Atwood Furnace: “2 flashes”
danger RV furnace fault codes
What it means
Two LED flashes followed by a 3-second pause, repeating. Indicates a flame sense fault: the board is not getting a valid flame-sense signal (for example it lit but could not confirm/hold the flame). This is a hard lockout for safety, so the furnace stops and must be manually reset.
Most likely causes
- Dirty, corroded, or sooted flame-sense electrode tip preventing a good flame signal most likely
- Poor ground at the burner/electrode (the flame-sense circuit needs a good ground path) common
- Electrode positioned wrong, cracked ceramic, or damaged sense wire common
- Weak flame from low gas pressure or partially clogged burner orifice, so the board loses the flame signal less common
Safe checks you can do yourself
- With power off, inspect the flame-sense/igniter electrode at the burner: clean a lightly oxidized tip with fine abrasive (e.g. fine sandpaper or a clean abrasive pad) and remove soot.
- Check that the electrode and its wire are intact, the ceramic is not cracked, and the ground connections at the burner are clean and tight.
- Confirm the propane tank is not empty and the gas valve is open, since starvation can show up as lost flame.
- After cleaning, reset and watch one cycle to see whether the flame is established and held.
How to reset / clear 2 flashes
- Turn the wall thermostat off and the setpoint all the way down; wait for the blower to stop.
- Remove 12V power from the furnace for about 30 seconds (a hard lockout requires a thermostat or power-switch reset).
- Restore power, turn the thermostat back on, and call for heat.
When to call a technician
Call a technician if the 2-flash code returns after cleaning/checking the electrode and ground, or if you suspect low gas pressure, a faulty gas valve, or a wiring fault. Repeated flame loss should be diagnosed professionally before continued use.
Applies to
AFMD16 · AFMD20 · AFMD25 · AFMD30 · AFMD35 · Atwood Hydroflame AFM/AFMD series furnaces with the standard 3-tries-for-ignition diagnostic control board
FAQ
What does Atwood Furnace code "2 flashes" mean?
Two LED flashes followed by a 3-second pause, repeating. Indicates a flame sense fault: the board is not getting a valid flame-sense signal (for example it lit but could not confirm/hold the flame). This is a hard lockout for safety, so the furnace stops and must be manually reset.
How do I reset Atwood Furnace 2 flashes?
Turn the wall thermostat off and the setpoint all the way down; wait for the blower to stop. Remove 12V power from the furnace for about 30 seconds (a hard lockout requires a thermostat or power-switch reset). Restore power, turn the thermostat back on, and call for heat.
What is the most common cause of 2 flashes on a Atwood Furnace?
The most likely cause is dirty, corroded, or sooted flame-sense electrode tip preventing a good flame signal.
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Sources
- Dometic (Atwood) Furnace Model AFM, AFMD Series Operating Instructions — Ignition Control Diagnostic Codes chart: 'Flame Sense Fault - 2-Flashes With 3-Second Pause - Hard' (Forest River, Inc. (OEM-hosted manufacturer document))
- Atwood Furnace AFM Operating/Service Manual — Diagnostic chart: Flame Sense Fault = 2 flashes with 3-second pause, Hard lockout (Atwood Mobile Products (Heartland Owners manuals library))
Note: Distinguish from the 3-flash 'ignition lockout' code: 2 flashes is specifically a flame-sense (hard) fault, whereas 3 flashes is a failure to ignite across the retry sequence. Some third-party summaries blur the two; the manufacturer chart keeps them separate.
● Last verified 2026-06-29 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual.