Gas Furnace Won T Light

If your furnace does not have a pilot light move on to the next step.

Gas furnace won t light. Remove the front panel and look for the ignitor sensor. It is usually located near where the flames shoot out of the burners. To fix the furnace that won t start turn off the power to the furnace and turn off the gas. The orifice on the gas valve could be dirty or clogged as well.

If there is a leak if there isn t any gas in the reservoir or the valve from the reservoir is turned off. The codes are listed in a chart in the owner s manual and usually on a door or access panel on the furnace. Control boards are usually located inside the blower compartment of the furnace. If a failure occurs led lights on the control board light up in a blinking pattern to indicate a specific failure code.

Normally if you smell gas at the exhaust when the furnace kicks on it is a sign the gas valve is fine. This is why your furnace won t turn on. However even many modern furnaces still run pilot lights. Your furnace requires fuel to keep the pilot light engaged and the burners functioning.

Another possibility is a bad gas controller bad thermostat either furnace thermostat or household or a problem in the electrical controller like a stuck relay or a backup hydrostat safety thermostat clamped onto the outgoing hot water pipe if huydronic system that is telling the furnace it is too hot whether or not that is true.