noisyWhen your furnace is working properly, you can almost forget it’s there. It just quietly does its job of keeping you warm when it is cold outside. A noisy furnace is not only aggravating, it can be a sign of a significant problem.  

If your furnace is making any loud or unusual sounds, it is important to figure out the cause as soon as possible. Continuing to use a faulty furnace could cause major damage that could require extensive and expensive repairs. Be sure to turn off the power and gas to your furnace until you can isolate the source of the noise, and call a local heating professional for help.

Identifying the Cause of a Noisy Furnace

The noises coming from your furnace can help you pinpoint the problem. You may need to describe the sounds your noisy furnace is making to the repair technician so he or she can properly diagnose the problem.

Scraping or Grinding

If you hear the sound of metal moving against metal, it is most commonly caused by one of two issues.

  1. A loose blower wheel. The blower wheel is attached to the blower motor shaft by a screw. Occasionally, a blower wheel will work itself loose and rub against the blower housing. The result is a metallic grinding or scraping sound. If left unchecked, a loose blower wheel can cause damage to the housing.
  2. A broken motor mount. A broken motor mount will cause the blower wheel to make contact with the housing. It could sound like metallic rattling or scraping.

Thumping or Vibrating

Excessive thumping or vibrating is caused by a blower wheel that is out of balance. When the blower wheel is off balance, it can cause the motor to run out of balance as well. Left unfixed, this problem can quickly escalate and cause more damage to the internal mechanisms of your furnace.

Squealing or Screeching

A high-pitched squealing sound is usually caused by insufficient lubrication, although it can also be caused by a loose fan belt. The noise can usually be remedied by either tightening the belt or applying oil. Make sure to contact a professional for expert help with these small jobs.

Banging or Popping

Loud banging or popping when the furnace starts or stops is caused by the metal ducts flexing. This could be a sign that you have a clogged filter or closed vents. Try changing your air filter and checking to make sure your vents are open and unobstructed before contacting a repair technician. If the noise continues, it could be sign that you have undersized ducts.


If you furnace makes a constant low rumbling noise, it could be a sign that you have a bad burner. If you hear a low rumbling when your furnace is running, turn off your unit and contact a professional for help.

Fixing a Noisy Furnace

If you are experiencing rackety noises from your furnace, it is best to contact a professional to rule out any major or potentially dangerous problems. Attempting to repair your furnace yourself could cause more damage and even lead to accidental injury.

However, there are a few simple repairs that any homeowner can tackle on their own.

Replace Your Filter.

Replacing an old filter with a new one is one of the simplest cures to minor furnace noise. Here are some basic step-by-step directions for replacing your furnace filter.

  1. Select an appropriate filter. There are several filter options available. Low-quality filters need to be replaced more frequently, so it may be worth the extra money to invest in a high-quality filter. If you are unsure which filter to use in your furnace, contact your owner’s manual for dimensions and guidelines.
  2. Switch off your furnace. Before you begin the process of replacing your furnace’s filter, be sure to turn off your unit to prevent any accidents.
  3. Open the furnace access panel. The access panel is usually located on the side of the furnace near the bottom of the unit.
  4. Remove the old filter.
  5. Position the new filter. After the old filter has been removed, it should be easy to slide the new on into position. Be sure to carefully follow the airflow arrows marked on your filter.
  6. Replace the access panel.
  7. Turn on your furnace.


If your furnace continues to make excessive noise after you have replaced the filter, it is time to call in the professionals. More serious repairs require mechanical know-how and experience. A certified HVAC technician can help you diagnose and fix a noisy furnace so you can rest in peace, quiet, and comfort.