Turn the furnace off and do not reset it. If you smell gas, leave the building without operating switches and contact the gas utility or emergency services from outside.
What does Lennox code 275 mean?
Lennox furnace code 275 means flame had been sensed out of sequence; the flame signal is now gone and the furnace is in soft lockout on the supported control family. Confirm the model number and diagnostic chart inside the furnace door before replacing parts.
What causes Lennox code 275?
- A gas valve leaking or stuck open
- A shorted flame-sensing circuit
- A failed integrated control board
Can I troubleshoot Lennox code 275?
Turn the furnace off and do not reset it. If you smell gas, leave the building without operating switches and contact the gas utility or emergency services from outside.
How much does Lennox code 275 cost to fix?
A gas valve replacement typically costs between $300 and $1,000 nationally.
When should I call a technician?
Turn the furnace off and call a licensed technician immediately to test the gas valve and flame-proving circuit.
Sources and model scope
Fault codes vary by model and control board. Confirm the diagnostic chart inside your furnace panel or the official manual before acting.
Scope used here: Lennox integrated controls covered by installation instructions 508001-02D.
- Lennox Industries: Installation Instructions — Integrated Control Diagnostic Codes
508001-02D · Lennox furnaces explicitly covered by installation instructions 508001-02D; not a universal Lennox code list.
Compiled by Warmlo Editorial · Reviewed August 2026
This is general information, not professional advice. Gas, electrical, and combustion repairs can be dangerous — when in doubt, call a licensed technician.