Napoleon gas furnaces are built by Wolf Steel in Barrie, Ontario — the W at the front of the model number stands for Wolf Steel, and the letter after it tells you the tier: S for the Essential line, P for Premium, U for Ultimate. That matters when you are looking up a code, because the diagnostic table has stayed remarkably consistent across the 9200, 9500, 9600 and 9700 series for well over a decade. A flash count you look up for a 9600 will almost always be right on a current 9700.
There are two lights on the board, and people mix them up constantly. The red status LED is the one that reports faults. The second LED beside it only reports the high-heat stage: off means no demand for second stage, steady on means second stage is running normally, and flashing means the furnace wants high heat but the high pressure switch has not closed. On the 9600 and 9700 that second light is yellow; on the current Ultimate series board it is green. A flashing second light is not an error code, and counting its blinks will send you looking up the wrong fault.
The board also keeps a history. Press the push-button switch on the control and release it, and the furnace flashes the last five stored fault codes in order, most recent first — genuinely useful when a furnace misbehaves overnight and is running fine by the time anyone looks at it. Holding that button for more than five seconds clears the history. As always, codes vary by model and the diagnostic label inside the furnace panel is the authority: where this page and that label disagree, believe the label. If you would rather have someone else read it, our Napoleon furnace repair page explains what we check first, or just get in touch.
Napoleon furnace codes, decoded
| Code | What it means | Safe? | Try first | When to call |
|---|---|---|---|---|
LED off | No power reaching the control, or the board has detected a hardware fault in itself. | turn it off | Check the service switch, the furnace door switch and the breaker. | If power is confirmed and the light stays dark. |
LED steady on | Normal operation. No stored fault is being reported. | keep running | Nothing. This is the light you want to see. | Not needed for this state. |
1 flash | High limit switch open — the furnace is running hotter than the limit allows. | turn it off | Change the filter and open every supply register in the house. | If it comes back with a clean filter and open vents. |
2 flashes | Pressure switch open while the exhauster is running. If the switch does not close within 60 seconds the board shuts the exhauster down for an hour. | turn it off | Check the outside intake and exhaust terminations for snow or ice. | If the terminations are clear, or if the trap holds water. |
3 flashes | Pressure switch closed while the exhauster is off — the switch is stuck closed. | turn it off | Nothing at home. A stuck switch defeats a venting safety. | Right away. Do not run the furnace on this one. |
4 flashes | Lockout after too many failed ignition attempts. The furnace resets itself after one hour. | turn it off | Confirm the gas is on and the shutoff at the furnace is open. | Same day if the house is cold. This is the common no-heat code. |
5 flashes | Line and neutral polarity problem — the incoming 120-volt supply is reversed. | turn it off | Nothing at home. This is electrical work. | Yes. Common right after an install or panel work. |
6 flashes | Too many limit trips within a single call for heat. | turn it off | New filter, check for closed dampers and a blocked return grille. | If airflow looks clear. Repeated overheating needs eyes on it. |
7 flashes | Pressure switch cycle lockout — the switch has opened and closed too many times. | turn it off | Look for a blocked condensate trap or a vent pipe holding water. | Yes. Usually venting or condensate rather than the switch itself. |
8 flashes | Lockout after too many flame dropouts. The board allows up to five flame losses in one heat call, then locks out for an hour. | turn it off | Change a dirty filter, then leave it alone through the lockout. | Soon. Flame that lights and dies points at the sensor or the gas supply. |
10 flashes | Flame present with the gas valve off — the furnace can see fire when there should be none. | call now | Turn the furnace off at the service switch and keep it off. | Immediately. A valve passing gas is a real safety fault. |
High-heat LED off | No demand for second-stage heat. Normal on a mild day. | keep running | Nothing. This is not a fault indicator. | Not needed for this state. |
High-heat LED on | Second-stage heat is being called for and is operating normally. | keep running | Nothing. | Not needed for this state. |
High-heat LED flashing | The furnace wants high heat but the high pressure switch has not closed, so it stays on first stage. | turn it off | Check the vent terminations outside, then watch whether the house keeps up. | If the furnace cannot hold temperature on the coldest nights. |
The codes that usually mean a real repair
Four flashes — the ignition sequence never proved flame
This is the code that brings us out most often on a Napoleon. The board tried to light the burners, failed the allowed number of times, and shut itself down for an hour. The usual causes are a hot surface igniter at the end of its life, a flame sensor coated in oxide, or gas supply that is not reaching the valve properly. A flame sensor cleaning or replacement runs $150–$300 and a hot surface igniter is $200–$450, both single-visit repairs. The tell is whether you hear the igniter glow and the burners try: no attempt at all points at the igniter or the board, an attempt that lights and dies points at the sensor.
Two or seven flashes — venting, condensate and the pressure switch
Pressure switch codes on a Napoleon 9600 or 9700 are more often a blocked path than a bad switch. These are condensing furnaces, so they drain, and the trap under the cabinet silts up over a few seasons. Side-wall vent terminations also ice over during the freeze-thaw swings we get off Lake Ontario, and a plugged termination reads at the board exactly like a failed switch. Clearing or replacing a blocked trap runs $150–$350; a pressure switch itself sits in the $250–$500 band. Diagnose before replacing, or the new switch fails the same way within the week.
One or six flashes — the furnace is overheating
Limit codes mean heat is building up faster than the blower can move it away, and the fix is almost always airflow rather than the limit switch. Start with the filter, then closed registers, then a return grille blocked by furniture or a finished-basement renovation that never got a proper return. If those are clear, the blower itself is the suspect: a motor running slow or a wheel packed with dust. Replacing a blower motor lands between $500–$1,500, with variable-speed ECM motors sitting at the top of that band. Repeated overheating is hard on a heat exchanger, so it is worth sorting out rather than resetting — our guide to furnace short-cycling covers what the pattern usually means.
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Common questions
Where is the status light on a Napoleon furnace?
On the integrated control board behind the lower front door. Most Napoleon furnaces have a small sight glass or window in that door so you can watch the light without opening anything, which matters because pulling the door usually cuts power through the door switch and wipes what you were trying to read. Watch through the window, count the flashes from the first blink after the long pause, and watch at least three full cycles before deciding on a number.
Can I see what went wrong last night if the furnace is running now?
Yes, and this is one of the more useful things about these boards. Napoleon controls store the last five fault codes. Press and release the push-button switch on the control and the board flashes them back in order, most recent first, oldest last. That turns an intermittent overnight fault into something a technician can actually chase. Holding the same button for more than five seconds clears the stored history, so avoid leaning on it before your service visit.
What does five flashes mean on a Napoleon furnace?
Reversed line and neutral polarity on the 120-volt supply feeding the furnace. The control needs a correct hot and neutral to sense flame properly, so it refuses to run rather than operating blind. We see this after a furnace has been moved, after a panel or receptacle change, and occasionally on an older Burlington or Hamilton house where an outlet was rewired at some point by someone working quickly. It is not something to solve at home — it is electrical work, and the furnace will keep flashing five until the supply is corrected.
Are Napoleon furnaces still made, and does that affect parts?
Yes. Napoleon still builds residential gas furnaces at Wolf Steel in Barrie, Ontario, and the current line runs from the Essential series through the Premium 9600 to the Ultimate 9700. The 9200 series has been superseded, so if that is what you have, expect an older parts picture than a 9600 or 9700 owner. Napoleon is better known publicly for grills and fireplaces than for furnaces, which is why homeowners are sometimes told the brand no longer exists in HVAC. It does.
The furnace locked out but started again an hour later. Is it fixed?
No — it timed out, which is not the same thing. Both the ignition lockout and the flame-dropout lockout on a Napoleon board are one-hour timeouts, so the furnace retries on its own whether or not anything was corrected. A furnace that limps through a cold week on hourly retries is one that will quit properly on the coldest night of the year. If yours is cycling like that, book a look at it before it becomes an emergency call, or read what to do when the heat stops at night.