Lennox · Furnace / HVAC
5 blinks Flame rollout switch open
What this code means
A safety switch tripped because flame escaped the burner area instead of staying contained in the combustion chamber — a serious safety-critical fault.
Most likely causes
- Blocked flue or exhaust venting
- Cracked heat exchanger
- Dirty or damaged burners
What to try first
Turn the system off and don't reset repeatedly — this specific fault should always be inspected by a professional before running the furnace again.
Safety first: stop using the appliance and shut off its gas or power until it has been inspected — this fault category is associated with fire or gas risk.
FAQ
What does Lennox error code 5 blinks mean?
Flame rollout switch open. A safety switch tripped because flame escaped the burner area instead of staying contained in the combustion chamber — a serious safety-critical fault.
Can I fix Lennox code 5 blinks myself?
No — stop using the appliance and shut off its gas or power until it has been inspected. This fault category is associated with fire or gas risk.
What causes Lennox code 5 blinks?
The most common causes are: blocked flue or exhaust venting; cracked heat exchanger; dirty or damaged burners.
Other Lennox furnace codes
All Lennox furnace error codes →
Other furnace brands: Trane · Carrier · Goodman · Amana · American Standard · Rheem · Bryant · Generic · Nest
This information may contain errors or not apply to your exact model — always double-check it against your appliance's own manual before acting. If there's any chance of a gas, fire, electrical, carbon monoxide, or other safety hazard, stop and call a licensed professional or the appropriate agency (e.g. your gas utility) instead of relying on this page alone.