Error codes › Furnace (Forced-Air LP)

Furnace (Forced-Air LP) error codes

22 codes from 6 manufacturers, each with its meaning and the document it comes from. Open a code for the details, or search every system.

Atwood AFM (LED-blink) (4)

STEADY ONSteady-on LED with no flashing pattern indicates an internal failure on the ignition control module. HARD…
1 FLASHLimit switch is open or airflow is insufficient. SOFT lockout — auto-retries.
2 FLASHBurner lit but flame sense circuit failed to detect flame. HARD lockout — requires manual reset.
3 FLASHBurner did not light after 3 ignition attempts. SOFT lockout with 1-hour retry.

Steady on, no flashingInternal circuit board failure (HARD lockout) - the ignition control board has failed. A hard lockout…
1 flash with 3 s pauseLimit switch or airflow problems (SOFT lockout) - the high-temp limit opened or airflow is restricted. A soft…
2 flashes with 3 s pauseFlame sense fault (HARD lockout) - the board is not sensing a stable flame. Requires a manual reset…
3 flashes with 3 s pauseIgnition lockout fault (SOFT lockout, ~1 hour retry) - the control tried ignition three times and failed; it…
4 flashes with 3 s pauseHigh voltage (SOFT lockout) - supply voltage is high, 16 V to 17 V. The furnace soft-locks until voltage…
5 flashes with 3 s pauseLow voltage (SOFT lockout) - supply voltage is low, 8 V to 9 V. The furnace soft-locks until voltage recovers.

LOCKOUTFailure to ignite (general LOCKOUT - no numbered F-code on this platform; reported by Diagnose PCB LED…

30-sec sail lockoutBlower is running but the sail switch didn't close within 30 seconds of the blower starting — module board…
3-trial ignition lockoutThree failed Trial-For-Ignition attempts — module board has de-energized the gas valve and gone to lockout.…
Flame sense <7 µAUnits with a separate flame-sensor probe only (remote sense): the burner lights but the flame-sensor current…

W 25 HOver-voltage at the heater: battery > 16.4 VDC. Heater self-recovers when voltage drops.
W 26 HUnder-voltage: battery voltage < 10 V. Heater shuts down to protect itself.
W 29 HImminent under-voltage: battery < 10.4 V (early warning before W 26 H lockout).
W 255 HNo 12 VDC at heater OR no TIN-bus comms between heater and CP Plus control panel.
E 2 HFlame not recognised: the ignition trial completed but the control did not detect a flame. (The cited…
W 27 HWarm-air outlets blocked or circulated-air intake blocked.
W 28 HWindow above the exhaust cowl is open (window switch): the CP Plus inhibits the heater while a window near…