York/Coleman/Luxaire furnace flash codes, decoded
Applies to: York, Coleman, and Luxaire gas furnaces (shared platform)
What this error means
The shared-platform LED language: slow GREEN flash = normal standby, slow AMBER flash = normal heating call. Red fault flashes: 1 = flame detected with gas off (SAFETY), 2 = pressure switch stuck closed, 3 = stuck open (venting/inducer/condensate), 4 = limit open (airflow/filter), 5 = rollout open (SAFETY), 6 = lockout from repeated pressure-switch events, 7 = ignition lockout after retries (auto-resets after ~60 minutes; flame sensor territory), 8 = flame lost repeatedly, 9 = grounding/polarity fault, 10 = gas valve wiring fault (SAFETY), 11 = extended limit (blower suspect), 12 = igniter failure. Steady-ON LED = board fault. Bonus: on many boards, holding the LAST ERROR button 5+ seconds replays/clears the stored code.
Symptoms
- Counted red flashes on the board LED
- Green/amber flashing (that's normal — check the pattern before worrying)
Try this first (safe DIY steps)
- Identify color first: slow green/amber = normal operation
- Count red flashes and record
- 4 or 11: filter and registers
- 3 or 6: exterior vent terminations and condensate
- 7: flame sensor cleaning; one power cycle or wait out the 60-minute auto-reset
- 1, 5, or 10: shut the furnace off and call — gas/flame safety events
Safety: power off before any physical intervention. Never bypass covers or interlocks — fuser areas run hot enough to burn.
When to call a technician
Codes 1, 5, 10 = professional only. Steady-on LED = control board replacement ($400–700 installed).