Why Won't My Gas Furnace Stay Lit?

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Why Won't My Gas Furnace Stay Lit?

Have you ever become frustrated on a cold winter day as your furnace keeps shutting off? It even becomes worse if it lights up for a couple of minutes then instantly loses its flame on its own. There are several reasons why this happens. While you can simply call an HVAC professional to sort it out, it’s actually best to figure what causes this issue. Here are several reasons why your gas furnace won’t stay lit.

How Your Furnace Ignites

For starters, you might wonder how your furnace works and provides warmth to your home. There are actually two types of furnaces that households have.

A direct ignition furnace works by relying on a thermostat when to heat up, the fan turns on, and the gas valve proceeds to turn on the burner by blowing gas.

A furnace with a pilot light also works similarly, except that you have to turn the pilot light on your own first. This an old type of furnace, so turning it on works manually.

Situation 1: The Pilot Light Ignites, But Doesn’t Stay Lit Before Lighting Burner

Malfunctioning Flame Sensor

The flame sensor gives a signal to the furnace that the gas is already lit. This comes in handy since it prevents the furnace from continuously allowing gas to flow into your room. Once it malfunctions, it will indicate your furnace to do the opposite, even when the pilot light is out. If this is the main culprit, your flame sensor needs to be replaced immediately.

Wrong Flame Sensor Positioning

The flame sensor might work, but it’s positioned poorly on your furnace. This might not detect the pilot’s flame accordingly.

Bad Ignition Board

The ignition board is responsible for controlling the gas flow. Once it malfunctions, the ignition sequence is affected, and your gas furnace won’t stay lit.

Limited Gas Pressure

If the amount of gas pressure is not enough, it will affect the thermocouple. You can only sort out this problem by adjusting or replacing the gas valve.

Gas Furnace Repair

Situation 2: Burner Lights Up Before Heating Your Home


Once the heat exchanger gets hotter, your gas furnace will also overheat. This is typically caused by closed vents and dirty filters. Remember that you have to open your air vents, even inside unused rooms, and change your filters regularly.

Malfunctioning Limit Switch

The furnace’s limit switch is no longer working properly. If this is the case, it needs to be replaced.

Inaccurate Temperature Reading

Your thermostat might be the main culprit by indicating that your house is warm enough. This shuts down the burners immediately.

Poor Flame Sensor

If you have a direct ignition furnace, a poor flame sensor won’t detect a flame, causing the burner to shut off on its own.

Key Takeaway: What to Do?

A lot of households rely on gas furnaces as their main heating source. The tips mentioned above can be a great help to diagnose the main problem. And once you’ve figured out where the issue comes from, it’s time to call your local heating professional.

A repair expert can provide the right advice and consider repair or replacement services. Once fixed, your gas furnace will stay lit, keeping you warm and cozy inside your home. Got questions and concerns? Our team is ready to help. Call us today!

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