Atwood AFMD series fault codes
The 4 fault codes below are the ones that apply to this Atwood furnace family. The other 2 Atwood furnace codes in our database belong to different model families — they are listed further down so you do not troubleshoot against the wrong table.
Covered model numbers
AFMD16AFMD20AFMD25AFMD30AFMD35
Not on the list? Check the rating label before you troubleshoot — the code table below will not apply. Where to find it →
Fault codes on the Atwood AFMD series
One LED flash followed by a 3-second pause, repeating. Indicates a limit switch / airflow … 2 flashes danger
Two LED flashes followed by a 3-second pause, repeating. Indicates a flame sense fault: th… 3 flashes warning
Three LED flashes followed by a 3-second pause, repeating. Indicates an ignition lockout f… Steady on (no flash) danger
The diagnostic LED on the ignition control board is on continuously with no flashing, indi…
Codes that do not apply to this model
These 2 codes exist on other Atwood furnaces. If your unit is showing one of them, it is not from this family — re-check the model number on the label before acting on any of these.
On a 2-stage Excalibur furnace control board, four flashes of the diagnostic LED report a … 5 flashes
On a 2-stage Excalibur furnace control board, five flashes indicate a module (control boar…
Where the model number is
On the furnace casing itself, reachable through the return-air grille or the exterior access door, not on the thermostat.
Sources
- Dometic (Atwood) Furnace Model AFM, AFMD Series Operating Instructions — Forest River, Inc. (OEM-hosted manufacturer document) (Ignition Control Diagnostic Codes chart (Standard 3 Tries for Ignition Controls): 'Internal Circuit Board Failure - Steady On, No Flashing - Hard' lockout)
- Atwood Furnace AFM Operating/Service Manual — Atwood Mobile Products (Heartland Owners manuals library) (Diagnostic chart: Flame Sense Fault = 2 flashes with 3-second pause, Hard lockout)
- Atwood Shop/Service Manual - HydroFlame (2-stage furnace diagnostics section) — Atwood Mobile Products (service manual hosted by My RV Works) (Sequence of operation/limit-switch section: control will 'lock out (three try for ignition, one hour lockout and then three retry)'; diagnostic chart defines LED flash codes)
- Atwood Furnace AFM Operating/Service Manual — Atwood Mobile Products (manual hosted at Heartland Owners manuals library) (Ignition Control Diagnostic Codes: Internal Circuit Board Failure = Steady On, No Flashing, Hard lockout; covers models AFMD16/20/25/30/35)
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