FurnaceTroubleshooting2026-01-25
Furnace Pilot Light or Ignition Keeps Going Out
A pilot or ignition that won't stay lit usually points to the thermocouple, flame sensor or gas supply.
Older furnaces use a standing pilot; newer ones use electronic ignition. Both can fail to stay lit for similar reasons.
Standing pilot furnaces
If the pilot won't stay lit, the thermocouple is the usual culprit — it senses the flame and shuts the gas off when it fails. Drafts and a dirty pilot orifice also cause outages.
Electronic ignition furnaces
On modern units, a dirty flame sensor, failing igniter, or gas supply issue causes ignition lockouts. These need a technician rather than a relight.
Key takeaways
- Don't keep relighting a furnace that won't stay lit
- A failing thermocouple is a common, inexpensive fix
- Have the flame sensor cleaned during service
- Rule out low gas pressure
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