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Furnace Blinking 6 Times: What It Means and How to Fix It

Furnace guide · Decoded from manufacturer documentation · Safe homeowner checks only, gas and wiring work is professional only

Why this happens

A furnace control board watches a chain of safety devices before and during every heat cycle, and it reports a break in that chain as a blink count. The trouble with six blinks is that different manufacturers assign the same count to different links in the chain, because there is no universal blink standard across brands. On Goodman models the board lists six flashes as an open rollout switch, a small heat sensitive safety device above the burners that opens when flames or excess heat escape the burner box, caused by blocked venting, a weak inducer, a blocked or cracked heat exchanger, or a switch weakened with age. On York models six red blinks point instead at the modulating gas valve, the part that meters gas to the burners, and a valve that cannot modulate or seal correctly will lock the furnace out rather than risk an uncontrolled flame. On American Standard models six blinks point at reversed polarity, meaning the line and neutral conductors of the furnace supply are swapped, which some control boards detect and refuse to run on. Rheem reports vary further, with some six blink cases tracing to an inducer that never starts, a board or wiring fault rather than a burner fault. Two neighbours with the same blink count can therefore have entirely different faults, which is why the door chart, not a general table, decides the diagnosis.

Finding the cause

The door chart decides what 6 blinks means on your furnace

This is the first check and the one that makes the rest of the guide usable. Count the flashes carefully, note the pause between groups, and read the chart printed inside the blower door or on the back of the top door. Goodman charts list six flashes as an open rollout switch. York charts and York guidance describe six red blinks as a modulating gas valve failure. American Standard guidance describes six blinks as a polarity fault. If your chart says something else, your chart wins, and the checks below still apply in the same order, because filter, vent, inducer sound, and one reset are relevant to every version of the fault. If the chart is missing, faded, or unreadable, treat the meaning as unknown and call a professional rather than guessing from a brand table, since a rollout fault and a polarity fault are repaired by different trades and neither is a homeowner job. Write down the exact wording from your chart before calling anyone, because a technician who hears the brand meaning on the first call arrives with the right parts and the right tests.

A blocked vent termination or a dirty filter is pushing the furnace toward a rollout trip

On the Goodman rollout version of six blinks, the exhaust path is the first physical check, because a restriction there produces exactly the pressure that makes flames roll out of the burner box. Go outside and find where your furnace vents: a plastic pipe termination on a side wall on a high efficiency furnace, or a metal flue into a chimney on an older one. Look for snow piled against the pipes, ice at the openings, leaves, a nest, or a screen clogged with debris, and check the intake pipe too if your furnace has one, because a starved intake disturbs the burn just as a blocked exhaust does. Clear anything you can reach safely from the ground, and check the filter as well, holding it up to a light and replacing it if light barely passes, because a starved furnace runs hot at the burners. This check matters because it is one of the few rollout causes a homeowner can genuinely fix: if the code clears after the termination is cleared and stays clear through a full heat cycle, the blockage was the story. If the termination was already clear, or the code returns, the restriction is inside the furnace or the flue run, and that is professional territory. Do not put anything into the flue, and never run the furnace with the vent knowingly blocked to keep the house warm.

Scorch signs near the burners confirm a real rollout on the Goodman version

A rollout event often leaves evidence, and reading that evidence from outside the furnace tells you how urgent the Goodman version of this code is. With the furnace off, look at the burner area through the sight glass if your model has one, and look at the outside of the cabinet around the burner access panel. Warning signs are blackened or blistered paint above the burner openings, soot streaks climbing the front of the heat exchanger area, wire insulation near the burners that looks melted, softened, or discolored, and a sharp burnt smell around the furnace. Any one of these means flame genuinely escaped the burner box, and the furnace should stay off until a technician finds out why, because one possible cause is a cracked heat exchanger, which is a carbon monoxide risk. Do not open the burner compartment to look closer: the observation is for triage, not diagnosis, and opening that compartment is professional work. Write down exactly what you saw and where, because scorch location helps a technician judge whether the cause is venting, the inducer, or the heat exchanger. If you find no scorch signs at all and the vent termination was blocked, a nuisance trip from the blockage alone is plausible, which the reset test below will help settle.

The inducer never starting separates a power or board fault from a burner fault

The inducer fan starts before ignition on every heat cycle, and its behaviour during a call for heat is the most useful sound check in this guide. Stand near the furnace during a call for heat, with all access panels closed, and listen to the sequence. You should hear the inducer start first and run steadily, then ignition, then the main blower. An inducer that never starts at all, while the thermostat is calling for heat and the furnace power switch is on, points away from the burners and toward power, wiring, or the control board, which matches the Rheem pattern where six blinks arrive with an inducer that never receives power. An inducer that starts and runs steadily but is followed by a lockout points back toward the rollout, gas valve, or polarity versions of the fault, depending on your door chart. This check is listen only, from outside the furnace. Do not open the compartment, touch the inducer, or test its wiring: it sits among hot surfaces, gas parts, and live electrical components. Note what you heard and at what point in the sequence the furnace locked out, because that timing separates an inducer power problem from a burner problem.

Recent electrical work points toward the polarity version on American Standard models

Reversed polarity does not develop on its own in a furnace that has run correctly for years, so its history check is different from the others. Ask whether any electrical work has happened recently: a new furnace installation, a replaced control board, a moved outlet or disconnect, rewiring after a renovation, or work on the panel that feeds the furnace. A polarity fault that appears right after such work is strong circumstantial evidence for the American Standard meaning, and it also tells you which trade to call, an electrician or the installing HVAC company, rather than a burner technician. There is no homeowner test for polarity on a hardwired furnace: confirming it means testing mains conductors inside the furnace wiring compartment, which is professional work with live voltage. Do not swap wires, do not open the junction box, and do not assume the fault is polarity just because it is on the list. If no electrical work has happened and your door chart still says polarity, the fault may be a failing board misreading its supply, which is again a professional diagnosis. Report the work history exactly as it happened, including dates, because it saves a technician a return visit.

A gas valve fault on the York version shows as ignition that never settles

On the York gas valve version, the pattern to listen for is a furnace that tries to light and never settles into a steady flame. You may hear the inducer start normally, then ignition attempts that fail, or a flame that lights for a few seconds and drops out, followed by lockout and six blinks. That pattern is consistent with a modulating gas valve that cannot meter gas correctly, but it is not proof of it, because a contaminated flame sensor, a weak igniter, or a control board fault can produce a similar failed ignition sequence. The distinction matters only to the technician, who will test the valve, the sensor, and the board in turn, and it is exactly why this guide stops at observation. Do not touch the gas valve, do not adjust any gas pressure screw, and do not repeatedly cycle the furnace to see if it eventually catches, because repeated failed ignition attempts with a faulty valve are not a safe experiment. One reset test after the external checks is the homeowner limit. If the York pattern repeats after that single reset, the furnace stays off and the call goes to a professional, with the ignition pattern described exactly as you heard it.

Fixing it

1. Record the pattern and read your door chart, about 5 minutes. Count the flashes and the pause, note whether the pattern repeats steadily, and copy the exact wording from the chart inside the blower door. If the chart is missing or unreadable, stop here and call a professional.
2. Check thermostat, switch, breaker, and filter, about 10 minutes. Confirm the thermostat is set to Heat and above room temperature, the furnace power switch is on, the breaker is on, and the filter passes light when held up to it. Replace a clogged filter with the correct size.
3. Clear the outside vent or flue termination, about 15 minutes. Remove snow, ice, leaves, nests, or debris from the exhaust and intake terminations, working only from the ground and only from outside. Do not insert anything into the flue.
4. Look for scorch signs, about 5 minutes. Check the sight glass and the cabinet around the burner panel for blackened paint, soot streaks, or melted looking wire insulation. If you find any, skip the reset test entirely and call a professional with the furnace left off.
5. Listen to one heat call, about 5 minutes. With all panels closed, listen for the inducer first, then ignition, then the blower. Note whether the inducer never starts, or starts and the furnace locks out after ignition attempts, because that timing tells the technician which fault family to test first.
6. Reset once and observe one full cycle, about 15 minutes. With no scorch signs found, switch the furnace power off, wait at least 30 seconds, switch it back on, and watch one complete heat cycle from outside the furnace. If 6 blinks return at any point, switch the furnace off and call a professional. Do not reset a second time, never bypass a rollout switch, and never adjust a gas valve or swap wiring to keep the heat on.

What it costs

Vent and filter first; switch, valve, board, or wiring last. The free external checks are the cheap outcomes. Every internal version of this code is a professional repair, and the price spread below reflects how different the Goodman, York, and American Standard faults really are.

All prices on this page are estimates based on typical US parts and service pricing. Your model, region and the actual failed part will move the real figure.

Repair or replace note: a rollout switch, a polarity correction, or a gas valve repair is almost always worth doing, since each fitted cost is a small fraction of a replacement furnace. A control board repair on a furnace over 15 years old needs the heat exchanger checked first, because there is no sense fitting a new board to a furnace whose exchanger then fails inspection. A condemned heat exchanger almost always means a new furnace, typically $3,500 to $7,500 installed (estimate). The full pattern list is on the furnace blink codes hub, and the companion patterns are the furnace blinking 5 times guide and the furnace blinking 4 times guide.

Mistakes that make it worse

• Assuming 6 blinks means one thing on every brand. Rollout, gas valve, and polarity are different faults repaired by different tests. Check your door chart first, every time.
• Bypassing or jumping the rollout switch on the Goodman version. This defeats the device that detects flames escaping the burner box. It can allow a fire at the front of the furnace and removes the warning that a heat exchanger may be cracked. Never do it, even temporarily.
• Repeatedly resetting to keep the heat on. Each reset after a genuine fault lets the failure repeat, damages wiring and controls near the burners, and hides the trip pattern a technician needs to see.
• Running the furnace with a blocked vent to get through the night. A blocked exhaust is a leading rollout cause and a carbon monoxide risk. Clear the termination or leave the furnace off.
• Opening a wiring compartment to check polarity yourself. Polarity testing means working with live mains conductors inside the furnace. That is electrician work, not a homeowner check, however simple it sounds.
• Adjusting a gas valve or its pressure screws. Gas valve adjustment changes the fuel supply to the burners and can create an unsafe flame or a gas leak. No homeowner adjustment is ever part of this code.
• Ignoring scorch marks or a burnt smell. Those are the physical evidence that rollout really happened. A furnace showing them stays off until it is inspected.

Frequently Asked Questions

Related Guides

• Furnace Blinking 5 Times: What It Means and How to Fix It
• Furnace Blinking 4 Times: What It Means and How to Fix It
• Furnace Blinking 3 Times: What It Means and How to Fix It

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