pressure switch open
Lennox	Alert code 225	High pressure switch will not close
Lennox	Alert code 227	Low pressure switch open in run mode
Lennox	Alert code 271	Low pressure switch open — Watchguard
Lennox	Alert code 272	Low pressure switch open in run mode — Watchguard
Lennox	E227	Pressure switch opened during ignition or run
Lennox	E271	Soft lockout — retries exceeded, pressure switch opened
Lennox	E272	Soft lockout — recycles exceeded, pressure switch opened
Rheem	2 blinks	Pressure switch did not close within 10 seconds
York	3 red flashes	Pressure switch open, or first stage pressure switch open
York	3 double red flashes	Second stage pressure switch stuck open

Worth knowing

This is the furnace correctly refusing to burn gas because it cannot prove the flue is clear. Jumpering the pressure switch to force it to run defeats the interlock that stops combustion products entering the house.

Other symptoms

This site is a reference, not a substitute for a licensed HVAC technician. Gas appliances can leak carbon monoxide and cause fire. Anything involving gas lines, the heat exchanger, or the flame sensing circuit should be handled by a licensed professional. Pages are written with AI assistance from the sources listed on each page and checked against them before publishing.

Error codes behind this symptom

If your furnace is flashing a code while doing this, these code families are the usual suspects: inducer motor codes, pressure switch codes, igniter fault codes. Look your exact code up from the brand index, and see the furnace repair cost guide for what the fix typically runs.