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Furnace Making Sparking Noise? 4 Common Causes (+ Fixes)

Sparking sounds coming from a furnace are generally associated with electrical problems, which is why you shouldn’t allow it to go unnoticed. A furnace making a sparking noise is a sign of numerous problems, but sometimes the fix is quite easy — You just clean a few parts, and the noise is gone.

Your furnace is making a sparking noise because the ignitor can’t ignite the burners, or they’re dirty, the flame sensor isn’t working, or there are problems with the wiring. Fix the problem by replacing or cleaning the ignitor, burners, and flame sensor. Also, check the wiring in your furnace.

If you hear a sparking noise in your furnace, take appropriate action. This article will help you understand what’s causing the noise and what you can do about it. 

Ignitor Can’t Ignite the Burners

The moment you turn on the furnace, a few processes need to occur before you can enjoy warm air throughout your home. First, the gas supply sends gas toward the furnace. For the gas to enter the furnace, a valve opens up. The valve only allows a certain amount of gas to pass. Otherwise, the furnace would get too hot and overheat. 

Once the gas reaches the ignitor, it creates a spark that starts the flame. The burner’s flame is then used to heat air pulled in from the compressor.

If there’s a problem with any of the parts involved in the process, ignition can’t occur. The ignitor may still throw out sparks — resulting in the sparking noise.

How To Fix

Since multiple issues could interfere with the furnace’s ignition process, you’ll first need to determine where the problem lies. 

Here’s what you need to do:

  1. Shut off the furnace.
  2. Open the furnace.
  3. Ensure nothing is blocking the gas valve when it’s trying to open. Otherwise, there won’t be enough gas to ignite. 
  4. Check the ignitor to see if there are problems with this part. This could be due to damage to the line that provides the ignitor with gas.

A thorough check-up by a professional can also help in this situation. They can do the maintenance and provide a thorough clean. 

Debris Accumulated on the Burners

The burners are an essential part of the ignition process. The gas passes through the burner and is ignited by the ignitor. When debris collects on this part of the furnace, the furnace can’t sustain a flame. 

Just like the previous problem, the ignitor will continue creating sparks despite the lack of gas.

If the sound comes from the part of the furnace that houses the burners and you don’t see a flame, you must clean the burners. 

How To Fix

To keep things simple, start by cleaning the burners. Hopefully, this is the fix that will solve your problem. 

If that’s not enough, use fine-grit sandpaper to sand off the debris that you see on the burners. Note that the debris from the sanding will enter the burner during the process.

So, make sure you use compressed air to blow out small particles from the burner afterward.

If your furnace has removable burners, even better. You won’t have to worry about debris falling into the burners.

The video below shows you how to remove the burners and clean this part of the furnace:

Flame Sensor Isn’t Working

Apart from the burners, gas valve, and the ignitor, there’s another part you want to look at — the flame sensor. 

This sensor detects the presence of a flame on the burners. When it doesn’t detect a flame, the sensor closes the gas valve. 

After all, you don’t want the gas valve to remain open when the furnace is turned off — this would mean you’re wasting gas and sending it into your home instead, a dangerous fire hazard.

The flame sensor can become dirty, similar to the burners inside your furnace. When this happens, the sensor cannot detect the presence of flames effectively. Moreover, the sensor may have a crack — in this case, its functionality is affected negatively. 

How To Fix

You need to remove the flame sensor to determine whether this is the reason for an ignitor that sparks continuously. A faulty flame sensor may be the problem here, but sometimes it’s simply dirt causing the problem. 

Here’s what you need to do:

  1. Turn off the furnace and shut off the gas supply. This ensures that you stay safe during the process.
  2. Unscrew the panel on your furnace to gain access to the combustion chamber in the furnace. You’ll see the flame sensor inside a hole in this chamber. The sensor looks like a metal rod.
  3. Remove any screw or bolts holding the sensor in place. Pull the sensor out and place the screws, nuts, and bolts in a safe spot.
  4. Look for a debris build-up on the flame sensor. If it’s dirty, you can use the same sandpaper trick from earlier. Use fine sandpaper to remove the gas residue from the surface. Be gentle during sanding to avoid damaging the sensor.

If the sensor is cracked, you need to replace it to stop the sparking noise. Once you’ve fixed the sensor, it’ll be able to regulate the release of gas and the activity of the ignitor effectively. 

Struggling to clean the sensor? Here’s a video showing you how: 

Problems With the Wiring

Although a sparking noise is typically related to the ignitor and the burners, electrical wiring issues can make similar sounds. When trying to diagnose the issue behind the noise, you should check everything. 

There are wires all throughout the furnace. If a piece of insulation breaks off, causing a short, or if two wires touch, that can create a spark with the accompanying sound. 

How To Fix

Checking for electrical wiring problems can be a challenge as you need to know where to look. Since the furnace includes components on the outside and inside your home, you have many areas to cover:

  1. Listen closely for the sparking sound. Try to find where it’s coming from. 
  2. Mark the location and turn off the furnace. Open up the panels surrounding this area and check for problems with the wiring. 


Sparking noises coming from the furnace are not to be ignored. The noise can indicate problems with wiring. It can also be a sign that the ignitor is having trouble igniting a flame for the furnace to start working. 

A professional can quickly identify why your furnace is making a sparking noise and ensure that you stay safe before, during, and after the repairs. 


  • Vincent Steele

    Vincent is a freelance writer based in Santa Ana, California. When he isn't writing articles for Temperature Master, he can be found biking or hanging out with his cat, Shelly.