Direct answer
Furnace flame sensor proves burner flame so gas can remain on. Related symptoms include burners light then stop, ignition lockout or flame-sense code. Those symptoms do not prove the component failed: record the sequence and exact code before assuming contamination.
What this covers
- gas furnaces
- The exact condition described in the title
- Customer-accessible checks before internal repair or reset
What it does not cover
- ×A different brand, model family or similar-looking code
- ×Internal live-electrical, gas, refrigerant or sealed-system testing
- ×A guarantee that a named component has failed without isolation
Capture the exact state
ReversibleRecord the model, exact code, operating stage and whether the product completes the action this component supports.
Separate the likely fault domains
Reversiblerecord the sequence and exact code before assuming contamination.
Correct only the proven, accessible condition
ReversibleCorrect the external prerequisite first. Replacement difficulty is professional unless the exact manual permits customer maintenance.
Verify once before going farther
ReversibleRepeat the same controlled stage and confirm the symptom and stored code stay gone.
Evidence ledger
Sources behind this answer
Visible sources support the visible claims. Home Product Support records the publisher, the fact used and the review date; community reports can suggest an issue but do not become a published fact on their own.
Exact questions
Common follow-ups
What should I record first for “Furnace flame sensor: function, symptoms, testing boundary and repair difficulty”?+
Record the model, exact code, operating stage and whether the product completes the action this component supports.
Does the symptom or code prove a part has failed?+
No. record the sequence and exact code before assuming contamination.
When should I stop troubleshooting?+
Stop for gas odor, soot, rollout, CO alarm or damaged venting.
Answer for the exact device and software version shown above.