Fault codes / RV furnace / 3 FLASHES (3 s pause)

RV furnace: 3 flashes (3 s pause)

What it means: Ignition lockout.

What to check

Gas supply/pressure, spark, valve. Reset by cycling the thermostat or power.

Learn the system

• Furnace sequence
• LP system basics

Practice it on a service call

• Furnace blows cold
• Furnace sparks but never lights
• Furnace keeps shutting off, fan keeps blowing

Guided diagnosis

• Furnace
• Thermostat

Other RV furnace codes

• RV furnace: 1 flash (3 s pause) Air flow / limit fault
• RV furnace: 2 flashes (3 s pause) Flame sense fault
• RV furnace: Steady on Internal control failure

Full field guide: Suburban and Atwood (Dometic) furnace board

Codes come from the maker manuals and public service sheets. Your model's own chart always wins, and LP and 120 volt work belongs to a qualified technician.