back to blog

6 Reasons Why Your Furnace Won’t Light


If your home’s heater has stopped working, it could be because your furnace is failing to ignite (or light). Without igniting, your furnace won’t be able to heat your indoor air and make your home warmer. While you may need to contact an HVAC technician to solve the ignition problem, there are also a few troubleshooting steps you can take that may fix the issue in just a few minutes.

Need furnace repair services in New Orleans or Metairie? Contact Stuart Services today! 

Furnace burner igniting


Below are some of the most common reasons why furnaces won’t light.

1. The furnace door isn’t shut correctly.

Believe it or not, your furnace’s door might be the issue. In some models, the equipment won’t run unless the door is shut all the way until it clicks or snaps.

2. The heat isn’t actually “on.”

Make sure that your thermostat is in the correct setting to heat your home. If your thermostat is set to “on” without the “heat” setting activated, this means that your system is just circulating room-temperature air. If you’ve set your thermostat to “auto,” the temperature on the thermostat may need to be a few degrees lower than room temperature for your heater to kick on.

3. Your furnace or thermostat tripped the circuit breaker.

Hardwired thermostats and furnaces with electronic ignition systems can trip a circuit breaker during a momentary power surge. Pay a quick visit to your home’s circuit breaker panel and check for any tripped breakers that need to be reset.

4. Someone closed the gas shut-off valve to your furnace.

If the rest of your home is getting gas (such as your water heater or gas range), but your furnace won’t light, then it’s possible that gas isn’t reaching your furnace. There should be a gas line leading up to your furnace with a valve on it that allows you to stop and start the flow of gas to the heating equipment.

Check the position of the valve’s handle or lever. If the handle is in line (or parallel) to the gas pipe, then it’s allowing gas to flow to your furnace. If the handle is at a right angle to the pipe or forming a “T” with the pipe, then the valve is blocking gas from flowing beyond that point. To turn the gas on, twist the handle until it’s in line with the gas pipe.

5. There’s a problem with your furnace’s gas and air mixture.

Although most people don’t realize it, a gas furnace needs the proper mixture of oxygen and natural gas to ignite safely and burn efficiently. When the proportion of gas to oxygen is off, then your furnace may have trouble igniting safely and quickly.

If your furnace “takes too long” to ignite, your furnace’s flame sensor will cut off the gas flow to your furnace to prevent a dangerous amount of gas from accumulating inside of it. While this is an important safety measure, it also means that your furnace can’t light. For this issue, there is no safe “DIY” solution, so you will need the help of a licensed and trained HVAC technician.

6. Your furnace’s flame sensor is malfunctioning.

As mentioned above, your flame sensor’s job is to stop the flow of gas to your furnace if the equipment is taking too long to ignite. However, if there’s something wrong with the flame sensor, it might be cutting off the gas flow prematurely so that your furnace can never light.

The longer a furnace runs without maintenance, the more likely a flame sensor problem becomes. Dust buildup can affect its performance, as well as carbon buildup, which can lead to rusting. Its position may also need to be adjusted over time.

Need reliable heating repair in New Orleans, Metairie, Kenner, Gretna, or the North Shore area? Don’t hesitate to call upon the experts at Stuart Services: 504-321-2079!

stuart services cta

Stuart is here when you need us!

request service today
stuart services cta