Atwood Furnace: “5 flashes”
warning RV furnace fault codes
What it means
On a 2-stage Excalibur furnace control board, five flashes indicate a module (control board) fault. The board's internal self-check failed, so it shuts the furnace down. This is a HARD lockout and usually points to the control module itself rather than an external switch.
Most likely causes
- Internal microprocessor or control module failure most likely
- Power-supply problems or voltage spikes that corrupted the board's self-test common
- Loose or corroded main connector at the board less common
Safe checks you can do yourself
- Turn the furnace off at the thermostat and power switch before inspecting.
- Check the 12V battery voltage and that connections at the furnace are clean and tight (low/dirty power can trigger faults).
- Inspect the main wiring connector on the board for corrosion or partial seating.
- Try one full power-off/power-on reset to confirm the code is persistent and not a one-time glitch.
How to reset / clear 5 flashes
- Set thermostat to OFF.
- Turn the furnace power switch off for about 30 seconds.
- Restore power and call for heat; if 5 flashes return, the module fault is persistent.
When to call a technician
If a power reset does not clear the 5-flash code, have a certified RV technician confirm the diagnosis and replace the control module with the correct OEM board.
Applies to
Atwood/Dometic 2-stage Excalibur furnaces · Model 1522 · Model 2334 · Model 2540
FAQ
What does Atwood Furnace code "5 flashes" mean?
On a 2-stage Excalibur furnace control board, five flashes indicate a module (control board) fault. The board's internal self-check failed, so it shuts the furnace down. This is a HARD lockout and usually points to the control module itself rather than an external switch.
How do I reset Atwood Furnace 5 flashes?
Set thermostat to OFF. Turn the furnace power switch off for about 30 seconds. Restore power and call for heat; if 5 flashes return, the module fault is persistent.
What is the most common cause of 5 flashes on a Atwood Furnace?
The most likely cause is internal microprocessor or control module failure.
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Sources
- Atwood Shop Manual - HydroFlame Furnaces (2-Stage Furnace Diagnostics chart) — Diagnostic Chart - 2-Stage Furnace Diagnostics: 5 flashes = Module Fault (HARD) (Atwood Mobile Products / hosted by MyRVWorks)
Note: Specific to the 2-stage Excalibur board (models 1522, 2334, 2540). A genuine module fault is uncommon; rule out low battery voltage and connector issues first. Single-stage 85xx boards do not use this 5-flash code.
● Last verified 2026-06-29 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual.