Igniter glows but burners never light

If the igniter glows and no flame appears, the problem is on the gas side (supply off, valve not opening, valve not receiving 24 V). You can confirm the gas shutoff is open and whether the board sends the valve signal; the valve and gas pressure are licensed-technician work.

Single source ~30 min advancedBrands: All

Before you start

If you smell gas: do not operate switches or the furnace, leave the building and call the gas utility from outside.
Make sure the home has a working carbon monoxide (CO) alarm; if it is sounding or anyone has headache/nausea, get everyone out and call 911 / the gas utility.
Turn off power at the furnace service switch or breaker before opening the burner or blower compartment; the door switch alone is not a lockout.
Gas-side diagnosis or repair (gas valve, gas pressure, burners, heat exchanger, venting) is for a licensed gas/HVAC technician only.
Never jumper or bypass a limit, rollout or pressure switch.

Diagnostic steps

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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

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