New Dometic (Atwood) Furnace not staying lit

[Slo_Rollin']

Just purchased a new 2020 Windsport 34J. Drove it from TX to CO. Furnace worked great in TX, had fits entering CO, around 4500'. Furnace troubleshooting checks out, good power, good gas in the tank, water heater works, stove works. Sail switch is opening, igniter is igniting, fuel is lighting. Fan comes on with thermostat, ignition occurs, but won't remain lit. Is it the regulator? Is it the elevation (approx. 6000')? is it TX gas mix? I've had 2 previous RVs at elevation with CO propane, without issues.

[OldWEB]

FAULT LED INDICATION LOCKOUT
Internal Circuit Board Failure Steady On, No Flashing
Limit Switch/Airflow Problems 1 Flash With 3-Second Pause
Flame Sense Fault 2 Flashes With 3-Second Pause
Ignition Lockout Fault 3 Flashes With 3-Second Pause (1 hour retry)


Instruction manual may help.
Also if one or more vents are blocked, inhibiting airflow, could cause a shutdown.

[Raeburn2000]

One thing that got us earlier this winter was rust plugging the holes in the burner assembly. Similar symptoms to what you are describing. Had someone take the burner apart and clean the holes out on the assembly.

Repair man said that if it lights, then all the permissive (sail switch, fuel pressure, flame sensor) must all be working. We never saw any error codes while troubleshooting. Repair man was on phone with Atwood for 45 minutes and they couldn’t explain the symptoms. Another repair man said that the burner assembly rusts on the inside due tot the high humidity. Took it apart and the assembly was approx 80% plugged.