Uploaded February 2021 | Updated September 2026, 2 weeks ago

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If your furnace lights and then shuts down about 4 seconds later following a noticeable pattern, your flame sensor is probably the culprit. You can clean it and it might solve your problem for free. Always check for proper ventilation, a clean filter, and a clear gas flow. Shut off the power before you go inside. I am just a history teacher with a bit too much confidence for my own good so consult a professional if you are unsure.